igio] Life Cycle of Horma phis hamamelidis 145 



At Cold Spring Harbor, where these observations were made, 

 three birches are present: Betula lenta is common, B. popuHfoHa 

 is uncommon, and B. lutea is rare. B. nigra is said to occur, but 

 was not found. Winged migrants were placed on the leaves of 

 the first three of these species in the evening; those on leaves of 

 trees outside had left by 9 a. m. the next day; some of those on 

 branches in the laboratory remained during the day, and were 

 seen as late as 4 p. m., but had left by 8 a. m. on the following 

 morning. They appear not to have deposited any young, since 

 none appeared on the leaves during the following two weeks. 



A branch of witch hazel with leaves bearing galls, and one 

 of a birch (B . lenta) , growing near together, were enclosed in the 

 same bag. After about three weeks the bag was opened, when 

 sexual individuals were found on the witch hazel leaves, but none 

 on the birch. 



The observations show that in the vicinity of New York, 

 Hormaphis has a much simpler life history than that ascribed to 

 this species by Pergande for the vicinity of Washington. It 

 would s^em to follow, either that further south there is a longer 

 life cycle including an alternate host, or that Pergande has inter- 

 calated in the life cycle of this species several generations of some 

 other (aleurodiform) species. Fortunately the question can be 

 very simply decided by making a few serial sections of the winged 

 migrants in the galls found in the District of Columbia. 



Pergande' s statement is so definite and detailed that it scarcely 

 seems possible that he could be mistaken in regard to the life 

 history of the Washington form. For example, he states on page 

 17, regarding the third generation: "Toward the middle or end 

 of June the insects cast their third or final skin and assume a 

 most remarkable mimicry: in fact, mimic now so closely certain 

 Aleurodids that for some time I was completely deceived as to 

 their true nature, which only after close examination of numerous 

 specimens, in connection with its earlier stages, was disclosed. 

 When seen on the leaves they are to all appearances true Aleu- 

 rodids, both in shape and size, resembling to some extent the scale- 

 like form of Aleurodes corni or related species." The fourth and 

 fifth generations are also aleurodiform. "With the appearance 

 of the sixth generation a new cycle of forms begins to make its 

 appearance, in which the aspect of the insects has changed com- 

 pletely, so much so that the casual observer would fail to trace 

 a connection between them and the Aleurodiform generations. 



