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MIX, No. 27. Whole No. 759.
Fob the Florida agriculturist. Some Economic Insects. by. P. 11. ROLFS, Forfessor of Biology, Florida Agricultural College, Lake City, Fla. ARTICLE TWO. HYMENOFTERA. Ichnemonidx.— lchneumon larva inhab its the bodies of caterpillars and other insects. The eggs are laid singly or in aggregate by ichneumon flies on the skin of the larva which the young are to inhabit. Ichneumon suturalis lives in the body of the army worm destroying many. Trogus exesorins —is a parasite on Pap ilivo Asterias a black and white butter fly. Rhyssa ( Pimpla) luncitor —is a large insect that was taken several times last year; the ovipositor is often four and a half inches long. This ovipositor is in serted into burrows of wood boring larvae and the eggs placed on its host. This unnoticed insects plays consider able havoc with some of the wood boring species. During last summer and fall specimens of the horn worm were frequently handed me all covered with small white protu berances. These white bodies were the cocoons of the Microgaster Congregata. The female is a small nearly black fly, not more than one-fith of an inch long and about the same expanse of wing. This little body darts leisurely through the air in search of its victim, which is a larva of tobacco horn worm (Miscrosila Carolina) or potato horn worm, or the to mato horn worm M. quinq item can lata. The female fly punctures the skin of her victim and lays the egg at the same time. The process is quicker done than said. The eggs hatch out in the form of footless larvae; these feed upon the inter nal fatty matter of the horn worm larva until they are full grown when they gnaw their way out through the tough skin of the horn worm and spin a small upright silky cocoon on the epidermis of their host. In from two to five weeks the par asites leave their cocoon as perfect in sects. It is needless for me to say that the host dies from the attacks of these flies. Aphidius. Sp.—There is another small four winged fly which is very common with us that is scarcely ever noticed and whose work is not appreciated; this is a small four winged fly that destroys the cabbage louse Aphis brassacsc. On warm sunny days of spring this little atom may be seen busily infecting the aphis on cabbage. One was watched last spring and in less than an hour it deposited forty-seven eggs in a colony of DeLand, Fla,, Wednesday, July 5, 1893. plant lice. Every time this parasite ap proached one of the lice the latter would wriggle about in the most frantic man ner, as if it was conscious of impending danger. The egg of the parasite is very quickly deposited, seeming to be by a mere touch. PLATE I. —2 Female, 2a Male. This fly completes its earlier growth within the host which in hitter stages becomes enormously distended. The parasite, i inmerges by pushing back a circular lid like portion of epidermis frojn the back of the host. AVc are all more or less familiar with the large angular-winged green katydid, (Microcentrum retinervis). Plate 7, 1. This is somewhat of a marvel for si/e and also for the amount of eating it does. Late in the fall these insects are of ten attracted by the light. Their notes are probably more familiar to us oven than the insect itself. Their music is simply a volume of chick-chicks thrown out suddenly without any warning. Now tl/is immense insect seems to be too large and agile to be taken in the adult state even by some of our voracious birds. However he is not to escape with out some pains, aches or diseases. The eggs are deposited in two rows on a small branch, a leaf or splinter. This fact is taken to advantage by a small four winged Hy known as the chalcid (Eupelmus Mtrabilis, Walsh —Plate I. 2, female, 2a, male.) fly. The egg of this little mite is deposited within the egg of the katydid. In this case the katydid never hatches but the chalcid fly comes out a perfect insect through a little hole in the side of the egg, as is shown in the view. The katydids hatch out by lifting up the side of the egg. I collected some eggs and placed in the breeding case and as a general rule the katydid larva immerge from the fertile egg about two weeks earlier than do the chalcids from the parasitized egg. Other entomologists have had slightly different results. Thischalcid fly israthermore than one eighth inch long. The expanse of the dusky wings is greater than the length. The male is less than the above given measurements. Moth are glossy black and nimble little fellows. Prof. Comstock recommends the col lecting of Katydids’ eggs in the fall and placing them in a box covered with a wire gauze. The gauze keeps out all an imals that might eat tin 1 eggs and allows the chalcid fly to pass out so soon as they immerge from the egg and keep the katydid nymphs in tin 1 box to starve. In i collection of a hundred and fifty seven eggs ninety-one were parasitized by chalcids against sixty-one not parasitized or 58 per cent, parasitized against 41 per cent. not. Sigalpkus curculion (Fig. 7.) accord ing to Dr. Riley destroyed over three Fio. 7. fourths of the early developed plum cur culio larva in Eastern Missouri. This little four winged fly is a very in teresting and exceedingly beneficial friend. It is widely scattered over the United States and quite a check-mate to the curculio of Florida. This little bee mite makes its busy rounds in early spring, walking over a plum the female makes close observations to find fruit with the characteristic crescent shaped gouge on it. If there is no sign of a curculio within the fruit this little atom seeks another fruit. By a movement of her anfennm she can with the most unerring precision determine $2 uer Animm, in advance