Understanding regional variability in species richness is necessary for conservation efforts to succeed in the face of large-scale environmental deterioration. Several analyses of North American vertebrates have shown that climatic energy provides the best explanation of contemporary species richness patterns. The paucity of analyses of insect diversity patterns, however, remains a serious obstacle to a general hypothesis of spatial variation in diversity. We collected species distribution data on a North American beetle genus, Epicauta (Coleoptera: Meloidae) and tested several major diversity hypotheses. These beetles are generally grasshopper egg predators as larvae, and angiosperm herbivores as adults. Epicauta richness is highest in the hot, dry American southwest, and decreases north and east, consistent with the species richness-energy hypothesis. Potential evapotranspiration, which is also the best predictor of richness patterns among North American vertebrates, explains 80.2% of the variability in Epicauta species richness. Net primary productivity and variables measuring climatic heat energy only (such as PET) are not generally comparable, though they are sometimes treated as if they were equivalent. We conclude that the species richness-energy hypothesis currently provides a better overall explanation for Epicauta species richness patterns in North America than other major diversity hypotheses. The observed relationship between climatic energy and regional species richness may provide significant insight into the response of ecological communities to climate change.

Current large-scale mammalian diversity patterns in Canada can be accurately explained using various measurement of heat energy. Unfortunately, climatic change is predicted to alter the fundamental climatic basis for contemporary diversity gradients, with the expected consequence that much of the Canadian biota will need to migrate in order to remain within climatically suitable regions. We make predictions regarding future mammal diversity patterns in Canada, and therefore provide a preliminary indication of where management intervention should be directed in order to conserve mammal diversity as climate changes. We also examine the current distributions of individual mammal species in Canada in order to determine which taxa cannot migrate farther north because of the Arctic Ocean barrier. Of the 25 species that fall into this category, we examine the predicted loss habitat in one keystone species - Decrostonyx groenlandicus, the collared lemming - and find that this taxon is likely to lose approximately 60% of its habitat with unpredictable but likely detrimental consequences for the arctic biota. We discuss the implications of our findings briefly.

Estimates of global species richness for insects are based upon extrapolations from " Known" to unknown faunas and hence rely upon accurate counts of species for the referrent taxon or region. The number of reference species depends upon the species concepts employed by workers in that group combined with the degree to which nonstandard (i.e. nonmorphological) approaches have been used. Genetic data are more directly applicable to the detection of the apparent absence of gene flow, which lies at the heart of any species concept, than is morphological information. But what criteria can be used as a practical guide to suggest the absence for gene flow and define species-level units? Minimally, the phylogenetic species concept requires that there be one fixed difference between two samples for them both to be considered discrete species. The assumptions accompying this definition include the survey for sufficient geographic locations, loci, and individuals. Based upon six studies of mostly widespead, readily identifiable and well-investigated bee "species", we estimate that the number of species currenlty recognised may underestimate the true figure by half (although for at least two of the studies localities have been undersampled and more collections are needed). Even when examples for which there are fewer than five fixed differences between samples are removed from the data set, the number of recognised species increases by perhaps as much as 50% (the same caveat regarding undersampling of populations still applies). We suggest that the presence of morpholoically unrecognised species may be more common among widespread, easily identified "species" than is generally accepted. Whether or not similar levels of species underestimation apply to other faunas, such as tropical rainforest canopy beetles, remains to be investigated.

A43

A fundamental problem in ecological research is to explain largescale gradients in species richness. Although many causative agents for this phenomenon have been suggested, the species richness-energy hypothesis has received the strongest empirical support: this hypothesis states that higher energy availability provides a broader resource base, permitting more species to coexist. Here we show that the species richness-energy hypothesis applies to North American mammals only over a limited geographical area in which climatic energy levels are low (Alaska and most of Canada), rather than on a continental scale as had previously been accetped. In relatively high-energy regions of North America, corresponding to most of the continental United States and southern Canada, we find that manmal species richness is best predicted by topographic heterogeneity and local variation in energy availability. Our results contradict previous studies of large-scale richness patterns that dismissed the importance of habitat heterogeneity and have implications for climate change research.

