June-Sept, 1919.] DlCKERSON & WEISS : IDIOCERUS COGXATUS. 129 



NOTES ON THE EARLY STAGES AND LIFE HIS- 

 TORY OF IDIOCERUS COGNATUS FIEB., IN 

 NEW JERSEY. 



By Edgar L. Dickerson and Harry B. Weiss, 1 

 New Brunswick, N. J. 



This species was first observed by us during the summer of 191 7 

 on white poplar (Populus alba) growing in a nursery at Irvington, 

 N. J., and the following observations were made during the spring 

 and summer of 1918. 



The eggs of this species are deposited singly during the middle 

 and last of July in the new growth, terminal twigs usually being 

 selected. Any of the new wood is likely to contain eggs, but they 

 are found most plentiful in the last foot of the twig and more spar- 

 ingly toward the base and the extreme tip. The place of oviposition 

 is indicated by a somewhat irregular, pear shaped blister or swelling 

 about 1 mm. long and 0.5 mm. wide. In many cases, the cap of the 

 egg projects slightly from the surface of the twig. If the egg has 

 been inserted far enough to hide the cap, the bark around the cap 

 becomes somewhat corky and splits. Each egg is firmly embedded in 

 the bark tissue and not simply inserted in the bark as is the case with 

 the egg of Idioceras scurra. As a rule each egg is placed in a slant- 

 ing position with its long axis more or less at an angle with the 

 grain of the tissue. Sometimes eggs were found in irregular groups 

 of two or three, but more often singly. 



Hatching takes place from the middle to the last of May and the 

 young nymphs can be found on the unfolding tender leaves at the 

 tips of the twigs. The upper leaf surface seems to be preferred, 

 many of them resting close to the midrib at the base of the leaf. 

 Some however can be found on the lower leaf surface. As the 

 nymphs become older, they scatter, many resting on the stems of the 

 new growth usually close to a leaf petiole. On the whole, the upper 

 surfaces of new leaves are preferred. Here they blend with the 

 whitish bloom of the young leaves and only those with distinct 

 blackish markings are readily seen. Moulting takes place on the 

 1 The arrangement of the authors' names has no significance. 



