SEXUAL CHARACTERISTICS OF THELIA 545 
gonads of an individual were all given the same number and a 
careful record kept of date, fixation, characteristics of pronotum 
and genitalia, and size of parasites, together with any excep- 
tional condition worthy of record. This was done for every 
specimen. 
Nymphs of all stages were fixed whole in Petrunkevitch’s 
fluid warmed to 50°C. The duration of fixation varied, with the 
size of the nymphs, from one hour for the smallest up to twenty- 
four hours for the largest. 
In making preparations of the genitalia, the non-chitinous 
portions were removed by heating in a solution of caustic soda 
and then trimming the preparation with a fine scissors and scalpel 
under a binocular microscope. They were then dehydrated and 
mounted in balsam. 
Sections were made through the bodies of adults and nymphs. 
In this work the celloidin-paraffin method (Kornhauser, ’16) 
was invaluable. Sections were made 10u in thickness, and it is 
possible to cut the hardest chitin without tearing the ribbons 
or nicking the knife. The gonads were cut 6, in thickness, and 
stained in Heidenhain’s haematoxylin and Congo red. 
All the figures (with the exceptions of numbers 7, 8, 18, 32 to 
35, 53, 54) are untouched photographs made with Spencer 
micro-teleplat objectives 8 mm., 24 mm., and 60 mm. In the 
24-mm. and 60-mm. objectives, iris diaphragms were inserted. 
The non-photographic figures are drawings made with the aid 
of a camera lucida. 
4, BRIEF ACCOUNT OF THE LIFE HISTORY AND HABITS OF THELIA 
Thelia bimaculata is the largest and one of the commonest 
membracids of northeastern United States. It feeds exclusively, 
as far as is known, on the sap of the common locust (Robinia 
pseudo-acacia L.). It is found on the trunk or larger branches 
of this tree. Adults occur from July to October. Association 
with other organisms is nicely seen in this docile, domesticated 
homopteran which is constantly attended by ants andis imposed 
upon by internal and external parasites. Hymenoptera live 
within its body, mites attach themselves to the exterior, and 