Results of phylogenetic analysis are frequently used to investigate the pattern of evolution of characteristics of interest. In examples such as the evolution of spider webs, the number of horns on a rhinoceros or social behavior in halictine bees, the results of phylogenetic tests may lead to traditional views being overturned. However, conclusions based upon phylogenetic analyses of evolutionary pattern require careful consideration of character coding and taxonomic sampling as indicated by studies of rhinos and HIV respectively. Phylogenetic results are less often used to direct further research, an area of their application which remains underutilized. In this paper I concentrate on the application of phylogenetics to problems of social evolution in halictine bees. There are seven genera/subgenera that are known to contain both solitary and social species and at least 9 species which exhibit behavioral polymorphism with both solitary behavior and eusociality found within the same or different populations. A priori, these taxa would seem to be the best ones to use in tests of the selective advantages of eusociality. However, results of phylogenetic analysis indicate that in the majority of cases (Halictus, Seladonia, Augochlorella and Augochlora) it is solitary behavior that is the recent evolutionary innovation and eusociality is ancestral. Use of the non-phylogenetic approach to the comparative method in each of these instances would not provide information on origins of eusociality. In contrast, eusociality appears to be derived in both the subgenera Lasioglossum (in the species L. aegyptiellum for which the limited field-collected data are presented for the first time) and Evylaeus. Overall, of the nine species for which both eusociality and solitary behavior have been recorded, solitary behavior is the recent acquisition in at least 6 cases, and the only probable case of recent origin of eusociality exhibited by behaviorally polymorphic species (Lasioglossum (Evylaeus) comagenense and L. (E.) fratellum) refers to origin of delayed eusociality. The application of phylogenetic methods to the study of evolutionary pattern suggests both which taxa are deserving of further field work and which require additional phylogenetic analysis.

A41

The social biology of Halictus ligatus has been investigated in many localities from Southern Canada to the Caribbean. In southern Florida it seems to be multivoltine and continuously brooded unlike the situation in more northerly areas where it has a more typical annual colony cycle with a moderately well established reproductive division of labor. In order to investigate the possibility of genetic differentiation between southern and northern behavioral types, samples of this species were collected along a transect from Toronto, Ontario in the north, to the Florida Keys in the South; additional samples were available from New Mexico and California. Two distinct species were found but surprisingly, their geographical ranges about far to the north of the behavioral disjunction. The two species are differentiated by no fewer than 7 fixed differences out of 34 loci surveyed using standard gel electrophorectic techniques. It is probable that true H. ligatus is the northern form and that the Southeastern species should be called either H. poeyi Lepeletier or H. capitosus Smith. The two species are sympatric along a narrow stretch around the southern end of the Appalachian Mountains. Several biogeographic hypothese are suggested which may account for the distribution of these two taxa. Further samples are required from the Southern USA, Central America and the Caribbean to differentiate these hpotheses. Comparisons of the social biology of these two species in an area of sympatry should be performed.

Patterns of demographic and social variation exhibited by the sweat bee Halictus ligatus, reveal that expression of eusocial colony organization is associated with local environmental conditions, harsher conditions promoting more classical eusociality and gentler conditions promoting diminished eusociality. We examined a variety of factors affecting body size variation of H. ligatus at a nesting aggregation near Victoria in southern Ontario, Canada during the summers of 1984, 1990 and 1991. Body size variation was associated with gender and reproductive caste as expected, and there were significant colony effects on size as well. An unexpected result was the dramatic effect of local environmental conditions on body size changes in weather pattern from year to year resulted in significant body size variation among all classes of adult sweat bees, including queens, workers, gynes, and males. In 1990 cool, rainy weather led to the production of brood with relatively small body sizes, while in 1984 and 1991, relatively dry, warm weather had the opposite effect. Weather probably influenced brood body size by affecting the ability of adult female bees to gather provisions for the larvae, and so indirectly affecting food availability to brood. Since queens are produced a year before their own workers, environmental factors affecting their relative body sizes are uncorrelated. Nevertheless, the degree of eusocial colony organization is strongly affected by variation in the relative sizes of queens and workers, and this illustrates the extent to which stochastic environmental variation strictures opportunities for behavioural interactions in primitively eusocial bees. The pattern of inverse variation between temperature and body size in this bee contradicts the general pattern of increased body size at higher temperatures generally seen in insects and other ectotherms, and indicates that social insects could be an exception to this rule.

Spermathecae of solitary and primitively eusocial bees from five major families were compared according to their chamber size, epithelial cell height (wall thickness), number and shape of glands, number of sperm pumps, and diameter of the duct, using whole mounts and serial sections. A thick spermathecal wall with a small chamber in our exemplar colletid, megachilid, and andrenid bees, a large chamber with a thick wall in social apidae, and a thin wall with a large chamber in social halictids that a big chamber may be associated with increseaed colony size. A thin epithelium in the receptacle of halictid bees suggests relegation of spermatheacal secreation to the spermathecal gland. A relatively thick spermathecal wall in th Apinae indicates the potential importance of both the epithelial cell layer of the at receptacle and the enlarged spermathecal gland in maintaining large numbers of stored sperm. There was one sperm pump in all taxa the representative Halictidae, in which this structure was paired. Elongated spermathecal glands may typify the spermathecae of eusocial bees.

