82 



powdery matter, which is' well known to form gradually on the out- 

 side of the bodies of certain male Dragon-flies {Libelhda and Agrion 

 families) as they approach maturity, and also on those of several other 

 insects belonging to other Families and Orders, for instance the so- 

 called Locusts {Cicada family,) must manifestly be produced on simi- 

 lar principles. And, as we have seen in the case of the larva of the 

 common Oyster-shell Bark-louse, the powdery bloom and the cottony 

 floss, spoken of above, are met with at the very same time and in the 

 very same insect; both of them proceeding, not from the mouth nor 

 even from the tail, but from the general surface of the body. 



It is scarcely worth while, however, to argue such points as these 

 with a writer, wiio is actually so ill-informed as to assert that "every- 

 body knows that the silk spun by insects is exuded through the mouth." 

 {Dr. Packard's Paper, p. 214.) It is very true that it is so in the 

 case of caterpillars, etc.; but in the case of the Ant-lions {Mijrme- 

 leon,) the Caddice-flies {Phryganea,) the Lacewing-flies {Chrysopa,) 

 and probably of all true Neuroptera, as distinguished from the Pseudo- 

 neuroptera, everybody knows, or ought to know, that it is "exuded," 

 not from the mouth, but from the tail.* Moreover, all the spiders 

 without exception — which group of Articulate Animals Dr. Packard, 

 in common with the school to which he belongs, classifies as Insects 

 — also spin from spinnerets placed, not in their mouths, but in their 

 tails. Yet, because this writer had happened perhaps, one or twice 

 in his life, to see a caterpillar spin from its mouth, he jumps to the 

 conclusion — with the same propensity for sweeping generalizations 

 that characterizes everything that he has published — that all insects 

 without exception spin from the mouth ! ! ! 



From the enormous rate at which all Plant-lice multiply, it is 

 plain that, if there were no check upon the increase of this species, it 

 would, in a few years' time, destroy every apple-tree in South Illinois. 

 But, in all probability, there does exist one such check, at all events. 

 Eight in the middle of a little colony of these Eoot-lice I discovered 

 in November the pupa of what I am pretty sure is a Syrphite Fly; 

 and Mr. Kiley, to whom I showed the specimen, told me that he had 

 formerly found great numbers of the larva of the same species among 

 the infested roots — that he had reared it to the pupa state — but that 

 he could never succeed in breeding it to the winged state. Apparently, 

 this is the same insect, which, in the Prairie Farmer of June 15th, 

 1867, that gentleman mentions as, "having been always found by him 



*See Kirbj & Spence's introduction, letter 13th, end; letter 21st, near 

 the end; Fitch. N. Y. Rep. I. p. 79; Shinier Proc.Ent. Sv. Phil. IV. p. 210. 



