1913] Life-History of a Bee-Fly. 215 



II. Life History of the Parasite {Spogostylum). 



1. Adult Habits. 



The adult is a bright shiny velvet black fly with the basal 

 two thirds of the wings black and the distal third transparent. 

 (Fig. 1). It occurs in July and August, in open spots on sandy 

 soil, especially in the kinds of situation shown in Fig. 3, where 

 herbaceous vegetation and flowers are numerous. It is com- 

 monly associated with other bee flies such as Anthrax impiger 

 Coq., Anthrax fulvohirta Weid., and Anthrax molitor Loew. 

 which are much more abundant and often visit flowers in 

 numbers, also Exoprosopa, which probably lays in the burrows 

 of the Bembecid wasps. The habits of the male Spogostylum 

 have not been observed. The female usually alights near the 

 ground on the lowest plants or on sticks and leaves. In sunny 

 weather she starts with remarkable swiftness when a shadow is 

 passed over her but appears not to be stimulated by the pres- 

 ence of the observer under other conditions. In cloudy weather 

 the writer has shaken an insect net within a few inches of one of 

 the flies without causing her to move. The food habits have 

 not been observed but a single individual lapped sugar and 

 water from a piece of paper, while in captivity. 



2. Egg Laying. 



The female flies about two inches above the clear open 

 sand in an irregular somewhat zig-zag fashion until apparently 

 b\' chance its eyes pass above a hole in the sand, (Figs. 2 and 3). 

 When this happens, the fly suddenly halts and moves backward 

 and downward in a curved course. At the same time the 

 abdomen is thrust forward so that it touches the surface of the 

 sand at a point 5 to 10 mm. from the edge of the hole. The impact 

 of the abdomen upon the sand is sufficient to perceptibly move 

 small particles, some of which appear to fall in the burrow. 

 The thrusts are usually repeated a number of times. After 

 each movement, the fly returns to approximately, the posi- 

 tion at which the thrust began. The sight of the hole 

 below the eyes acts as a trigger which sets off the thrusting 

 reflex. The host larvae frequently rest in the burrow some 

 distance below the surface. On two occasions the fly stopped 

 thrusting when the larva appeared near the surface. The size 

 and shape of the hole appear not to be of prime importance. 



