OF WASHINGTON. 115 



capable of extended individual life prolongation there is good 

 evidence, and this is particularly the case with those which are 

 partially parasitic or infest other animals. Thus the common 

 Acanthia lectularia will survive in almost any state for more 

 than a year under conditions which retard development. 



In the Homopterous division we find great variation in the life 

 of individuals. In the Membracidas and the other families which 

 are, when once out of the egg, active throughout life, the winter 

 is passed in the egg state rarely in the adolescent states. The 

 same is essentially true of the Aleurodidae, though there are a 

 number of exceptions. In the Psyllidae the winter is more often 

 passed in the adult state, the exceptions being few. In the 

 Aphididag, where alternation of generation and parthenogenesis 

 complicate the question, the adults, nevertheless, are, as a rule, 

 ephemeral. The great majority of the species hibernate in the 

 egg state. The gall-making species are, in the active states, 

 longest lived in the stem-mother, which hatches from the winter 

 egg and founds the gall in spring, while the true-sexed individuals 

 are born for no other purpose than the production of the impreg 

 nated egg, are short-lived and are often incapable of feeding. The 

 great variation in this respect which may obtain, however, is well 

 exemplified in the Phylloxerinae, in which, of the many species 

 which occur in America, especially upon our hickories, we have 

 every variation from those which produce practically but one 

 generation annually, and which thus live individually for nearly 

 a year, to those species which are reproduced agamically through 

 out the growing season and produce the sexed individuals and 

 the winter-egg only as winter approaches. The number of these 

 agamic generations varies according to the species. In the Coc- 

 cidaa, also, the majority of the species hibernate in the egg state, 

 but, as I have shown in recent notes before the Society, there is 

 the greatest irregularity, and the dormant period may be passed 

 in all stages of growth and in a variable manner in the same 

 species. (Proc. Ent. Soc., Washn., in, p. 65.) 



On the whole, therefore, it may be stated that the Hemiptera 

 generally close the active individual life within a single year, and 

 that the chief exceptions are to be found in the Heteropterous 

 division among the species which have become household tenants 

 with man, or among those which have a hypogean larval life. 

 They show every variation, also, from a term of a few days or 

 even hours, to a term of 9 or 10 months, and from single- to 

 many-broodedness. 



Larval Life of Cicada septendecim. 

 The Cicadidae offer the most notable exceptions, and, as 



