The Home Bug Garden in July: Rain, Mosquitoes & Bumblebees

 My apologies to any regular readers for the long dearth in postings. This has been a miserably cool and wet summer in the Edmonton region, and along with the drain of a minor illness and the usual overwhelming nature of the field season, energy for any extra musings has been low. There have been lots of insects in the HBG, but mostly millions of mosquitoes (I’ve identified 11 different species so far).

 Even with the best intentions, though, and an amazement at how many different kinds have been seeking my blood, it is difficult to summon the energy to write appreciatively about mosquitoes and even more difficult to identify them from a picture. Instead, one must kill them carefully – no swatting or the hairs and scales needed to determine species will be knocked off – and take them to a microscope and an identification tool. If you live in Canada, the Canadian Journal of Arthropod Identification has an excellent pictorial key produced by Aynsley Thielman and Fiona Hunter of Brock Univerity in Ontario. 

 Only female mosquitoes drink our blood and only when they can. Both sexes will feed on nectar and other sources of sugary food such as honeydew or damaged fruit. Cool wet weather also favours aphids, so there is plenty of honeydew around, and discourages harvesting cherries from wet dripping trees. I haven’t actually seen any mosquitoes feeding on the cherries damaged by the house sparrows or blown to the ground by the storms, but it wouldn’t surprise me.

 The unending rains and mostly low daytime temperatures may have found favour with the mosquitoes and aphids, but I suspect many of the other insects have been reacting to the La Niña weather more like I do. The number and variety of bees has seemed to be unusually low and less energetic than usual. One bit of good news: the umbrella over the mud dauber nest seems to have been a success. The Ancistrocerus waldeni has covered the entire face of the rock with cells and, at least as of last Tuesday, she could still be seen working away.

 Bumblebees, of course, are able to fly and forage under a wider range of weather than most other bees, and the HBG Bombus have been apparent whenever the rain wasn’t actually falling. The diversity is similar to previous years, but the numbers may be lower.

 The Yellow-banded Bumblebee (Bombus terricola) was apparent early in the season, but seems rare now. A variety of tricoloured bumblebee queens (Bombus ternarius, huntii, centralis) began showing up not long after that and workers of “The Tricoloured Bumblebee” (B. ternarius) and B. centralis (which seems to have missed out on a common name) are still foraging along with numerous Half-black Bumblebees (Bombus vagans), which show up somewhat later. Finally, a large and mysterious mostly yellow queen began foraging in late July (possibly a Bombus (Bombias) species).

 The life of a bumblebee worker is short and sweet. Well, certainly short (2-4 weeks is commonly reported), and I hope the nectar helps to make the constant toil sweet. As well as working themselves to death, bumblebees have numerous parasites, predators, and diseases. Ailing workers are starting to show up in the HBG. There is a tendency to assume that some poison is at work here, but we rarely used chemicals and the City certainly hasn’t been spraying for adult mosquitoes. So, it is more likely a ‘natural’ death that is starting to claim workers.

 One common and swift end for bumblebee workers is being bitten in the neck by crab spiders. Misumena vatia is the common one in the HBG. Although I feel protective about my bees, I usually let the spiders go about their business. On Canada Day, though, my wife took a picture of one such spider bee-feast and noticed that the dined-upon bee had a couple of mites hanging out on its shoulder. I immediately dashed out and wrestled the bee away from the spider. The spider was definitely upset, the mites seemingly oblivious, but I was delighted because it gave me an opportunity to use an online key for something other than a mosquito. Barry OConnor and Pavel Klimov at the University of Michigan provide this resource for bee mites of many kinds. The long and the short of it: these two unfortunate victims were Parasitellus talparum (Oudemans, 1913). Originally described from the nest of a mole, these mites are probably predators of other small invertebrates in the bee nests and so probably good for the bees.

For more about bumblebee mites in Alberta:

Richards LA & KW Richards. 1976. Parasitid mites associated with bumblebees in Alberta, Canada (Acarina: Parasitidae; Hymenoptera: Apidae). II. Biology. University of Kansas Science Bulletin. 51(1): 1-18.