46 



THE PRACTICAL ENTOMOLOGIST. 



ANSWEKS TO CORRESPONDENTS. 



M. S. Hill, Ohio. — The numerous white egg-like bodies 

 about one-eighth of an inch long, attached to the alco- 

 holic epecimen of the common Tomato-worm which you 

 transmit, are not eggs but the cocoons of small Ichncu- 

 mon-flics, belonging to the genus Microqasicr. Their his- 

 tory is briefly this. The molher-fly pilnctures the body 

 of the young Tomato-worm and deposits therein a num- 

 ber of eggs. These eggs hatch out into litlle footless mag- 

 gots, and feed on the internal substance of the larva till 

 they have attained their full growth, when they bore 

 their way out and spin, each one for itself, a sillten co- 

 coon on the external surface of the now half-killed larva 

 In three or four weeks afterwards the perfect ichneumon- 

 fly emerges from the cocoon, couples, and repeats the 

 same operation in other larvK. In Harris's Injurious In- 

 sects (p. 327) you will find a wood-cut of anotlaer kind of 

 larva which has been attacked in the same manner, and 

 of the perfect fly that is parasitic on it; and I have a spe- 

 cimen in my collection that is so completely covered by the 

 parasitic cocoons, that no part of it can be seen but the 

 head and the anal horn. It is a very common thing also 

 to see different kinds of "span-worms" walking about 

 with four or five of these parasitic cocoons attached to 

 their bodies. In some of the specimens you send, the 

 Microgaster is in the pupa state, and of a blackish color- 

 in the rest it is still in the larva state and of a whitish 

 color. If you had not immersed them in alcohol, they 

 would have almost all changed in a few weeks into small, 

 black flies. 



The mass of similar egg-like bodies, which you found 

 attached to a stem of grass, is nothing but the empty 

 cocoons of a Microgaster, which had deserted the body 

 of the infested larva before spinning up. In the Trans- 

 actions of the Illinois State Agricultural Society I have 

 described and figured a species which behaves in this 

 manner towards the common Arrny-worm. (Vol IV p 

 367 Microgaster mililaris.) Certain species, before spin- 

 ning their cocoons, unite all together in first spinning a 

 mass of cottony, flossy matter by way of external protec- 

 tion; and this is the case with the Parasite of the Army- 

 worm that has just been referred to. They are very com- 

 mon and abundant insects, and are of infinite service by 

 checking the undue multiplication of plant-feeding larvae. 



B. D. W. 



Thos. E. Payne, Iowa— You send a thin, gauzy cocoon 

 about an inch long, with a large mass of whiteeggs attached 

 to it externally, and glued together by a white foam-like 

 substance. You found it, you say, fastened to the dead 

 leaf of a pear-tree, and similar ones on apple-trees It is 

 the cocoon and eggs of Orgi/ia leurosiigma, a. very common 

 moth which lays its eggs, not only on fruit-trees, but on 

 a great variety of forest-trees. The female moth has no- 

 thing but the merest rudiments of wings— as is also the 

 case with the notorious Canker-worm— and always lays 

 her eggs on the cocoon in which she emerged from the 

 pupa state. The male moth has full-sized wings, and is 

 therefore able to fly round in search of the female The 

 larva is one of the most beautiful objects in nature and 

 baa a coral-red head and long pencils of black tufted 

 hairs before and behind. You will find colored figures of 

 the larva, of both sexes of the moth, and of the cocoon 

 and eggs, in Harris's Inj. Ins., PI. 7, fig. 1—5. b. d. w. 



0. Cook, Mass.— What you take for a "package of eggs " 

 one of which packages happened to be attached to the 

 eggs that produce the common apple-tree caterpillar, are 

 not eggs but cocoons. From a very similar mass of co 

 coons we have bred a rather rare species of Microaaster 

 and yours undoubtedly belong either to that or some 

 other species of that genus, which is a very extensive one 

 and comprises very numerous groups. They are all pa- 

 rasitic insects, belonging to a sub-division of the great 

 family of /cA/ieumon-flies, called Braron ida: ; and instead 

 of destroying them, you should cherish them as the very 

 apple of your eye. But for the difiereut kinds of Ic/meu- 

 mon-iiies, leaf-eating insects would soon increase to such 

 a prodigious amount, as to devour every green thing on 

 the face of the earth. ^ 



As to the "little cocoons which you find in Urge num- 

 bers on your apple-trees," eitlier you failed to send anv, 

 or they have by some accident been lost or mislaid. 

