HEMIPTERA—HOMOPTKRA— APHIDES, 243 



forms are figui-ed, and besides these another winged plant louse of a diminu- 

 tive size, showing the characteristic venation of the group. In the Ter- 

 tiary rocks a considerable number of species have been found; most of these 

 have been referred to Aphis (twelve species) and Lachnus (eight), and so 

 belong, like the bulk of living species, to the subfamily Aphidinas ; but 

 the Pemphiginse are represented by a Pemphigus fi'om Oeningen and the 

 Schizoneurinaj by a Schizoneura from amber. Besides occurring in these 

 localities they have also been found at Radoboj, Aix, and Ain, in Europe, 

 and we can now add several localities in our own country. That they are 

 not scarce in amber is shown by Menge's collection, which in 1856 included 

 fifty-six specimens. But these are few compared with the number from 

 Florissant, where more than one hundred specimens have been found, about 

 seventy of them determinable, though in the other American localities — 

 Green River and Quesnel, Bi-itish Columbia — only two or three specimens 

 have occurred. Indeed, by the present publication the number of known 

 fossil species is doubled. 



There are some remarkable features about the Florissant forms. The 

 mass of them belong, as is the case with those from the European Tertiary 

 rocks, to the Aphidinse proper. But both here and in the Schizoneurinse, to 

 which the remainder appertain, we are met by two remarkable facts, one 

 that the variation in the neuration of the wings is very much greater than 

 occurs among the genera of living Aphidinae and Schizoneurinse, and greater 

 also than occurs in the known Tertiary forms of Europe, requiring the 

 establishment of a large number of genera to represent this variation ; and, 

 second, that at the same time there is one feature of their neuration in 

 which, without an exception, they uniformly agree, and differ not only 

 from the modern types but from the European Tertiary insects. This fea- 

 ture is the great length and slenderness of the stigmatic cell, due to the 

 removal of the base of the stigmatic vein to the middle (or to before the 

 middle, sometimes even to the base) of the long and slender stigma, and its 

 slight curvature ; it is a fact of particular interest in this connection that 

 in the only wing we know from the Secondary rocks precisely this feature 

 occurs, as illustrated in Brodie's work (see PI. 4, Fig. 3). So, too, the cubital 

 space is largely coriaceous, so that the postcostal vein may be considered 

 as exceedingly broad and merging eventually, without the intervening lack 

 of opacity, into the stigma proper. As a general rule the wings are also 

 very long and narrow and the legs exceedingly long. In all these charac- 



