XVI] BIONOMICS 291 



Stuhlmann found that in order to catch females it was neces- 

 sary to use some animal as a decoy, but even then they were 

 much more difficult to catch than males. The gravid females 

 are probably much more wary and move about less than the 

 males, and are consequently more rarely caught. 



Reproduction. In nature the flies have occasionally been 

 observed in coitu on tree-trunks. Stuhlmann noticed that 

 in captivity only freshly hatched females received the males, 

 but possibly the behaviour of the flies was modified by the 

 artificial conditions. 



Stuhlmann has given a very complete account of the 

 breeding habits of this species in German East Africa and the 

 following observations are taken from his report. 



When females were kept at a temperature of 23 to 25 C., 

 they gave birth to larvae at intervals of about 12 days, but by 

 varying the temperature the interval could be varied from 

 10 to 21 days. In three and a half months one female gave 

 birth to eight larvae, of which, however, two were dead. The 

 extrusion of larvae apparently proceeds uninterruptedly the 

 whole year round, but the intervals are prolonged during the 

 cold season. 



The freshly extruded larva is of the usual Glossina shape 

 and its behaviour previous to pupation has been well described. 



" If the new-born larva be placed in a glass dish or on 

 blotting-paper, it crawls about for a time exactly like an 

 ordinary fly-maggot, after which it becomes stationary and 

 soon contracts, its chitinous integument thickens and darkens, 

 and in about three-quarters of an hour it has assumed the 

 appearance of a coarctate pupa. If, however, the larva be 

 transferred to moderately damp sand, it at once burrows into 

 it, making a straight tunnel ; thus in one case a larva penetrated 

 to a depth of 8-5 cms. Under such conditions, from an hour 

 and a quarter to an hour and a half elapsed before the change 

 to the pupal state was completed. In dry sand a larva did not 

 burrow so deeply, since, as it burrowed, the sand continually 

 fell in, but nevertheless it reached a depth of 2 to 3 cms. We 

 may assume that in nature the larvae behave in a similar way ; 

 the fly will deposit its offspring on a spot which is sheltered 



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