574 [December 



are by no means the first men that have been similarly deceived by 

 parasitic insects. Pome years ago one of the most celebrated of our West- 

 ern So vans announced in print, as a great scientific discovery, that he 

 had ascertained that Army-worms ( Lturnvia nnipuncta Haw.) were 

 viviparous, and that they generated in precisely the same manner as 

 Wagner supposed that Ceci(1om;/!a generated, i. e. in the larva or baby 

 state. There can be no doubt, that what he took for young Army- 

 worms issuing out of the bodies of their mothers were simply the larvae 

 of Ichneumon-flies — probably Minogastt^r militoris W^alsh or Pezoma- 

 rhus minimus Walsh, which T have myself bred from Army-worms. 

 But the mistake was the more inexcusable on his part, because if he had 

 simply looked at one of his so-called young Army-worms with his naked 

 eye, he would have seen at once, that, unlike the mother-insect, it had 

 no legs at all ; and if he had known anything at all of Lepidopterous 

 larvae, he would have known that they had just as many legs when they 

 first hatched out, as when they were full-grown. On the other hand, in 

 Wagner's case, both the so-called mother larvae and the young larvae were 

 apod, and putting the "breast-bone" out of the question, it requires 

 practiced eyes and close scrutiny to distinguish the larva of a Gall-gnat 

 from that of a Chalcidide, or from that of a (lall-fly. We saw just now 

 (p. 551) that several distinguished European naturalists had mistaken 

 the larva of a Gall-gnat that inhabits the " Rose-willow " for the larva of a 

 Gall-fly ; and I am not ashamed to confess that I myself formerly mistook 

 the dried larva of another Gall-gnat for the larva of a Gall-fly. {Proc. 

 Ent. Soc. Phil. II. p. 481-2 ) 



Like most gall-insects, and even more so than most of them, the Gall- 

 gnats are difiicult to rear in the house. The reason is obvious. When 

 the connection between the gall and its parent plant is severed, it is 

 almost impossible to devise any artificial mode of treatment, which shall 

 supply the place of the natural flow of moisture from the part of the 

 plant on which it formerly grew. Of the eight new Cecidomyidous 

 galls on the Hickory described by Osten Sacken, {Dipt. N. A. pp. 

 191 — 4) he obtained the imago from but a single one. Of the fifteen 

 new Cecidomyidous galls on the Willow which I now describe, I have 

 obtained the imago from all but nine, and one of these nine is a species 

 which does not grow near Rock Island. The method by which I achieved 

 these results was to replace the galls in the breeding-jar, whenever 



o 



