THE SAND-LOVING AMMOFHILA 241 



on, but since they could not outdistance us, we soon found 

 that, after they had travelled thus from three hundred to 

 five hundred feet, they invariably turned back. If we con- 

 tinued to follow them on their return, we would arrive nearly 

 at, and sometimes beyond, the starting-point, where they 

 would usually disappear in the weeds. We could see no 

 females at work along the roadsides. Even though the 

 males should migrate along the highways, this alone would 

 not be a factor in their dissemination while the females 

 remain near the old home, since the female alone decides the 

 home site. The abundance of males shows that they do not 

 die off as early as do the males of Benibvx nubilipennis. 



We have been able to examine only two species of Ammo- 

 phila in the field, A. pictipennis and A. procera, but we feel 

 that there is some little evidence to indicate that A. picti- 

 pennis is phylogenetically older than A. procera. A. picti- 

 pennis ingeniously carries her prey underneath her body with 

 the smooth, dorsal side against the earth. She is so small 

 that the prey must drag on the ground, and, if the ventral 

 surface were against the ground, the legs would offer re- 

 sistance; so we invariably find her carrying it with the 

 smooth, rounded surface downward. A. procera carries her 

 prey in precisely the same manner, but the point that we 

 would make here is that the wasp is so large and its legs 

 so long that, when the caterpillar is hugged up close to the 

 body, it is well off the ground, so here we see the uselessness 

 of turning the scratchy legs from the ground. Yet the 

 habit persists, and we can see in the habit only the vestige 

 of one which was a necessity in the older species. A. procera 

 often seems only a giant variety of A. pictipennis, since it is 

 practically the same in color, form and all respects except- 

 ing size. One can easily imagine certain individuals of the 

 pictipennis group, a little larger in size, getting larger cater- 

 pillars, and the consequent effect of a superabundance of 



