1913] Life-History of a Bee- Fly. 221 



« 



operation. The two posterior spines are thrust into the floor 



of the burrow and the curvature is increased, which cause the 

 head to move back as shown in Fig. 15. After a number of 

 hoeing movements, the pupa usually wriggles backward carry- 

 ing the sand with it by means of the bristles and again wriggles 

 forward until the head is in contact with the end of the burrow. 

 The hoeing movement is repeated or less frequently the body is 

 rotated, the hooks serving as a boring organ. 



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Figures 15-16. Emergence from the ground. 

 Fig. 15. Diagram showing the movement of the pupa in digging its way out of 



the ground. Natural size (a). 

 Fig. 16. Showing the burrow and pupal cell of the host with the path dug by the 



pupa of Spogostylum. 



The boring movement was observed in the case of one in- 

 dividual, the host of which had been confined in a glass tube 

 eight inches long and one and one-half inches in diameter. 

 The burrow and pupal cell of the host were constructed in 

 contact with the glass. Much of the life history of one parasite 

 was thus observed. The digging of the parasite pupa began at 

 night, and was not noted until the middle of the next forenoon 

 (July 15), [began in pch of Fig. 16, p. 221]. During the last eight 

 hours the larva progressed at the rate of 1 cm. per hour. It moved 

 in contact with the glass and traveled more than once around the 

 tube just inside the glass. The total distance through which 

 the parasite dug was about 24 cm. Apparently immediately 

 upon reaching the surface the fly emerged. It left the pupal 

 integument sticking in the burrow. The emergence of the fly 

 was not observed as the last centimeter of digging was accom- 

 plished in less than 20 minutes and the fly emerged between 

 observations. The adult was found resting on a small blade 

 of grass near the hole. This adult lived only about two days. 



