140 THE EARLY STAGES OF TABANID^ 



a period which seems to be rather long. In 1907, Lecaillon found 

 that eggs which were laid on June 11 had not yet hatched on June 8. 

 Eggs collected on July 1 1 , which had certainly been laid a long time, 

 produced larvae on July 22. Embryonic development is, however, 

 completely terminated at the end of twelve or thirteen days, be- 

 cause, after that period, it is sufficient to rub the egg mass only 

 slightly in order to cause the larvae to hatch. 



It can be assumed, consequently, that the larvae do not leave the egg 

 shells in which they have developed, until they need food; from the 

 time of their formation to that of hatching, they probably find an 

 efficient protection inside the egg shells. Perhaps also the egg shell 

 which has to be pierced by the larvae in the act of hatching is of a vari- 

 able resistance according to the conditions of the environment. In 

 a damp environment, for instance, the shell would be less resistant 

 than in a dry atmosphere, and the larvae could hatch much more 

 easily in the first than in the second instance. The larva appears in 

 this case to be adapted to remaining enclosed in the chorion of the 

 egg for a time long enough to wait for favorable atmospheric condi- 

 tions. Lecaillon has not made exact studies to determine this point. 



When the larvae hatch, they remain sometimes for a few moments 

 on the surface of the egg mass. They carry out very varied move- 

 ments of contraction and finally fall to the ground into which they 

 burrow immediately. Often they are also attached to one another, 

 forming sort of batches which finally lose hold on the egg mass and 

 fall to the ground. They are, as Lecaillon says in 1906, extremely luci- 

 fugous (negative phototropic), and they could not be easily destroyed. 



Immediately after hatching, the larvae are white in color and this 

 color is retained. The body is also somewhat transparent, and the 

 arrangement of different internal organs can be observed with facility. 

 It is seen that in the middle intestine there remains a rather large 

 quantity of nutritive yolk, a remainder of the primitive egg contents. 

 At the level of the yolk the intestinal tract is opaque. When placed 

 in damp earth, the young larvae appear not to take food for several 

 days. 



In order to ascertain whether these larvae were carnivorous, Le- 

 caillon supplied them with ant nymphae freed from their cocoons, 

 with flies killed previously, and with larvae of Chironomus. He 



