414 W. D. FUNKHOUSER 



have fallen (Funkhouser, 1915 b: 142 and 1915 f: 185), and a number 

 of forms may regularly be taken late in November even when the autumn 

 has been cold. 



The condition of the host plant is believed to have an influence on the 

 life history of the membracid, but in most cases the conditions concerned 

 have been of a general rather than of a specific nature. As a whole the 

 Membracidae seem to prefer younp; plants to old ones, and favor twigs 

 and stems not over two years of age. Saplings are more likely than old 

 trees to harbor the insects, and the young shoots and buds of annuals 

 rather than the main trunk. Often water sprouts at the base of a tree are 

 covered with membracids wliile the tree itself is hardly molested; this has 

 been noticed particularly in the cases of Atymna castanea and Ceresa 

 borealis. Other observations made on this subject may be entirely 

 accidental but should perhaps be mentioned. It has been noticed that 

 oaks severely infected with galls were seldom chosen by Membracidae; that 

 shrubs and vines on which aphids were numerous likewise were free from 

 the insects of this family; but that, peculiarly enough, heads of goldenrod 

 which were stunted or " stung " were most likely to have colonies of 

 Puhlilia concava on them. In the last-named case it was thought that the 

 membracids themselves might be responsible for the condition of the host, 

 but there is no evidence to show that this is the case. Mr. Knight reports 

 that in Batavia, where the species is common, he has noted the same 

 tendency. 



From the preceding field data it seems logical to conclude that moisture 

 and warmth hasten the development of eggs and nymphs while opposite 

 conditions retard such development. Collecting has shown that in general 

 more membracids are taken on warm days than on cool days, and that 

 the insects are more active during the hottest days of the season. It has 

 already been noted that the Membracidae prefer sunny spots, open 

 growth of foliage, and positions close to the ground. 



It is evident, however, that the factors entering into the problems of 

 ecology are so complex that no results can be accepted as proved unless 

 all other factors than the one concerned have been eliminated, and this 

 would be possible only by an elaborate series of studies extending over a 

 great number of years. Naturally any influence that hastens or retards 

 the hatching of eggs or the development of nymphs would advance or 

 delay the dates for mating and oviposition. The variation in these dates 