We studied a nesting aggregation of the primitively eusocial sweat bee Halictus ligatus near Victoria in Souther Ontario during the summers of 1984, 1990, and 1991. Differences in local weather patterns from year to year had marked effects on bee demography and behaviour, belying previous conclusions about "typical" social organization in this aggregation. In 1990, comparatively cool, rainy weather resulted in high nest-failure and low brood-survival rates, while in 1984 and 1991, relatively dry, warm weather had the opposite effect. In 1984 and 1990, spring nest initiation was synchronous and the emergence periods of the first (worker) and second (reproductive) broods were temporally distinct. In 1991, exceedingly warm spring weather caused asynchrony in the timing of nest initiation, accelerated brood and colony development, and continuous brood production. In 1984 and 1990, a few males were produced in the first brood but most were produced in the second brood several weeks later. In 1991, continuous brood production meant that production of males represented the transition between production of workers and of gynes (second-brood females). Patterns of demographic and social variation exhibited by H. ligatus at Victoria parallel those observed on a continent-wide geographic scale. This suggests that primitively eusocial sweat bees maintain a variety of reproductive options, adjusting their social behaviour in response to local environmental conditions.

In species with haplodiploid genetic systems, full sisters are more closely related to each other and less closely related to their brothers, than to their daughters and sons. The classical theory for the origin of hymenoptern eusociality predicts that in many primitively or facultatively eusocial species, workers should exploit this relatedness asymmetry by laying male-destined eggs while allowing the queen to lay gyne-destined (reproductive female) eggs. This prediction is satisfied in many species where colonies are founded by solitary gynes. Here we describe a surprising reversal of the classical pattern. In colonies of the bee Halictus ligatus (Halictidae), queens produced most of the male destined eggs whereas workers produced many of the gyne-destined eggs. We suggest that this pattern may result from temporal constraints on the production of reproductive brood, and that it may be common among primitively eusocial species.

In this paper we test the following two hypotheses: (1) that apparently conspecific samples of the cleptoparasitic bee Coelioxys funeraria, differing markedly in size and reared from different host species, do indeed respresent one panmicitc population; (2) that bees that nest in holes in wood or twigs have higher levels of genetic variation than those nesting in the ground. Based upon 41 loci, the genetic differences between the two samples of C. funeraria could be explained entirely in terms of sampling error. In contrast, the sympatric C. moesta showed 16 fixed allelic differences from the C. funeraria samples. Similarly, the two hosts of C.funeraria, Megachile relativa and M. inermis, had 21 fixed allelic differences between them out of 42 presumptive gene loci. Heterozygosities ranging from 0.045 to 0.054. Comparisons of heterozygosity estimates among bees remain ambiguous as to whether soil nesting confers sufficient environmental buffering effects to reduce possible advantages of heterosis is ground-nesting species.

Nine nests of Lasioglossum (Dialictus) tenax were excavated near Calgary, Alberta, Canada over a time period encompassing the entire brood production period in 1988. Each nest contained a maximum of one active adult female, nest productivity peaked in mid July, protandry was noted detected. These data suggest that this species is solitary. These results are compared with data for the sympatrically nesting eusocial species L. (D.) Laevissimum.

Caste determination in primitively eusocial sweat bees is thought to be due to an interacting suite of factors, including size of the larval provision mass, time of year, and social context of the nest into which a young female emerges. Newly emerged workers, suggesting the existence of larval caste determination cues. Since photoperiod, temperature, and interactions with nestmates were unlikely to affect larval caste determination, we compared the sizes and contents of larval provision masses destined to produce either workers or gynes. Gyne-destined larvae consumed pollen masses that were larger and contained slightly more sugar that those of worker-destined larvae. We suggest that sugar content is one cue with prompts the development of fat reserves in gyne-destined females but not in worker-destined females. The amount of fat possessed by a newly emerged female influences her chances of successfully entering diapause shortly after emergence. Therefore, small, lean females may be more susceptible to behavioural control by queens and more likely to become workers, while large, fat females would be more likely to become gynes.

Lasioglossum laevissimum was studied in Calgary, Alberta, where it is eusocial with one worker brood. Estimates of relatedness were obtained among various categories of nestmate based upon four polymorphic enzyme loci, two of which exhibited significant levels of linkage disequilibrium. Relatedness estimates among workers and among reproductive brood females were very close to the expected 0.75 value that obtains when nest are headed by one, singly mated queen. However, relatedness between workers and the reproductive brood females they reared was significantly lower than 0.75. A low frequency of orphaning with subsequent monopolisation of ovipositon by one work brood female in orphaned nests may explain these results. Workers were significantly more and queens significantly less closely related to make reproductives than expected if all males were to have resulted from queens significantly less closely related to male reproductives than expected if all males were to have resulted from queen-laid eggs. Orphaning and worker-produced males contribute to this result. The sex investment ratio was 1:2.2 in favour of females in excellent agreement with the predictions based upon relative relatednesses between workers and reproductive brood males and females. Adaptive intercolony variation in investment ratios was detected: the sex ratio was more heavily female-biased in nests in which the relative relatedness asymmetry between workers and reproductive brood was more female-biased. The study species is the most weakly eusocial hymenopteran for which relatedness estimates and sex ratio data are available. With high relatedness among nestmates and a strongly female biased sex ratio, this study suggests the importance of indirect fitness contributions in the early stages of social evolution.

