. Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges . pointed out, since the insects are usually small in size ; indeed, it is a matter of little importance to the farmer, because in any case he can look upon these gall-wasps with indifference, and without much fear of possible injury to himself. There is a very large series of parasitic Hymenoptera, and it contains a number of families, nearly all the species of which are beneficial. To the practised eye a doubt rarely exists as to whether an insect is parasitic o
. Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges . pointed out, since the insects are usually small in size ; indeed, it is a matter of little importance to the farmer, because in any case he can look upon these gall-wasps with indifference, and without much fear of possible injury to himself. There is a very large series of parasitic Hymenoptera, and it contains a number of families, nearly all the species of which are beneficial. To the practised eye a doubt rarely exists as to whether an insect is parasitic or not ; but that the student may be able to decide this matter for himself if he chooses, it may be pointed out that the trochanter, the little segment between the coxa and femur of the leg, is rather peculiarly de- veloped here. It is normally composed of one joint only in all the bees, wasps, and ants, whatever their size or appearance, but it is two-jointed in all the parasites. ""' two-jointed trochanter , ., of parasitic Hvmenoplera: This character can be easily seen on large ^^ normal structure. specimens with or without a lens, but on minute species it becomes more difficult ; and, after all, in most cases the farmer is justified in assuming that most of the minute wasp-like creatures that he notices are parasites and beneficial. One feature characteristic of a great number of species is an external ovipositor, or egg-laying tube, and this may vary from a scarcely visible projection to an enormously developed hair- like appendage five to six or even more inches in length. There may be frequently seen on the trunks of various trees a quite large ichneumon, a Thalcssa, yellow or black in color ac- cording to the species, which has its long, bristle-like ovipositor forced deep into the wood, and so firmly fixed, occasionally, that it is unable to wathdraw it, and perishes miserably. Wherever this occurs the trees will be found infested by borers, and all but unive
Size: 2194px × 2278px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphila, bookyear1896