 Ihere is nothing to be seen now in your package, but two 

 of the well-known masseB of eggs that produce the com- 



mon caterpillar and the mass of cocoons above spoken 



i /.u"^® ^'""^ """■"' ''"'* ""> ^'" endeavor to tell you 



what they are As you say they occur in large numbers. 



send plenty of specimens. * muers, 



Geo. E. Brackott, Maine.— The common "caterpillar" 

 of the apide tree occurs on several forest-trees, as well as 

 the cultivated apple and cherry tree and the wild cherry, 

 plum and crab. We have frequently noticed them on 

 willows, aiid Dr. Fitch found them on witch hazel and 

 poplar. You say that you found a belt of the egg on a 

 twig of yellow birch. When, as in 1865, these catlpiUara 

 are so exorbitantly numerous as to strip the trees which 

 they usually inhabit, they then disperse and seem to feed 

 almost indiscrimately upon any tree that comes handy 

 to them. ^ 



You are quite right in regard to the specimen sent. It 

 IS the pupa of the common "caterpillar" of the apple- 

 r^r!, n 1^1" u P-'"-='«!t'<=alIy infested by two or three 

 lachma-ates, that have constructed their cocoons (pupa- 

 r.a) inside its body. Tachina is a family of two- winged 

 Flies {I),ptera) many species of which closely resemble 

 House-flies and Flesh-flies, but may be distinguished by 

 the bristle of their antenme being smooth and not fea- 

 tnered. Iheir cocoons (j.uparia) are not spun out of silk, 

 as are those of the Ichneumon-mea, but are composed of 

 the dried-up and shrunken skin of the larva, and are 

 generally ot a shining mahogany color with the joints in 

 the body 0/ the larva still plainly perceptible. The larvae 

 found inside one of these Tachina cocoons are, as you 

 rightly suppose, parasites upon the parasite, and many 

 similar cases have been recorded by authors. As they 

 have spun cocoons, they probably belong to the Procto- 

 trupes and not to the Chalcis family; but it is impossible, 

 without rearing the perfect insect, to say to what speciea 

 or even to what genus they appertain, and we may make 

 tbe same observation with regard to the Tachina fly 



Authors have generally supposed thatwhile the primary 

 parasitic larva is still feeding inside the body of its vietini. 

 It IS punctured by the secondary parasitic fly, and has one 

 or more eggs deposited in its own body, which afterwards 

 hatch out and gradually destroy it. Certain facts with 

 which we have been aoqainted seem to be explainable 

 on yon that hypothesis; but Dr. Fitch infers that it is 

 only after the primary parasite has issued from the body 

 of its victim that it is punctured by the secondary para- 

 site. Very possibly this may be the case sometimes; and 

 sometimes the former supposition may be the correct one. 

 Wm. A. Woodward, N. Y.— The twig from a peach-tree 

 which you send contains the eggs of some Homopterous 

 tnsecl, perhaps a Cicada, or, as it is commonly called, a 

 Jjoeust. Without breeding the insect from the egg it 

 18 impossible to speak with more precision, as the eggs of 

 the whole group resemble one another very ciSsely. 

 Iheir size is the only reason we have for supposing them 

 to be the eggs of some species or other of Cicada They 

 are not the eggs of the "17-year" Cicada, because those 

 are said to be deposited in a double row, and yours are in 

 a single row. 



— • » 



B@" The various sorts of graia are, from the mo- 

 ment when as seed they are committed to the earth, 

 till they have attained their perfect maturity, ex- 

 posed to the attacks of various sorts of insects. The 

 farmer, who is entitled to expect a plentiful crop 

 from the soil and favourable weather, often finds his 

 hopes disappointed, without being able to guess at 

 the cause. An insect, which escapes his notice 

 from its minute size, as well as from the difficulty 

 of finding out its abode, is at work destroying the 

 fruit of his labours. The agriculturist, who is un- 

 acquainted with the economy of insects, seeks in 

 vain for the author of this destruction, and not un- 

 frequcntly attributes it to creatures which, in reality, 

 are his benefactors. Thus it happens that many 

 buds are scared away from our fields, whose prin- 

 cipal nourishmcut consists in insects; and that 

 moles, which live entirely on the larvte of insects 

 lying in the ground, are hunted out and destroyed. 

 —rKSllar. ' 