We investigated the phylogientic relationships of the chytridiomycota and the chytridomycetous gut fungi with a cladistic analysis of 42 morphological, ultrastructural, and mitotic characters for 38 taxa using both maximum parsimony and distance algorithms. Our analyses show that there are three major clades within the chytridiomycota: the gut fungi to the order Neocallimasticales ord.nov. Our results suggest that a modified chytridiales, including the Monoblepharidales, is a monophyletic group. In contrast the Spizellomycetales are papraphyletic because the Chytridiales arose within them. The separation of the traditional Chytridiales into two orders is thus doubtful. Although the Blastocladiales are closer to members of the Spizellomycetales than the Chytridiales, the cladistic analyes of both structural and rRNA sequence data do not support the idea that the Blastocladiales were derived from the Spizellomycetales. We suggest emendations to the classification of the Chytridiomycota and note which groupings require further analysis. Our Phylogeny for the currently recognized species of gut fungi is inconsistent with the existing classification. Nonetheless, pending further investigations, we prefer to retain the existing, easily defined genera for which a key is provided.

Sibling species pairs of sweat bees (Halictus confusus and H. tumulorum) and pine sawflies (Neodiprion pratti and N. marus) were surveyed for genetic variability using enzyme eletrophoresis. Levels of hetero-zygosity were found to be within he ranges earlier recorded for Hymenoptera. Expected heterozygosities were not significantly higher in the sawfiles than in the sweat bees. Eztimates of genetic identity between the siblings species were not lower than those generally found for diplodiploid insect species: no evidence was found for an increased rate of evolution in these haplodiploids. Genetic identity data among populations of H. confusus and between Halictus species were within the range expected for conspecific popluations and sibling species, respectively. In Neodiprion all genetic distances were low but the two populations of N. pratti had similar genetic distances as each did to N. maurus, indicating the neccessity for further systematic studies of the genus.

Two new species of halictine bees are described. A distinctive new species from high altitude in Ecuador is described on te basis of a single male. It appears to fall within the genus Caenohalictus as presently understood, although this diverse genus is badly in need of revision and may not be monophyletic. The concept of Mexalictus is expanded to include a new subgenus, Georgealictus, which appears to be an epiponine wasp mimic with a petiolate abdomen and elongate propodeum. This new subgenus is the sister-group to the nominate subgenus of Mexalictus. Mexalictus (Georgealictus) poludbiodes is described on the basis of one male and two females, all from altitude in the state of Chiapas, Mexico.

DNA fingerprints (DNAfp) were obtained for three widely separated samples of bee related to Lasioglossum marginatum using the M13 sequence as a probe. Bee samples were obtained from France (three localities separated by at most 20 km), Greece and India. All European populations exhibited almost identical profiles with similarity indices (S) of over 98% within a French sample, 94% among Greek bees and 90% between Greek and French bees. The DNAfp profiles of Indian bees showed more polymorphism (intrapopulation S = 77%) and were quite dissimilar to the European samples (S = 55% and 56% to French and Greek samples, respectively). The similarity between populations separated by over 2000 km is higher than among unrelated individuals within a population in two other bee species and the tsetse fly. Data from allozyme electrophoresis shows parallel variation to that obtained with DNAfp and the genetic differences between Indian and European samples are strikingly large (Indian and European populations shared no alleles at 14 out of 47 loci surveyed) such that more than one species must be involved. Nonetheless, the samples are indistinguishable morphologically. We argue that chronically low effective population size in these species results in low levels of genetic variability and that this, combined with a genetic bottleneck during the speciation event and colonization of Europe, may have resulted in both the extremely low levels of DNAfp variation in European bees and the large number of fixed allelic differences between Europe.

Allozyme variation at an average of 37.3 loci was assessed in queens of 16 Bombus and 2 Psithyrus bumble bee species from North America. The mean expected heterozygosity (H) for the Bombus species was 0.008 " 0.006 (95% confidence limits) and that for the Psithyrus was 0.007 " 0.007. These levels are significantly lower than found in other Hymenoptera but are comparable to those found in previous studies of bumble bees based on far fewer loci. Neutral mutation and random genetic drift can account for the observed variation, but this implies a very small effective population size for species of bumble bees.

