Sunday, November 14, 2010
Aculeata Agonistes: Bumbling among the Bombus
Although a few flowers are still defrosting on sunny days, it has been several weeks since the last greedily feeding queen bumblebee has been active. Or rather, I should say ‘bumble bee’ not ‘bumblebee’, because I don’t want to upset any entomologists. Bug people have a simple rule about names with a bug in them: if the common name is technically correct, then keep them separate; if not, merge them. Hence the dragonflies and damselflies in the last post are merged. They are not true flies (= Diptera), but bumble bees and honey bees are true bees (= Apoidea), so keep them separate.
I admit that I’m not always properly pedantic about bees (bumblebee has ruled on this blog) and sometimes it can get perplexing. For example, what to do about a ‘bee fly’: a fly true, but a bee not. I guess the noun used as a noun trumps the noun used as an adjective, so bee fly it is. Then there is the ‘fly bee’ that adorns Small Farm Canada’s otherwise exemplary editorial “Bee-ware” (Nov-Dec 2010, p. 13 in hard copy) about the importance of bees as pollinators and their apparent decline in abundance. Unfortunately, the picture of a bee in a pasture is actually a hover fly, probably the Drone Fly (Eristalis tenax), a mimic of honey bees. A mistake like this really bugs entomologists, but probably makes life easier for the fly.
Technically, calling a fly a bee is a big time taxonomic failure that you can quantify if you’d like using the Myrmecos Taxonomy Fail Index. Perhaps more importantly, if you can’t tell a hover fly from a bee, then you may not notice if your bees start disappearing. Many flies are pollinators, especially of easily accessed flowers like daisies or apples, but in general bees are what you want to see visiting flowers, at least if you want to maximize your production. Also, many structurally complex flowers require bees for pollination. For example those interesting pea-like flowers that adorn legumes (e.g. alfalfa, clover, peas, beans, lentils, peanuts) usually need a bee that knows how to pry apart the petals to get at the goodies. Then there are those crops with specialized anthers that require buzz-pollination (e.g. tomato, egg plant, blueberries). Nature is full of strange pollination syndromes and bees are integral to many. Even seemingly simple flowers, e.g. those of squash, have bees that specialize on them.
How much we may be hindering wild bees is a question now being asked, but one that is difficult to answer. A recent study using museum specimens (Grixta et al. 2009. Biological Conservation 142: 75-84) came to the conclusion that half of the bumble bee (Bombus) species historically present in the state of Illinois had become locally extinct or highly reduced. Colla & Harder (2008, Biodivers Conserv 17:1379–1391) also found an apparent general decline in bumble bees in southern Ontario. These results would seem to mirror the declines and local extinctions of bumble bees that have been reported in Europe.
So what is happening in the Edmonton area? To know whether a bee is doing well or is in decline, one must first be able to put a name on it. In my experience, most entomologists can tell a bee from a fly, and many can make a good guess at family or genus, but usually only those that have specialized on bees can make a good guess at the species identity. This is true even of large, colourful, and noisy bees like bumble bees. A bumble bee proclaims its genus to anyone who cares to look, but keeps its species identity closely guarded.
So is it possible to identify the Home Bug Garden bumble bees to species – especially without killing them? Well there is a key, Laverty & Harder (1988)*, and it is worth quoting what they think: “The single most useful character for species identification is colour pattern.” (Can. Ent. 120: 966). Sounds like bumble bees and birds may have something in common. However, there is a caveat: “It should be noted that although colour pattern is usually a reliable guide to species, colour variants do occur and misidentification of some specimens is inevitable. We estimate that about 5% of specimens identified by the key will be incorrect... (p. 967).” Also, alas, the key is to the bumble bees of eastern Canada and does not include some of the most common ones in the Edmonton area. However, it does have black & white cartoon-like images of the colour patterns in the 26 species of Bombus covered in the key.
Discover Life also has a key to North American bumble bees. I’ve found this key to be a bit difficult to use and the answers I get don’t always match up to pictures (mostly really sad looking pinned specimens) or distributions (which seem to be more museum collection records than actual distributions). My getting a wrong answer may say more about me than the key, but I’m willing to share the blame. Also, the Discover Life key is clearly under construction and it seems to be improving all the time. For example, it now has Canadian Provinces as one of the characters that can be used to reduce the number of taxa.
Continuing with the Worldwide Web, perhaps the most definitive of all bumble bee keys is the British Museum of Natural History’s Paul Williams’ Lucid interactive key to queens and workers (males are not included) of the World. As with any image-rich interactive key, this requires a fast internet connection and a reasonably powerful computer to avoid giving up in frustration. The complete key contains 1070 diagrammatic images of various colour patterns, but one can select only those in the Nearctic Region – only 220 colour patterns! After that one must have some idea of the subgenus to have much hope of making progress. Subgenera should provide some grist for the Aculeate Agonistes mill and I think Bombus (Bombus) will be the first up – a nice simple, small subgenus. The colour pattern diagrams in Williams’ key and the early, black & white examples in Laverty & Harder seem pretty useful. I’m not much of an artist, but I can handle computer drawing programs and will try work up a key using cartoons and pictures to the Edmonton bumble bee fauna. Here’s a first start comparing two common black & yellow local bumble bees. Any not too caustic suggestions for improvement appreciated.
I'm sure I will be making lots of errors as I bumble through the Bombus. Corrections are always appreciated, but I hope I don't end up on Arthropoda Blog's Friday Fail!
*Laverty TM. & LD Harder. 1988. The bumble bees of eastern Canada. The Canadian Entomologist 120: 965-987.