no. 2173. A REVISION OF THE BEMBICINE WASPS— PARKER. 127 



During the summer of 1914 I spent a great part of my time observ- 

 ing the nesting habits of three species of Bembioine wasps: Bembix 

 spinolae Lepeletier, Bicyrtes ventralis Say, and Microbembex monodonta 

 Say. The nesting site was a pile of clean sand on a vacant lot in the 

 city of Washington. The last of these three species I had observed 

 with considerable care the previous summer at Cedar Point, Ohio, 

 and what was observed in Washington simply corroborated the 

 facts previously obtained. 



BEMBIX SPINOLAE Lepeletier. 



In constructing her nest Bembix spinolae digs a sloping tunnel in 

 the sand varying from 5 inohes to 1 foot in length and, by enlarging 

 the tunnel at the end, forms a brood chamber which is from 4 to 6 

 inches below the surface of the ground. These nests are digged at 

 all times of the day; some females are busy at this work early in 

 the morning, others late in the afternoon. On dark, gloomy days 

 these wasps are inactive; they love the sunshine and the hottest part 

 of the day finds them most active. About an hour is required to 

 construct a nest, but the condition of the sand and the individuality 

 of the wasp are important factors in determining the time required. 

 When the nest is complete the wasp closes the entrance carefully 

 and then attacks the pile of sand thrown up in excavating the nest. 

 This she scatters in all directions and continues to work over the 

 surface until all evidence of the presence of the nest is completely 

 obliterated, which usually requires about five minutes. When this 

 has been done the wasp sets forth in search of prey. 



The length of time required to secure the first fly for the new nest 

 varied from 2 to 10 minutes. On the first fly placed in the nest the 

 egg is laid and the time spent in this operation varied from 5 to 12 

 minutes. On emerging from the nest after depositing the egg the 

 wasp shows renewed interest in the concealment of the entrance to 

 her domicile. She spends as much time in effacing the evidence of 

 the opening of the nest as she did in performing the same operation 

 when the nest had just been completed. In this oase she throws the 

 sand from all directions toward the entrance to the nest, whereas in 

 the previous operation she throws it away. B. spinolae stops up 

 the burrow not only at the entrance but also at a short distance from 

 the brood chamber. This I found true for every nest investigated. 

 In the evening the female wasp usually returns and spends the night 

 within the nest, but not in the brood chamber. In every oase where 

 I found a female within her nest she was found between the obstruc- 

 tion at the entrance and the one near the brood chamber. 



The males of B. spinolae spend much of their time flying about over 

 the nesting area seeking the females and quarreling among themselves. 

 Copulation occurs on the wing. From time to time the males leave 