An aggregation of Lasioglossum (Dialictus) laevissimum was studied in Calgary, Alberta, in the summer of 1988. This species was weakly eusocial, with an average of less than 2.5 workers per nest, 43% males in the worker brood, 63% of workers with well developed ovaries, 35% of them mated, and a mean queen-worker size dimorphism of 7%. Based upon its average rank for these variables, in comparison with eight other species, L. laevissimum is the most weakly eusocial member of the subgenus Dialictus. Nonetheless, reproductive-brood production averaged around 25 per nest, and this species is clearly well adapted to short-summer environments. There was little evidence that any worker-brood females entered early diapause rather than functioning as workers. A few spring nests were initiated by more than one overwintered foundress. These pleometrotic nests often had worker-brood productivities that exceeded average reproductive-brood size. Brood mortality was low, infection of provision masses after rainfall being the major factor.

We show that Lasioglossum mediterraneum (Blüthgen) (Hymenoptera, Halictidae) is a species distinct from L. laticeps (Schenck) based upon electrophoretic analysis of 39 allozyme loci for sympatric populations collected from the Dordogne region of France. The genetic identity between the two is below average for sibling species of insects: no fewer than 10 fixed allelic differences were found. In contrast, allopatric L. laticeps populations (from the Dordogne and Paris) are genetically almost identical (I = 0.998). Heterozygosity estimates for both species are low, as is often the case with Hymenoptera. Diagnostic characteristics that can be used to separate the two species are described. A phylogeny for nine species of the subgenus Evylaeus is constructed from allozyme data.

Hymenoptera typically have low levels of allozyme variation yet genetic markers are required for studies of relatedness. Results of a survey of allozyme variation in the order are presented. Data were analysed both in terms of the proportion of times variation has been found with particular enzyme-staining systems and the average heterozygosity detected with each system. Some of the most frequently variable enzymes have not been routinely surveyed. Some possible reasons for this are discussed and some technical improvements are suggested.

A23

Phylogenetic studies are required to establish the direction of evolutionary change in behavioral characters. Here I produce a phylogeny for 8 Old World species of the subgenus Evylaeus based upon cladistic analysis of 26 informative allozyme loci. By mapping behavioral character states upon the resulting cladogram, the following major conclusions could be drawn: (1) Social Evylaeus species share sociality by descent from a eusocial common ancestor which might not have been an Evylaeus species; the solitary behavior of Lasioglossum (E.) fulvicorne may be a derived condition. (2) One reversal to solitary behavior within Evylaeus is proven for a Japanese montane population of L. (E.) calceatum. (3) The perennial societies of L. (E.) marginatum are derived from an annual social cycle and do not represent an independent evolution of sociality. (4) Multiple-foundress associations are a derived condition within Evylaeus, suggesting that if social behavior evolved within the group, then the semisocial route was not the one taken by these bees. (5) The nest architectural trait of excavating a cavity around clustered brood cells is a ground plan characteristic of Evylaeus but with a reversal in L. (E.) marginatum. (6) It is likely that extended opening of brood cells during juvenile development has originated independently twice among the species considered. Another benefit of phylogenetic studies is their use in predicting which taxa are most likely to exhibit particularly interesting behavioral states. In this regard, the phylogeny suggests that close relatives of L. (E.) fulvicorne and also most of the major species groups of Evylaeus which have not received any field study should be investigated both phylogenetically and behaviorally for a full evaluation of behavioral evolution in Evylaeus.

Augochlorella striata was studied at the northern limit of its range. The study population contained a mixture of solitary and social nest foundresses. Eusocial foundresses produced 1 or 2 workers before switching to a male biased brood. Solitary foundresses produced males first. Cells vacated by enclosed offspring were reused late in summer. A female biased brood resulted from cell reuse in both solitary and eusocial nests. Workers were slightly smaller than their mothers and were sterile although most of them mated. In comparison to published data from a Kansas population of this species, the Nova Scotia population had i) a lower proportion of multiple foundress nests, ii) a smaller worker brood and iii) a briefer period of foraging activity but iv) comparable overall nest productivity.

A population of the primitively eusocial bee Augochlorella striata was surveyed for allozyme variation at 47 loci for 35 enzyme systems with a mean number of haploid genomes sampled of 76 per locus. The expected heterozygosity (mean " S.E.) was 0.107 " 0.004, the highest found for any bee species, solitary or social, studied to date. This result indicates that low levels of genetic variation are not ubiquitous in bees. No differences in allele frequencies between males and females were found. One diploid male was detected providing a maximum likelihood estimate of the frequency of diploid males in the population of 2.6 per cent. Strong linkage disequilibrium was detected between the loci Dia-2 and Lap. Under a genetic drift explanation for disequilibrium and realistic assumptions for the recombination rate between the two loci, the predicted population size is in broad agreement with that suggested from field studies.

