no. 2173. A REVISION OF THE BEMBICINE WASPS— PARKER. 125 



Many other investigators have also contributed to the knowledge 

 of the life and activities of Bembix, and the names of those to whose 

 works I have had access are given in the bibliography appended. 

 Among these there are two, Fabre and Wessenberg-Lund, whose 

 observations require further consideration here. Fabre maintains 

 that the flies stored by Bembix are always dead when placed in the 

 nest, and he suggests three possible explanations of this practice on 

 the part of Bembix: (1) Bembix does not know how to paralyze her 

 prey; (2) the delicate character of the constitution of the fly is such 

 that death is brought on instead of paralysis; or (3) the nervous sys- 

 tem of the fly is not suited to paralysis. Fabre does not state posi- 

 tively that the failure of Bembix to paralyze her prey is due to one of 

 these three causes, but he sees no other means of explaining the 

 departure from a practice so universal among the digger wasps. 

 Wessenberg-Lund maintains, as does Fabre, that the flies stored by 

 Bembix are killed and not paralyzed when captured; but he rejects 

 Fabre's suggestions as to the probable cause therefor and finds the 

 reason in the structure of the wasp herself. He enters into a critical 

 discussion of the form of the abdomen of various types of wasps and 

 bees and compares the form of the abdomen of those that are known 

 to paralyze their prey with that of those in which the sting is not 

 used for that purpose. He finds that the stalked abdomen, such 

 as is possessed by SpJiex, is associated with the instinct to paralyze, 

 and arrives at the conclusion that this form of abdomen is necessary 

 for the performance of this function. Consequently his answer to 

 the question, " Why does Bembix not paralyze her prey?" is that she 

 can not. Her abdomen is so formed as not to permit her to do so. 



Thus, both Fabre and Wessenberg-Lund maintain that Bembix 

 rostrata does not paralyze her prey, but each explains this departure 

 from what is the usual practice of digger wasps on different grounds. 

 Fabre finds the cause in the character of the prey, Wessenberg-Lund 

 in the structure of the wasp. If these investigators insist that this 

 departure is true only for B. rostrata, as I believe they do, it is possible 

 that they may be right. But if they maintain that this departuro 

 is true for all species of Bembix they are wrong; for at least one species, 

 Bembix spinolae Lepeleticr, both possesses this power and makes use 

 of it as the following observations show. 



On June 13, 1914 I observed a female of Bembix spinolae enter her 

 nest carrying a Ohrysops fly. After some time, probably about five 

 minutes, she emerged and was captured. I at once digged up the 

 nest and found in the brood chamber a single fly, the one I had 

 seen carried in. Upon the fly, which was lying on its back, was found 

 the newly-laid egg placed in its characteristic position, attached by 

 one end to the thorax at one side just posterior to the base of the 

 wing. I carefully removed the fly and egg from the nest and placed 



