Sunday, May 15, 2011

Bumbling with Bombus: Queens & Cuckoos

 It seems to have jumped from winter to summer in the Home Bug Garden. We had three straight days of sun and +20 C temperatures in a row – unusual even in the summer. We may get three more, but the winds are so blustery that one has to hunker down to enjoy the sun. That seems to be true of the bees too: strong winds keep them low to the ground, but fortunately at this time of the year that is where most of the flowers are. The queens of the early emerging bumblebees spent the first few warm days search every nook and cranny for nest sites, but now have settled down to serious foraging.
Actually, this is most likely Bombus perplexus - perplexing indeed
 The queens of at least three species of bumble bee are braving the windy HBG at the moment, all members of the subgenus Pyrobombus. We talked about Bombus vagans perplexus, one of the black and yellow bumble bees, last year when first working out how to be sure we were looking at the apparently threatened Bombus  (Bombus) terricola. They featured in my first Bombus Cartoon. The other Pyrobombus, however, are yellow, orange, and black – and the queens of two of these are both early emerging and very similar in appearance: B. huntii and B. ternarius. I know that workers of both species foraged in the HBG last year – the workers are a bit easier to tell apart – but the only difference I can find between the queens is that in ternarius the black on the thorax extend posteriorly on the scutellum (see Bombus Cartoon Mark II below).
 As we all know, I’m a bit camera-challenged and the wind hasn’t helped a bit, but I’ll offer a couple of blurry Bombus ternarius pictures in support of the identification. At least one smaller queen with yellow followed by three abdominal stripes of orange also passed through – most likely Bombus centralis – but the wind carried her away faster than I could start up my point-and-shoot.
 Lots of smaller hairy bees have also been out and I believe they belong to the genus Andrena – a complex group with lots of species. Along with the Bombus queens, these bees clearly liked foraging at Coltsfoot (Petasites palmatus) and Siberian Squill (Scilla sibirica 'Spring Beauty'), and the Bombus also went after the Striped-Squill (Puschkinia scilloides 'libanotica') voraciously. Tulips, except Tulipa tarda, seem of little interest to the bees and the large Dutch crocus accounted for all but one or two of the crocus visits that I saw (and the smaller crocus out numbered the Dutch crocus by about 20:1). 
 So, I guess I’ll just have to consider the hybrid tulips, daffodils, and smaller crocuses for me and the rest for the bees. However, there was one bee at the squill and coltsfoot that I’m not so sure I was happy to see, although it represented a new HBG record – a species of Nomada
 These wasp-like bees are cuckoos – the females enter the nests of other bees, lay an egg, and their grub eats up all the host bee’s provisions (this is called cleptoparasitism – same root as in kleptomania). I suspect it is the Andrena that will be robbed (blurry below, better one here from a previous May).

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