Halictus rubicundus (Christ) is a primitively eusocial halictine bee. Studies of electrophoretic variation at 48 loci for 37 enzymes with an average of 38 bees per locus provided an expected heterozygosity of 0.038 " 0.018 for a population from Vancouver, B.C. This value is well within the range found for other primitively eusocial bees and wasps. Comparisons of allozyme mobilities made among samples from France, Alberta and Vancouver indicated that there are some genetic differences, with the French sample appearing particularly distinct. The loci Diaph, G3pdh-1, and 6Pgd-1 had variants with both alleles at high frequency within the Vancouver population. These loci could provide good estimates of the average relatedness between nest mates.

Augochlorella striata, Lasioglossum (Evylaeus) cinctipes, Lasioglossum (Evylaeus) comagenense, and Lasioglossum (Dialictus) laevissimum were studied on Cape Breton Island, Nova Scotia, throughout their flight season in 1987. The weather during the summer was unusually good, with above-average temperatures and hours of sunshine but very low rainfall. Conversely, the previous summer had been very poor for bees, with comparatively few days suitable for foraging, particularly in July. Augochlorella striata was basically solitary but some nests produced one or, at most, two workers, thereby becoming eusocial. In other localities, L cinctipes is known to be eusocial with well-developed morphological and physiological caste differentiation. However, most foundresses observed in 1987 were extremely small, smaller than usual for workers elsewhere, and none of the more than 100 nests produced adult workers or a reproductive brood. Most foundresses were either survivors of the worker brood from the previous year or unusually small reproductive brood females produced as a result of the bad weather in 1986. Lasioglossum comagenense was solitary or semisocial with one to four females occupying a nest. Lasioglossum laevissimum exhibited significant levels of pleometrosis and an extended period of worker foraging in summer. A comparison of the productivities of these four species indicates the importance of a flexible social system in a marginal climate.

The nest architecture of four species of the bee family Halictidae from Cape Breton Island, Nova Scotia, was studied. Augochlorella striata and Lasioglossum (Evylaeus) comagenense constructed their brood cells in a cluster surrounded by a cavity. In the case of A. striata, the cavity-forming habit increased the rate at which the soil of the brood cell cluster dried out, relative to the surrounding soil. The year of the study was unusually dry and in midsummer the moisture content of the soil was extremely low. This weather pattern seemed to result in some mortality of A. striata brood due to dehydration, and prevented foundresses from constructing brood cells. The two other species, Lasioglossum (Evylaeus) cinctipes and Lasioglossum (Dialictus) laevissimum, did not construct brood cell clusters. All four species had shallower nests than other species with similar nest architectures for which published data are available. All species except L. laevissimum nested in association with stones at the ground surface. It was shown that brood cells of nests situated close to rocks and stones were likely to experience increased temperature, presumably resulting in a faster developmental rate of immatures. This may be important in the Cape Breton environment, which is clearly marginal for social sweat bees. Both A. striata and L. comagenense exhibited very low mortality rates in developing immatures (1 and 7%, respectively).

The biology of Evylaeus villosulus was studied both in the field and in experimental rearing cages.

Field caught females and their summer daughters were compared using multivariate discriminant functions analysis. The variables used were two size, two colouration and four sculpturing characteristics. All variables show significant differences between generations but the colouration and sculpturing characters did not show allometric variation within generations and may be environmentally induced.

Sex ratio data are available for the summer generations for both field and laboratory reared brood. Both gave female biased sex ratios approximately 4:1. Data for the overwintering generation were obtained only for the laboratory, the sex ratio was slightly female biased 1.2:1. Pupal weights differed significantly between generations for females but not for males. Using the appropriate values, the investment ratio is female biased in both generations; approximatley 5:1 in the summer and 2:1 in the autumn.

Overwintered females frequently survive long enough to forage simultaneously with their earlier emerging offspring. Cohabitation between females of the same generation occurs with low frequency but no division of labour results, rather communal colonies are formed. Similarly, when a mother and a daughter shared a nest, an eusocial colony resulted. Thus, E. villosulus would appear to be a basically solitary species despite exhibiting reduced size in the daughters of overwintered females and a female biased sex ratio, both of which are characteristics frequently associated with eusociality.

A nesting aggregation of Lasioglossum (Evylaeus) cooleyi (Crawford) was studied on the campus of the University of British Columbia in July 1988. This species is primitively eusocial. There was a 7.3% size difference between queens and their workers; 40% of the latter had well-developed ovaries and 14% were mated. Thus, this species is one of the most primitively social members of its subgenus. The cells were not gathered together in a cluster or surrounded by a cavity. This species has a haploid chromosome number of 18, the largest number yet recorded for any Halictid bee.

