OF WASHINGTON, VOLUME XVII, nu:, \l) 



ation, in which case we have two very different forms, sisters or 

 at least cousins, whose purpose in the economy of the insect 

 may be as widely separated as their forms. Like the stem- 

 mother these forms are parthenogenetic and like them, again, 

 they may be viviparous or oviparous. This group may com- 

 prise from one to twenty or more generations. Finally there 

 occur the sexes; females mate with males and produce eggs. 



The matter is further complicated by the fabt that there are 

 countless variations of these general types, usually evolved in 

 conjunction with some peculiar mode of life in a particular species, 

 or group of species, or occurring in order to aid certain species 

 to pass through adverse climatic conditions occurring during 

 the year's cycle; for example, certain subterranean and gall 

 inhabiting forms, and the flabellate form of Chaitophorus tesluili- 

 natus Thornton, in which stage the insect passes through the 

 warmer period. However, these different forms may be further 

 combined into two groups, alate and apterous if the general 

 form be the standard, or parthenogenetic and sexual when classi- 

 fied according to the mode of reproduction. To confuse matters 

 still further, several observers have recorded, during the past 

 thirty-five or forty years, adult forms which hold an intermediate 

 position between the two groups, whichever classification be used. 



What appears to be the earliest record of such an intermediate 

 form is that made by Fatio (1876) in Ph. vastatrix. He speaks 

 of a "pupa" which deposited (sessuali) eggs on the roots. This 

 pupa was undoubtedly an intermediate. Maxitz (1893) describes 

 two anomalous "pupa)" in this species, which in general re- 

 sembled true pupae, but had only foldings of the skin to represent 

 wing pads. He believed these to be fully matured individuals, 

 not pupa? arrested in development but intermediates between 

 the apterous root form and the pupa. In this same specie- 

 Stauffacher in 1907 noted observations on "pupa?" which pos- 

 sessed the "corsaletto" found usually only in the alate insects. 

 In 1908 and again in 1912, Grassi and Foa recorded observa- 

 tions on intermediates, accompanied by quite detailed descrip- 

 tions of several specimens, or groups of specimens. They stun 

 that their observed forms can be arranged in a series from apter- 

 ous to alate. All of these intermediates with one exception, 

 were virginoparae, the one exception being a sexupara. 



In other Phylloxera Dreyfus (1889) described intermediates 

 (calling them apterous) in coccinea Drey, punctata Licht., and rut /In 

 Drey. He states that he observed apterous sexupara 1 with eye- 

 composed as in the alate, or better as in their pupa* and with all 

 three ocelli present. He also observed in rnt-il. "pupa*" with 

 the "corsaletto" later found by Stauffacher in raxtatr/.r, as already 

 recorded. 



