1954] Creighton and Gregg — Cryptocerus texanus 47 
After the plaster hardened the slide was removed and 
suitable chambers and passages were cut in the plaster. 
The slide was then put back in place and held in position 
with rubber bands. In both these nests the action of the 
major in the passages could be easily observed and the 
passages could be enlarged when necessary. 
Figure 3. a, lateral view of the major of Cryptocerus texanus in the 
phragmotic position in a hollow twig; b, cephalic disc of above maji^r 
seen in full-face view. 
It soon became apparent that if the passages were made 
to fit the cephalic disc of the major closely, this caste would 
not enter them at all. Since the medias and minors would 
use such passages freely there was no reason to suppose 
that an 3 Tthing other than the size of the passage determined 
the refusal of the majors to use them. When such passages 
were enlarged the majors used them without hesitation. 
But this behavior indicated that the major of texanus can- 
not or will not go into a passage whose size and shape 
closely approximates that of the cephalic disc. The reason 
for this appears to lie in the fact that the major of texanus 
occludes the nest opening not only with the cephalic disc 
