1933] Tropisms Effecting Copulation in the Bed Bug 115 
THE TROPISMS EFFECTING COPULATION IN THE 
BED BUG. 
By Ezekiel Rivnay 
The fact that the female of the bed bug has a special 
asymmetrical opening for the reception of the male 
copulatory organs, rather than the ordinary vagina, makes 
this study extremely interesting. It is astonishing that 
this fact escaped the attention of early investigators and 
that the copulatory organs of so well-known an insect were 
unknown until comparatively recent years. A complete and 
detailed description of copulation in bed bugs was pub- 
Fig. I 
Fig. 2 
Ventral view of abdomen of the bed bug; Fig. 1, male; Fig. 2, female 
lished by Hase (1918), and the most complete study of the 
sexual organs and their functions was made by Cragg 
(1914, 1920 and 1925). Copulation of bed bugs was ob- 
served by the present writer during the course of rearing 
them in connection with other studies. The peculiarity in 
this act is that the male mounts the female obliquely in 
such a manner that his head falls over the left side of the 
pronotum of the female; his left legs grasp the posterior 
part of her abdominal margin ; and his posterior abdominal 
segment is bent deeply so that the tip reaches the right side 
