Friday, 21 August 2009

Forever blowing bubbles

It’s the small things within the natural world that truly fascinate me, the ones that you have to get down on your hands and knees to really appreciate. As a child I would spend a greater part of the summer holidays on my hands and knees, watching insects as they went about their business. Although I have considerably less free time these days, I still find the time to watch insects, from the hoverflies perched in the early morning sun and busy cleaning their large eyes, through to the spiders that emerge from between the fence panels at dusk. These spiders are dark, almost black in colour, quite flat in shape and, for this reason, somewhat sinister in appearance.

One of the things that really fascinated me one summer many years ago was cuckoo-spit, the tight mass of bubbles secreted onto a grass blade by a tiny insect known as a frog-hopper. The name comes from their somewhat frog-like appearance; with a squat body shape and large head, coupled with a propensity for leaping, these small insects are very much like miniature frogs. The frog-hoppers, of which there are several species, belong to an order of insects known as the Hemiptera (the bugs). Included within this order are the familiar shieldbugs, water boatmen, aphids and various plant-hoppers.

The old name for the frog-hopper was ‘cuckoo-spit bug’, a reference to the frothy fluid used by the nymph for protection from desiccation. The spittle is produced by the secretion of a fluid through the anus; this is mixed with a secretion from special abdominal glands which is thought to help the spittle to maintain its coherence, even in wet weather. A special valve in the abdomen blows air into the spittle, effectively producing the bubbles. It is thought that the spittle also acts to protect the pale yellow nymph from predators and parasites but it fails to deter a Solitary wasp, called Gorytes, which drags nymphs from their bubble sanctuary to deposit them in the larval cells of its own developing brood.

While the nymphs are rather pale and unobtrusive, certain adult frog-hoppers are quite striking beasts. One of our larger species, Cercopis vulnerata, is red and black and can be found quite readily between April and August. The red and black acts as a warning colouration, suggesting to potential predators that this species is either poisonous or has an unpleasant taste. By comparison, the more familiar species, our Common Frog-Hopper, is rather understated, favouring greens and browns and relying on camouflage as a defence against predators. It is a spectacularly variable species, with many very different looking colour forms. Of course, to appreciate this you have to get your knees dirty!

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