Page:VCH Surrey 1.djvu/215

From Wikisource
Jump to navigation Jump to search
This page needs to be proofread.


INSECTS viviparous brood acquire many shades of green or reddish-brown colour. This species possesses both winged and apterous males. The sycamore and the maple trees form food for Drepanosipbum platanoides and Chaitophorus aceris. The latter insect is interesting from its dimorphism. Occasionally it produces, in addition to the normal progeny, a curious toad-like form which has puzzled entomologists both as to its family and species. Under the name of Phyllophorus testudinatus it was thought to be the larva of some unknown insect. Subsequently it has proved to be an aberrant form of one of the green viviparous females of Chaitophorus aceris. These singular abortions, if they may be so called, are found slowly crawling in the condition of small yellow scales under the leaves. The body, legs and antenna? are furnished with folioles or flabellas. They are quite solitary, isolated in habit, and never develop any sexual organs, though they may persist for four or more months without leaving the leaves from which they suck the sap. They never develop wings, but they cast their integuments as delicate membranous sloughs. Though this insect has been several times described, it still forms material for the expert microscopist to work out its morphology and embryology. Aphides and galls. The obscure cause of the mimicry of the natural fruits of plants by insect agency is open to speculation and is full of interest. A good example of such is to be found in the false cones of the spruce fir, which are so remarkably similar to the true cones of that fir as to be scarcely distinguishable from them. On opening one of such cones we find the chambers to be tenanted by hundreds of the winged and oviparous females of Cbermes abietis. The delicate winged forms of these flies are often to be seen flitting above the openings of these cones on sunny days. Several galls on the oaks, made by Gynipidce, are also partially tenanted by aphides, but the species, I believe, is not well identi- fied. Erect, pedunculated galls are also found on the upper surfaces of elm leaves ; these are the work of Tetraneura ulmi. But perhaps the most remarkable gall, also on the elm, is made by Schizoneura lanuginosa. These galls are very like unripe figs, and measure as much as three inches in length. They open from the top, out of which issue thousands of the winged forms which have been bred from the apterous grubs within. Our poplars are visited by several species of aphides, each of which makes its own peculiar gall. These may be instanced by Pemphigus bursarius^ P. spirotheca and others. It is interesting to note that such galls are duly represented by structures on the native poplar trees found on the plains of Afghanistan. Some aphides are the prey of Diodontus, Coryna and Psen, all of which are minute Hymenoptera. The last-named insect carries live aphides to chambers hollowed out of the pith of the blackberry. These aphides are consumed by the larvae afterwards hatched from the ova of the Psen. Before concluding this brief account of the Homopterous Aphididae^ some remarks may be added as to the underground forms which affect ants' nests. The solicitude of these interesting Hymenoptera for the i73