Posted: Wednesday 30 March 2011
by Richard Jones
The south-facing fence of our garden is covered all over with ivy, and the leaves are prime basking territory for all manner of insects.
The south-facing fence of our garden is covered all over with ivy, and the leaves are prime basking territory for all manner of insects. This last week, the solitary bees have started to reappear in droves. There are very many species all looking a bit like slimmer, racier relatives of the honeybee, and although they are notoriously difficult to identify, I've seen several species already. There are many males of the tawny mining bee, Andrena fulva, which is smaller, slighter and blacker than the rusty-red females. And there were several specimens of the distinctive large black and ashy white Andrena cineraria.
Lots of the bumblebee-like Anthophora plumipes have been darting about. The all-black females are often pursued by a posse of black and brown males. And one of the large spotted Melecta species was resting, just out of clear sight, at the very top of the hedge. They seem to favour the higher leaves, leaving the lower ones for hoverflies and blow-flies. I’m wondering if there is a biological reason for this.
Honeybees, bumblebees and social wasps all congregate around prominent branches or treetops when they mate. Males gather together at these vantage points and mark them with a scent which then attracts females. These 'social' insects go through this behaviour in autumn, and only the fertilised queens (females) survive through winter. In the 'solitary' species, the bees develop in their mainly subterranean nests, and although the grubs may finish feeding on the stored stocks of pollen and nectar cake laid in by their mother, and have developed into adults, they delay final emergence until spring. It is then the males that emerge first, often several days before females from the same nest. They then wait about until the females appear. I'm left wondering if my ivy hedge is a solitary bee lecking point.
As I patrol up and down trying to get a closer look at the various bees, I come across some other bundles of animated fluff. Two bee-flies, Bombylius major, are also sunning themselves here. They are smaller and tubbier than the bees, and have a distinct long straight pointed proboscis for sipping nectar while hovering in mid air. It's no coincidence that they are here too. When the bees start to dig their nest burrows in the loose soil, the bee-flies will be on hand to take advantage. They are brood parasites. With a characteristic bobbing flight, they flick their tiny bouncing-bomb eggs into the bee burrows. The bee-fly larvae quickly hatch, then eat pollen, nectar and host bee grubs.
The ivy is not just a sun-washed bee-dating market, it is a whole furry ecosystem.
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