Saturday, May 2, 2015

Insects are Harsh: Large Bee-Fly - Bombylius major - Grand bombyle

It was remarkably nice out today, so I decided to head out to the mountain with my camera to enjoy the weather and to see if the insects had started to wake up. They certainly have! In the various places where the spring ephemerals were in bloom, virtually no flower sat untouched for more than a few moments while I was observing. The pollinators are out in full force. I didn't see any Bombus spp or Apis spp, though. Just a variety of solitary bees, some Syrphid flies, a single Pieris rapae (cabbage white butterfly), and of course a large bee-fly.

The large bee-fly is a member of the Bombyliidae (bee flies) family, a group of bee flies (Order Diptera). Though they are flies, they are bee mimics. Mimicry generally is selected for when the mimicry is of a species to which predators are either indifferent or avoidant.

Unfortunately, the Bombylius major individual I spotted today pollinating T. farfara in the Notre-Dame-des-Neiges cemetery refused to hold still. It's quite tricky to locate an individual, pursue it until it lands, orient the camera in close without scaring the insect away, focus correctly, then take the photo. So, I have only the one photo, which is not great.

B. major pollinating T. farfara
In any case, B. major is a great example of the harshness of nature. B. major is a parasitoid of ground-nesting insects [1] (particularly solitary bees of the genus Andrena) [2]. The major difference between a parasitoid and a parasite is the outcome for the host. A parasite may reduce the fitness and competitiveness of the host, but doesn't assure its death or inability to reproduce; a parasitoid will eventually either sterilize or kill its host.

So B. major's basic method is to seek out ground nests (eg those of Andrena spp.) and deposit their eggs or larvae nearby so that they can crawl into the nest. The larvae then will attach themselves to the Andrena young, feed off them, and eventually kill them. Failing this, B. major will deposit the larvae on flowers that Andrena queens might visit, so that the larvae might be carried off into the nests. [3]

I witnessed a huge number of solitary bees visiting T. farfara today, so this B. major individual will have no shortage of potential hosts for its young.


Bonus photo of S. siberica, just to have something pretty to look at in this post:

Scilla siberica

No comments:

Post a Comment