Two factors were important in causing brood mortality in a southern Ontario population of Halictus ligatus: parasitism by larvae of the bombyliid Bombylius pulchellus and various forms of microbial infection of bee immatures or their pollen ball food. Bombyliid larvae consumed host prepupae or, less commonly, young pupae, restricted their attack mostly to the reproductive brood, and were contagiously distributed within the nest population. All immature stages were susceptible to fungal infection or disease but such pathogens did not seem to spread among cells within nests, indicating that bees may be able to prevent the spread of disease from one brood cell to another. Filling affected cells with earth may accomplish this brood hygiene. The survival rate of worker and reproductive brood immatures approximated 90%. Reproductive brood mortality affected females more than males. Reproductive brood mortality was probably underestimated: filled-in cells that may represent brood mortality were not included in these estimates.

In north temperate regions Halictus ligatus has an annual colony cycle as found in almost all other social sweat bees. However, in the extreme south of Florida, this species is continuously brooded and multivoltine (i.e., it has overlapping colony cycles with one complete cycle lasting for a few months) and the matrifilial societies exhibit a markedly reduced reproductive division of labour. Several series of collections were made along the length of Florida to determine where the transition between the annual and continuously brooded colony cycles occurs. An annual colony cycle seems to be retained at least as far south as Tampa; the continuously brooded populations are restricted to the extreme south of Florida.

Two single cell nests of Megachile brevis pseudobrevis are described from the Florida Keys and compared with the nests of the nominate subspecies. Both cells contained pupae of the meloid beetle Nemognatha (Pauronemognatha) punctulata. This is the first record of a larval host for this species. The triungulin larva of N. punctulata is described and a key to the first instar larvae of the subgenus Pauronemognatha is presented. Observations indicate that Borrichia frutescens is the preferred host plant for the meloid adults and it seems probable that they oviposit mostly on this species.

A large population of Halictus ligatus was studied in the subtropical climate of Knights Key, Monroe County, Florida. The dissection of 858 female bees caught on flowers and 420 bees from completely excavated nests gives the following picture of phenology, colony development and social organisation. In the Florida keys, H. ligatus is continuously brooded and multivoltine. However, towards the coldest time of year young gynes may rest in their natal nests rather than found a new colony. This may result in a partial synchronisation of nest initiation when warm weather returns after a particularly cold spell. Most nests are started by a single foundress that usually survives until near the end of production of reproductives. The first brood is very variable in size and males average 11% of the bees produced at this stage. This figure increases to 56% when the first brood workers begin provisioning. Queens are produced some time after the rise in male production and colony longevity is extended by the presence of some worker brood during this phase. Queens average 16% larger than their workers but appear to exert little inhibition of worker reproductivity: 57% of worker bees mate and 68% show ovarian development. This population is unique amongst social halictines in being continuously brooded, multivoltine and in having such weak physiological caste differentiation. It seems to represent an intermediate stage between the primitively eusocial colonies of H. ligatus found in temperate regions and the communal-like ones of the tropics.

In the subtropical climate of the Florida Keys, Halictus ligatus has a continuously brooded, multivoltine colony cycle. This results in young gynes and workers being active at all times of the year, potentially causing problems for males with respect to mate choice. Males respond to females by ignoring them, touching them briefly or by knocking them of flowers into the surrounding vegetation, where mating takes place. Over half of the females at this locality are mated although males prefer large, young individuals. Multiple mating of females does occur. Males search for females around flowers and, less commonly, near nest sites. Because females of this social insect offer varied returns to male mating effort, it is not surprising that males exhibit mate choice.

Intraspecific cleptoparasitism is described in a subtropical population of the social sweat bee Halictus ligatus. Cuckoo-like individuals are, on average, larger than workers but smaller than queens. Behavioral modifications resulting in the cleptoparasitic behavior are quite minor: forced entry and sneaky oviposition are activities possessed by non-parasitic members of this population. Only the trap-lining and host nest choice behaviors are new. Intraspecific cleptoparasitism has not been recorded from any of the temperate populations of this species that have been studied. It is argued that the continuously brooded, multivoltine phenology of this population has been a necessary prerequisite for the origin of this pattern of cleptoparasitism.

The social organisation of Halictus ligatus was studied at Victoria, southern Ontario. At this locality, the one worker brood has a protracted period of emergence; this results in small colony populations throughout the summer activity phase. Workers average 12.7% smaller than their queens, 60% of them have some ovarian development, and 42% of them mate. More males are produced toward the very end of the first brood than earlier in the spring provisioning phase. These late first brood males probably survive to mate with reproductive brood females. In orphaned nests, one worker dominates the others to become a replacement queen. Most replacement queens are mated and orphaned colonies produce reproductives of both sexes. Data from this population are compared with those of other studies of this, and other, halictine species.

