THE AMERICAN ENTOMOLOGIST. 



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two small specimens of this g^all fri'owing upon 

 the cane of the wild Frost Grape in Illinois ; and 

 we were presented with two very large speci- 

 mens by Mr. Mills of Hock Island, 111., which 

 had grown wpon a Frost Grape (jlaiited in his 

 dooryard, from one of which the annexed draw- 

 ing is copied (Fig. 80). The wliole mass of 

 galls springs ftom a common Lontie tt the point 

 [tig % 1 



'J 



Color — Green. 



where a bud would normally be, and is evi- 

 dently a mere deformation of a bud. Occasion- 

 ally an iiudeformed leaf with its peduncle still 

 entire puts forth from the common centre, some- 

 times bearing a couple of galls at the junction 

 of the peduncle with the leaf. j;achgall is one- 

 celled, the cell being about a quarter of an inch 

 long and one-fourth as wide as long, and con- 

 taining a single larva. (Sec Fig. 86,6). Tlie 

 larva closely resembles tliat of the Grape-vine 

 Apple-gall, and is therefore no doubt that of 

 some Gall-gnat. Large siz.ed specimens of this 

 gall bear a general resemblance to a bunch of 

 filbert or hazel nuts, as they grow on the bush: 

 hence the name that we have given it. Fnller 

 details will be found in the foot-note.* 



•Gall ViTis CoKYLOiDES, N. Sp, On the oiine of Vilh 

 cordi/oUa —Xroaadiah mass, li to 2i inclii>'- in iliRou'tor, 

 of from 10 to 50 opaque, woolv-pubescent, fu^itonn, ur 

 sometimes flattish-oval, Kreen galls, eai^h IVom O.w to O.Tri 

 inch long, the whole springing Irom the point where niivinal- 

 !y a hud 'would be located, (ienerally it is only the terminal 

 }" of each gall that is pubescent, the'ba^al | being smooth . 

 The interior of each gall is fleshv, juicy and subacid, with a 

 single longitudinally central cell o.'2."> inch long and 0.06 inch 

 in diameter. 



Larva.— Orange-yellow, with the disk of the dorsum 

 paler. Breast-bone as in the preceding. Length 0.11- 

 0.14 inch. 



Galls made by Plant-lice {Aphides). 

 Tlie galls hitherto referred to have been those 

 w liich are formed by the mother in.sect depositing 

 one or more eggs in or on the tissues of the plant 

 which she infests. Those to be now treated of 

 belong to the second or exceptional group, 

 which are formed by a young larva stationing 

 itself externally upon some particular part of the 

 infested plant, usually the leaf, and causing that 

 part to bulge out into a sack, which finally closes 

 at its mouth and shuts up the larva in a kind of 

 prison of its own m.iking. We see the abortive 

 beginnings of this process in the case of many 

 species of I'lant-Iice and of Mites; for example 

 the common Currant Plaut-louse {Aphis ribis) , 

 and sundry Mites that attack the leaves of o.aks. 

 For here, although the leaf bulges out into a ca- 

 pacious hollow inhabited by the leaf-feeders, yet 

 the hollow never, under any circumstances, 

 closes at its mouth into a true sack-like gall. 



[Kig-. ST.) 



The V'.VGAiiOXD Gall (Populi vayabunda, 

 Walsh), Fig. 87. — This gall occurs in particular 

 years in prodigious abundance on the tips of the 

 twigs of certain Cottonwoods, but in other 

 years there is not one to be found in the same 

 district. The old blackened galls, however, 

 hang on to the twigs for several seasons, giving 

 the tree a singular appearance when the leaves 

 are oft" in the winter time. The fly was discov- 

 ered and described before it was known to in- 

 habit any gall, and received its name from the 

 habit that it has of wandering to very great dis- 

 tances in its native forests.* It may be called 

 the Vagabond Plant-louse (I'emphiffus vaga- 

 bundus, AVnlsh), and is represented in Fig. 88. 



•.See Proc. Enl. Soc, Phil., I, p. SX. where the fly i.s de- 

 scribed, and II, p. 4(j2, where the gall is described. As to 

 the generic determination of this Plant-louse, see Ibid \1., 

 p. 280, note. 



