136 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



The variation in the length and depth of the burrow depends a great 

 deal upon its location. If it is constructed on a level spot the brood 

 chamber, as a rule, is not so far below the surface as it is when the 

 burrow is placed on a sloping site, and the wind by shifting the sand 

 may alter its depth, no matter where placed. In no case did I find a 

 burrow branched or with more than a single young within it. 



The wasp digs with great rapidity, but the length of time required 

 to complete a burrow varies with the condition of the sand and the 

 abundance and activity of the males. After a rain the sand is wet 

 and heavy and the work is laborious, and when the sand is quite dry 

 and loose it slides down into the entrance as fast as the wasp digs it 

 out. In fact, if the sand is very dry and loose the wasps can not con- 

 struct their burrows at all, and I have seen them work for half a day 

 without being able to get out of sight in the sand, whereas when the 

 sand is in good condition — i. e., shortly after a rain — a burrow can be 

 completed in the course of two or three hours or even less. 



Occasionally we find two and even three females contending for the 

 same burrow, and it is interesting to watch the struggle that ensues. 

 When the contestants are of the same size the argument becomes 

 decidedly strenuous. They push and shove and crowd each other 

 about the entrance to the burrow. One will gain the entrance only 

 to be seized by the wing or hind leg and dragged out by the other, 

 which, on gaining the entrance, is subjected to the same treatment 

 by her rival. Frequently as one of them seeks to enter the burrow 

 the other will pounce upon her back, seize her, and rising on the wing 

 carry her to a short distance and drop her without ceremony upon the 

 sand. These struggles sometimes last for hours with no decided 

 advantage to either and apparently no harm sustained by either. 

 The explanation of these contests apparently lies in the fact that, 

 owing to the great number nesting in the same area, two or more 

 burrows are constructed with their entrances quite close together, so 

 that one wasp in opening her burrow disturbs the entrance to the nest 

 of a neighbor, and if this neighbor is desirous of inspecting her nest 

 at the same time a fight ensues. 



When the burrow has been completed a single egg is placed in the 

 brood chamber at the extreme end. This is firmly fastened in an 

 upright position in the sand of the floor of the brood chamber. The 

 egg is white, cylindrical, and rounded at the ends. The eggs hatch 

 in from two to three days, and the larvae at first remain with the 

 posterior part of the body still attached within the egg shell, for the 

 egg is always placed so that the head of the developing larva is upper- 

 most, and it waves its anterior part about in search of food. No food, 

 however, is placed in the burrow until the egg has hatched. In this 

 respect Microbembex monodonta resembles S. Carolina as reported by 

 Hartman. Microbembex monodonta feeds its young on dead insects, 