Thirteen pleometrotic (multiple-foundress) nests of the primitively social sweat bee Halictus ligatus were excavated in the summer of 1984 at Victoria, near Toronto, southern Ontario. Subordinate foundresses were significantly smaller than both dominant females in pleometrotic nests and females that nested solitarily. Most subordinates were smaller than the workers that they helped to raise. These small females could have been surviving workers from the previous summer or the offspring workers. It seems likely that they were malnourished reproductive brood individuals produced as a result of parental manipulation. In successful nests, the number of workers produced was positively correlated with the number of founding females such that productivity per foundress remained fairly constant. Pleometrotic nests also produced more reproductives than haplometrotic (single-foundress) ones. Subordinates may occasionally lay reproductive brood eggs. The increased productivity of multiple-foundress nests was not quite sufficient, by itself, to select for subordinate behaviour. The small subordinates had lower potential productivities in comparison to the larger females. This decreased reproductive potential, when combined with the increased productivity of pleometric nests, was sufficient to make subordinate behaviour selectively advantageous. When both factors are taken together, subordinate behaviour is selected for as long as the coefficient of relatedness between dominant and subordinate individuals is greater than ¼. This indicates that high coefficients of relatedness are not necessary for pleometrosis to be selectively advantageous under the conditions found in this study. Dominant females may suffer increased reproductive competition from their numerous workers. This, plus the difficulty of ensuring association with siblings in spring, may be the reason why multiple-foundress associations were uncommon at this locality. The data presented here are compared with those from other studies of this species. The factors promoting pleometrosis in halictines are compared with those that result in multiple-foundress associations in temperate polistine wasps.

Nest architecture of Halictus ligatus was studied at Victoria, southern Ontario; over 130 nests were excavated in 1984. The most important findings are as follows. Nest failure was lower in vegetated areas than in bare ground. Nests with entrances hidden under leaves may suffer less mortality from parasites than those out in the open. Loops around cells are dug in response to moist soil conditions and appear to be an intermediate step toward cavity formation. Brood mortality due to mould seemed to result from cell waterlogging which the excavation of loops may help to prevent. Cells near the surface may suffer from waterlogging after heavy rains. Nests situated in denser vegetation suffered less mortality from mould. Gyne-producing cells are larger than male or worker-producing ones. Mandibular wear is an accurate measure of the amount of excavation performed by an individual female.

Eleven behavioural characteristics of eight species of the subgenus Evylaeus were analysed using principal components analysis. The first component axis represents social level and explains over forty percent of the total variation in the data. The following characteristics are highly correlated with social level – (i) a reduction in the proportion of males in the first brood, (ii) a reduction in the proportion of workers that mate, (iii) a reduction in the proportion of workers that have developed ovaries, (iv) an increase in the mean number of workers, (v) increased contact between adults and developing brood and (vi) an increase in the size difference between queens and workers. Because these factors appear, in general, to be under the control of the queen it is argued that parental manipulation has been an important component of social evolution in the bees. The number of worker broods and the mechanism of male production are also related to social level but are less important. Nest architecture, nest defense, and polygyny seem to be unrelated to social level. Variation in nest architecture may be in response to edaphic features of the substrate. The lack of any relationship between polygyny and social level implies that the semisocial route to eusociality was not the one taken. It is likely that polygyny can only occur where the substrate is suitable for the winter hibernation of sisters in their natal nest. Multivariate methods are useful in determining the relative social level of closely related halictine species.

A nesting aggregation of Lasioglossum (Dialictus) exiguum and Halictus hesperus was discovered in the state of Chiapas, Mexico in January 1985. Both of these species are primitively eusocial with well developed morphological and physiological caste differentiation. H. hesperus has been studied in Costa Rica and Panama and details of the biologies of the different populations are compared. The social organisation of L. exiguum is compared with that of its close relative L. umbripenne. Philanthus gibbosus is recorded as a predator upon both halictine species and Trachypus gracilis preyed upon H. hesperus.

Phenologic and geographic variation in background colouration and hind wing spotting in the Satyrid butterfly Pararge aegeria are described from a study of cabinet specimens. This species has two generations in the year. The spring generation exhibits a bimodal pattern of emergence: those individuals which overwinter as pupae emerging earlier than those which pass the winter in the larval state. These early and late spring broods exhibit statistical phenotypic differences which seem to become obscured in the summer generation. Butterflies from Ireland and the South-West Peninsula are statistically distinct from those in the rest of Great Britain. A comparison between the ecological genetics of this species and Maniola jurtina is made.

An aggregation of Lasioglossum (Evylaeus) laticeps (Schenck) was discovered on the cliffs at Charmouth, Dorset, where nests were initiated in cracks in the clay soil. The cell clusters of both spring and summer broods were surrounded by a cavity which was enlarged as the number of cells increased. L. (E.) laticeps appears to have the most primitive social organisation of the four species of the L. (E.) malachurum species group for which data are available. Thus there is a high proportion of males in the first brood (24 %) and the morphological caste differences are slight: workers are, on average, 7 % smaller than the queens.