408 [NoVEMliER 



to its full completiou, because it can only be in very rare cases indeed, 

 that intercrossing with the other Phytophagic Varieties of the same 

 species can be avoided, and the Law of Assimilation prevented from 

 coming into play. 



If these views be correct, we might expect to find Phytophagic Va- 

 rieties and Phytophagic Species most abundant in those vegetable-feed- 

 ing genera, where the imago flies but little, or flies very weakly, or has 

 no wings at all, and where consequently intercrossing does not so rea- 

 dily take place. Such genera are Gi/nlps and its allies in Hymenop- 

 tera, Cccidomi/ia in Diptera, Apliis and its allies and Coccus and its 

 allies in Homoptera, Tini/is in Heteroptera, and Diapheiomera in Or- 

 thoptera, though this kst makes up perhaps to a certain extent for its 

 want of wings by its great powers of walking. All authors have re- 

 marked upon the minute shades of diff'erence that distinguish the spe- 

 cies of the four first genera and their allies, and upon their being fre- 

 quently restricted to certain species of plants. I have myself recently 

 observed, that an apparently undescribed species of Tingis, which oc- 

 curs profusely on the basswood and the false indigo (amorpha fruticosa), 

 when it occurs on the latter plant is always distinguished from the bass- 

 inhabiting type by the carinate basal cell of the elytra terminating be- 

 hind nearly in a rectangle, instead of an angle of about 60° or 80'^, 



and is probably, therefore, divisable into two Phytophagic species.* 

 » 



*I have before referred to this Tingis. [Proc. Ent. Soc. Phil. I. p. 295,) though 

 I had not then noticed the nice structural distinc'.iou between the two forms 

 inhabiting respectively the bass and false indigo. Some specimens found on 

 the wild cherry were identical with the bass-inhabiting form, and as they oc- 

 curred on a tree not far removed from several basswoods. might j^ossibly have 

 flown there from them. The false indigos on which the other form occurred had 

 no trees growing within a furlong of them. Believing the two forms to be dis- 

 tinct Phytophagic Species, and that both are undescribed, I annex descriptions : 



Tingis tiliae n. sp. Pale brownish yellow. iJeati more or less blackish. Eyes 

 black. Autennse nearly as long as the body, finely pilose when held up to the 

 light, the terminal joint thickened and blackish, joints 1 and t each twice as 

 long as joint 2, and joint 3 about four times as lon^ as joint i. Prothora.r late- 

 rally dilated in a thin, semitransparent plate directed ujjwards and outwards, 

 and filled with small suborbicular cells like those of the elytra. This plate 

 commences from nothing at the origin of the elj^tra, and thence gradually widens 

 to one-fifth the width of the entire prothorax at the lateral middle, where it 

 curves inwards rather suddenly and is prolonged forwards in a very gentle con- 



