Posted: Wednesday 19 December 2012
by Richard Jones
No, it’s not quite time for hibernation yet. Just a bit of sun and all kinds of intriguing insects are out again, the most noticeable today being the froghoppers.
No, it’s not quite time for hibernation yet. Just a bit of sun in the garden and all kinds of intriguing insects are out again. I thought maybe I’d seen the last of this year’s hoverflies, but a drowsy marmalade fly, Episyrphus balteatus, is twitching its wings on an ivy leaf. I don’t think anyone can remember why this hoverfly has such a daft common name - it’s one of the reasons I stick with my entomological snobbery and insist on scientific names, even for the most familiar of beasts. There are several large bluebottle blowflies, Calliphora species, sunning themselves on the fence between loud lazy bouts of buzzing flight.
But the most noticeable insects today are the froghoppers, Philaenus spumarius. This is the common spittle bug, whose soft pallid nymphs make the white frothy gobs of cuckoo spit as they feed by sucking plant sap. There are dozens of them. And not only are they hopping about on the sunny foliage, they’re busy having sex too. Perhaps this is a bit ambitious, given that they’re unlikely to have time to get another generation through to adulthood before the real winter arrives.
Of course, they aren’t really consciously trying to do that. These are creatures of instinct, and they’re just reacting to one of the standard environmental stimuli - ambient temperature. But even in simple creatures, like insects, there is no on/off switch for hibernation, or mating, or indeed any behaviour. There is a spectrum or gradient, at some point along which the behaviour will be initiated. If the stimulus continues for long enough, the behaviour will be completed.
If there were a fixed temperature at which hibernation started, the poor beasts would be switching in and out of it like yo-yos, with every daily setting and rising of the sun. There is a long period of preparation, as each day is slightly cooler than the last. It just so happens that the sudden sunshine has temporarily reversed the gradual physiological transition from active, mobile, lively creature to quiet, hidden, secret, torpid hibernator.
True winter will come, but not yet, and not quite as suddenly as portrayed by Hollywood or on faux-Victorian Christmas cards.