Page:VCH Essex 1.djvu/145

 INSECTS with their life history are so intensely interesting that they are well worthy of far greater attention than they have hitherto received. It has been already stated that the females greatly outnumber the males, but in many cases the males are quite unknown and in some species only females are believed to be produced. Parthenogenesis is extremely common among them, and though in some instances ova deposited by virgin females have produced males, as a rule such ova produce only females, and it has been abundantly proved that these possess the faculty of reproducing their like without any male assistance for an indefinite number of generations. Among the more noteworthy species found in the county, attention may be drawn to those of the very handsome genera Lyda, Abia and Arge , which are well represented. Three species of Do/erus (D. rugu/osus, D. fumosus and D. gibbosus) are as yet only known as British from examples captured near Colchester, where Loderus palmatus is occasionally found. The rare Macrophya rufipes is also worthy of mention, and Allantus jlavipes is from a collector's point of view a good insect, as it is not often obtained in Britain and is scarce elsewhere. Several specimens were found on charlock flowers near Langham Lodge Wood many years ago, but none have occurred recently. The male of Strongylogaster cingu- latus is accounted a rarity though the female is abundant, but one day in the spring of 1899, in Donyland Wood, several males were captured before any females had been seen, which is contrary to Mr. Cameron's experience, as he states that though he has bred hundreds of females he only succeeded in getting one male, which curiously enough appeared some days after all the females of the same batch had emerged. As two of his virgin females produced fertile eggs he concludes that partheno- genesis plays a constant r61e with this species. Allantus zona is another scarce species which has occurred at St. Osyth. The Gallflies (Cynipida) form those abnormal growths upon trees and plants of which the oakapple, the marble and woody galls of the oak, and the moss-like Bedeguar gall of the rose are familiar and conspicuous examples, but all gall-producing insects are not Hymenopterous, as many of them belong to other orders, such as the Gall-gnats (Cecidomyida) among the Diptera and certain of the Aphides and beetles. The facts and problems connected with the reproduction of the Cynipidce are even more interesting and complicated than in the case of the Tenthredinida, and though it is impossible to go fully into them here, it may be briefly stated that some insects which were formerly believed to be distinct are now known to be different forms of the same species, which inhabit totally dissimilar galls and appear at different times of the year, the earlier brood consisting of both males and females and the later brood of females only, which lay fertile eggs and produce the bisexual brood of the following season. But besides this alternation of generations, there are other species which are well known to be single brooded and which consist of females only, for though they have been bred by hundreds of thousands by different investigators, all endeavours to discover the males have been 107