Sheila Colla

Ph.D. candidate, York University
Honours B.Sc. in Biology, University of Toronto, St. George
Email: collasheila@gmail.com

Research Interests

Sheila is pursuing a PhD in Biology at York University under the supervision of Dr. Packer. Her projects include determining to what extent the Rusty-Patched bumblebee (Bombus affinis) has declined throughout its native range and how bumblebee species diversity has changed in southern Ontario, Canada over the past 100 years.

She is also interested in determining habitat associations and requirements for each eastern species in order to aid future conservation efforts. The possible causes for decline which she is currently looking into include pesticide use, disease susceptibility, habitat loss and climate change.

For more information, please visit her website, SaveTheBumblebees.


  • Kerr JT, Pindar A, Galpern P, Packer L, Potts SG, Roberts SM, Rasmont P, Schweiger O, Colla SR, Richardson LL, Wagner DL, Gall LF, Sikes DS, Pantoja A. 2015. Relocation risky for bumblebee colonies-Response. Science 350: 287. doi: 10.1126/science.350.6258.287 Full text
  • Kerr JT, Pindar A, Galpern P, Packer L, Potts SG, Roberts SM, Rasmont P, Schweiger O, Colla SR, Richardson LL, Wagner DL, Gall LF, Sikes DS, Pantoja A. 2015. Climate change impacts on bumblebees converge across continents. Science. 349: 177-180. doi: 10.1126/science.aaa7031 Full text
  • Colla SR, Gadallah F, Richardson L, Wagner D, Gall L. 2012. Assessing declines of North American bumble bees (Bombus spp.) using museum specimens. Biodiversity and Conservation 21(14): 3585-3595. doi: 10.1007/s10531-012-0383-2
  • Szabo N, Colla SR, Wagner D, Gall L, Kerr JT. 2012. Do pathogen spillover, pesticide use, or habitat loss explain recent North American wild bumblebee declines? Conservation Letters 5: 232-239. doi: 10.1111/j.1755-263X.2012.00234.x
  • Bartomeus I, Ascher JS, Colla SR, Wagner D, Danforth BN, Kornbluth S, Winfree R. 2011. Climate-associated phenological advances in bee pollinators and bee-pollinated plants. Proceedings of the National Academy of Sciences 108: 20645-20649. doi: 10.1073/pnas.1115559108
  • Owen RE, Otterstatter MC, Cartar RV, Farmer A, O'Toole N, Colla SR. 2012. Significant expansion of the distribution of the bumblebee Bombus moderatus (Hymenoptera: Apidae) in Alberta over 20 years. Canadian Journal of Zoology 90:133-138. doi: 10.1139/z11-114
  • Colla SR, Ascher J, Arduser M, Cane J, Deyrup M, Droege S, Hall G, Henne C, Gibbs J, Griswold T, Neff J, Jean RP, Rightmyer M, Sheffield C, Veit M, Wolf A. 2012. Documenting persistence and absence of eastern North American bee species to 1990-2009. Journal of the Entomological Society of Kansas 85: 14-22. doi: 10.2317/JKES110726.1
  • Colla SR, Dumesh S. 2010. The bumblebees of southern Ontario: notes on distribution and natural history. Entomological Society of Ontario 141: 38-67. Online full text
  • Colla SR, Ratti CM. 2010. Evidence for the decline of the western bumble bee (Bombus occidentalis Greene) in British Columbia. Pan-Pacific Entomologist 86: 32-34. doi: 10.3956/2009-22.1
  • Ratti CM, Colla SR. 2010. Discussion of the presence of an eastern bumble bee species (Bombus impatiens Cresson) in western Canada. Pan-Pacific Entomologist 86: 29-31. doi: 10.3956/2009-19.1
  • Colla SR, Willis E, Packer L. 2009. Can green roofs provide habitat for urban bees? Cities and the Environment 2: 1. Full text
  • Williams P, Colla SR, Xie Z. 2009. Bumblebee vulnerability: common correlates of winners and losers across three continents. Conservation Biology 23: 931-940. doi: 10.1111/j.1523-1739.2009.01176.x
  • Colla SR, Packer L. 2008. Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson. Biodiversity and Conservation 17: 1379-1391. doi: 10.1007/s10531-008-9340-5 Full text

Favorite Recipe

Hot Chocolate

[Hot chocolate]


  • In a small saucepan, add 2 tbsp for high quality cocoa powder, a pinch of salt, 1 tbsp of Horlicks Malt Powder (optional), a pinch of crushed vanilla beans or ½ tsp of vanilla extract and 1 tbsp of cane sugar.
  • Add 2 tbsp of water and heat until boiling and dissolved.
  • Simmer for 2 mins, then add 2 cups of milk. Heat until warm.
  • Ingredients can also be substituted with cinnamon, peppermint extract, almond milk, maple syrup, or even chili powder!

Funniest Research Story


Things people have said when they saw me surveying bumblebees on flowers around the city:

  • "Why? Don't they sting?!!"
  • "Are you going to make jewelry out of them?"
  • "Why don't you study butterflies instead?"
  • "Are you removing them because they are hurting the flowers?"
  • "There's more than one type of bee???"
  • "I saw a bumblebee once down the road/in my backyard/ around the corner/on a flower, etc."
[Laurence in a good mood]
Dr. Laurence Packer
Ph.D. (Toronto)
Professor of Biology
416-736-2100 ext. 22663
[Packer Collection @ York University]
[Biology Department @ York University]
Lumbers Building 345
York University
4700 Keele Street
Toronto, Ontario
M3J1P3, Canada