Economic entomology for the farmer and fruit-grower : and for use as a text-book in agricultural schools and colleges . rge in due time dozens of Ptero-nialus piiparum, a greenish-bronze Chalcidid, instead of thecommon white cabbage butterfly. Though these insects arc minute, being scarcely one-eighth ofan inch in length, vet they are giants compared with otherswhich live in scales and even in the eggs of other insects. Veryfrequently such Chalcidids are bred from galls, and they are hereeither parasitic upon the actual gal1-ni;iker, or they may live inthe abnormal tissue j)roduced by the Cyni
Economic entomology for the farmer and fruit-grower : and for use as a text-book in agricultural schools and colleges . rge in due time dozens of Ptero-nialus piiparum, a greenish-bronze Chalcidid, instead of thecommon white cabbage butterfly. Though these insects arc minute, being scarcely one-eighth ofan inch in length, vet they are giants compared with otherswhich live in scales and even in the eggs of other insects. Veryfrequently such Chalcidids are bred from galls, and they are hereeither parasitic upon the actual gal1-ni;iker, or they may live inthe abnormal tissue j)roduced by the Cynipid larvae. We find 25 386 AN ECONOMIC ENTOMOLOGY. the little fellows everywhere, infesting almost all kinds of insects,and undoubtedly they do much to prevent the increase of injuri-ous species. Especially is this true of those ovipositing in eggsof other Ibrms, for they are then nipped in the bud, so tospeak. Their work in the destruction of scale insects is also ofgreat importance, and frequently we find on a scale-infested treea large proportion with little round holes, showing where a para- FiG. 445. Fig. 444. Trickogranima pretiosa, a parasite in insect eggs ; a(lot may represent natural size. Female Isosoma oviposit-ing in stem of wheat. site has emerged. It is a pity that in a family so generally usefulwe should find, exceptionally, some injurious species ; but thereis no doubt that members of the genus Isosoma lay their eggs inthe stems of grasses, including wheat, and the larvae, working asthey do in the joints, have received the name stem hardens where the larva punctures it, and this inter-feres with the nourishment of the plant above that point, les-sening or entirely preventing the formation or maturing of thegrain. There is but a single annual brood of these insects, andthe winter is passed in the straw, from which the adults emergein spring. In localities where this insect is sufficiently abundantto make it necessary to use remedial measures, the
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectinsectp, bookyear1906
