THE PRACTICAL ENTOMOLOGIST. 



11 



Galls of the Willow and the Oak. He answers as 

 follows : — 



" I strongly incline to believe that the ' Joint- 

 Worm' must be the larva of some Gall-gnat, and 

 not, as certain authors have supposed, of a Chalcis 

 fly, for the following reasons : — 



" \st. I have had very extensive experience in 

 breeding different species of Gall-gnats (Cecido- 

 mj/ia) from the Galls of the Oak, Willow, Solidago, 

 Vernonia, Helianthus, &c. ; and I find that it is 

 very often the case, that from a gall which is fully 

 proved to be the work of a Gall-gnat, I obtain no- 

 thing but Chalcis flies. The Gall-gnats generally 

 are very difficult to breed to the Perfect Fly, and 

 often die in the pupa state, and sometimes, if the 

 gall is gathered too soon, in the larva state. On 

 the other hand, I scarcely ever fail to obtain Chal- 

 cis flies of some species or other from the galls of 

 the many different Gall-gnats that I have experi- 

 mented on. Hence, it is not at all surprising to 

 me, that both Harris and Fitch obtained nothing 

 but Chalcis flies from the 'Joint- Worm' straw. 



" 2)kI. I am acquainted with galls on the Soli- 

 doffo (Golden-rod) and the Venionia fascirulata, 

 which almost exactly resemble in their structure 

 the 'Joint- Worm' galls, being oval enlargements 

 of the stem, filled inside with a pale brown, spongy 

 substance, in which are imbedded numerous minute 

 cells. From both these galls I have bred large 

 numbers of the Lasioptera solidarjinis of Osten 

 Sacken — a minute Gall-gnat — and also large num- 

 bers of Chalcis flics, belonging both to the Eaiy- 

 toma group and to the Pleromalus group. From 

 what is to all external appearance the same gall on 

 the Golden-rod, but diifering internally in being 

 hollow with thin walls, I have also bred a small 

 moth recently described by Dr. Clemens from a 

 specimen furnished by myself* This last I rather 

 believe to be an 'Inquiline' or intruder upon the 

 Gall made by the Gall-gnat; but it is possible that it 

 is an independent gall-maker, having no connection 

 with the Gall-gnat or its gall ; and it is possible 

 again that this Gall-moth may be the author of both 

 these two kinds of Gall, and that the Gall-gnats 

 bred from them may be mere Inquilines or intru- 

 ders upon the Gall-moth. Those who desire to 

 know more on this very diflScult, curious, and in- 

 teresting subject of Inquilines or Guest-flies may 

 refer to my Paper on Willow Galls, pages 547-550, 

 {Proa. Ent. Soc. Phil, Vol. III). But be this as 

 it may, I am quite certain that the Chalcis flies 

 bred from these Golden-rod and Vernonia galls are 

 parasitic on the Gall-gnats bred therefrom ; and as 

 the galls themselves so closely resemble those of 

 the Joint- Worm, it is reasonable to suppose that 



*" Buryptychia saligneanu Clem., described in Proc. Ent. 

 Soc. Phil. V. p. 141. I had informed Dr. Clemens as to 

 ♦ the gall inhabited by this insect, but he had, as he says, 

 'unfortunately mislaid my letter," and has by mistake 

 named and described the insect as inhabiting 'a, willow 

 gall.' The name of the insect, of course, must stand, 

 however inappropriate; but the facts respecting its Na- 

 tural History may as well be corrected here. Osten Sac- 

 ken refers to this same gall Proc. d-c. I. p. 369. The Tn/- 

 peta gall which he there describes is well known to me, 

 and quite distinct from the other two." 



the Chalcis flies bred from the Joint-Worm galls 

 are also parasitic-and not true gall-makers. 



" 3rd. The Chalcis fly obtained by Dr. Harris 

 from swellings in the joints of the straw of Massa- 

 chusetts barley is a distinct species, according to 

 Dr. Fitch himself, from the Chalcis fly obtained by 

 Dr. Fitch from similar swellings in the straw of 

 New York barley, although closely allied to the 

 latter and belonging to the same genus. Now, I 

 am not aware of any recorded instance where two 

 insects, specifically distinct, produce upon the 

 SAME SPECIES OF PL.'VNT galls or swellings which 

 are indistinguishable in character. Dr. Fitch says 

 himself, that he 'had confidently expected this 

 barley straw from Central New York would give 

 him the identical insect which had infested the 

 Massachusetts barley.' Hence I infer that these 

 Chalcis flies cannot be the authors of the Joint- 

 Worm galls in barley. On the other hand, sup- 

 posing these two distinct Chalcis flies bred from 

 diseased barley straw, to be parasitic on some other 

 species of insect which produced the gall-like swell- 

 ings both in the Massachusetts and the New 

 York barley, there is nothing at all unusual in the 

 fact. For it is an every-day occurrence for the 

 same species of insect to be parasitically infested 

 by several distinct species. 



" 4th. Dr. Fitch, as quoted by Dr. Harris, (Inj. 

 Ins. p. 555,) says himself that he found, in the Joint- 

 worm galls of Barley, larvae ' with a small V-shaped 

 brown line marking the situation of the mouth.' 

 Now, this ' V-shaped brown line' is manifestly the 

 well-known ' breast-bone,' which is characteristic-of 

 the larvae of the Gall-gnat family, and found IN NO 

 OTHER LARV.^. These larvae, therefore, which 

 Dr. Fitch himself found in Joint- worm galls, must 

 neces.sarily have been the larvae of some species of 

 Gall-gnat. Why Dr. Fitch failed to recognize the 

 importance of this character, as definitively proving 

 his larvae to be those of some Gall-gnat, is explained 

 by the fact which I have elsewhere demonstrated, 

 (Proc. &c. Ill, p. 616,) viz. that he knows nothing 

 at all about it. 



" Let us recur now to the extract from the Ca- 

 nada Farmer, in the light of the above sugges- 

 tions, which I offer, not by any means as a com- 

 plete solution of the question, but as mere opinions 

 formed from the very incomplete evidence which 

 has as yet been published. Three things are tolera- 

 bly plain from this extract — 1st. That the ' two small 

 sections of wheat-straw, in which are imbedded 

 pupae' and which are located generally 'on the 

 second joitit of the straw/ are true Joint-worm 

 galls. For if the pupae had been those of the Hes- 

 sian fly, it would not have been necessary to make 

 a 'section' of the straw in order to exhibit them, 

 as the pupa of the Hessian Fly always lies, not in- 

 side the straw, but between the straw and the shank 

 of the leaf that enwraps the straw above every joint. 

 '2nd. That the ' tiny little flies' bred from the pupas 

 found in the wheat-straw from Canada are Chalcis 

 flies, probably belonging, not to the Earytoma 

 group, but to the Pteromalus group. Srd. That 

 they ' ate their way out of the sides of a certain 



