October, '11] GAHAN: XYLOCRABRO STIRPICOLA PACK 431 



I wish to acknowledge the assistance in the work upon which 

 this paper is based of Dr. L. O. Howard and Messrs. F. C. Bishopp 

 and W. A. Hooker. 



A NOTE ON XYLOCRABRO STIRPICOLA PACK 



By A. B. Gahan 



While records of the nesting habits of Crabronidse are not wanting 

 in entomological literature, the following observations are believed 

 to be of sufficient interest for publication. 



Early in March of the present year (1911) the Entomological 

 Department of the Maryland Experiment Station received from a 

 correspondent in Hagerstown a lot of twigs of Catalpa bungei, accom- 

 panied by a letter stating that a young tree was being badly injured 

 by some insect boring in the twigs. Examination of the twigs revealed 

 the fact that they were being utilized by some species of Crabronid as- 

 a nesting place. In some cases the stems had been hollowed out to 

 a depth of twelve to fifteen inches, and had, of course, been killed 

 for that distance. Some twigs contained as many as twenty-five or 

 thirty of the larvae, each in its separate cell. 



The larvae at time of receipt were plump, pure white grubs with 

 the abdominal spiracles quite prominent. Each was enveloped in 

 a thin, pale, brownish cocoon. They were evidently just beginning 

 to pupate, as the constriction between the abdomen and thorax was. 

 already appearing. 



The cells containing the larvse were separated by chewed up bits 

 of the pith, and in the end of each cell was a mass of fragmentary 

 remains of the insects which had served as the larval food. Examina- 

 tion of these fragments indicated that the principal part of the food 

 had consisted of a small metallic blue-green Dipteron of the family 

 Stratiomyidae. In some instances the remains of a grayish species, 

 apparently of the same family, were found. 



Adults were obtained from the twigs on May 8, 1911, and proved 

 to be Xylocrahro stirpicola Packard. Professor Riley has recorded 

 the finding of nests of this species in Osage Orange, and there are 

 other records of its having been found in raspberry. The probable 

 explanation for its choice of this catalpa as a nesting place and the 

 accompanying injury, is to be found in the fact that the tree had evi- 

 dently been pruned, leaving the soft pith exposed and furnishing an 

 ideal and inviting place for the wasp to nest. 



