33 



Among 34 eggs kept for from 9 to 15 days at a temperature of f romr 

 42 to 45° F. none hatched when later removed to a higher temperature. 

 It may be noted here that drying of the square will also retard- 

 embryonic development, but this condition does not occur in the field^- 



Table IV. — Range in duration of egg stage. 



Number 



Duration of 



Number 



Duration of 



of eggs. 



egg stage. 



of eggs. 



Qgg stage. 





Days. 





Days. 



2 



2 



4 



5 to 6 



132 



2 to 3 



3 



8 to 9 



192 



\ 2 to 4 



6 



10 to 11 



15 



10 to 12 



42 



3 to 4 



4 



10 to 13 



96 



{ 3 to 5 



3 



13 to 14 



2 



13 to 15 



40 



4 to 5 







13 



{ 4 to 6 







The duration of the Qgg stage in boils does not appear to differ^ 

 greatly from that in squares. 



HATCHING. 



While still within the Oigg the larva can be seen to work its mandi- 

 'bles vigorously, and although a larva has never been seen in the act 

 of making the rupture which allows it to escape from the o^gg^ it is- 

 believed that the rupture is first started by the mandibles. The 

 larvae do not seem to eat the membranes from which they have escaped, 

 but owing to the extreme delicacy of the skin it is almost impossible 

 to find any trace of it after the larva has left it and begun feeding on^. 

 the square, the membranes having been found in only a few cases. 



HATCHING OF EGGS LAID OUTSIDE. 



It occasionally happens that a female is unable to force an ^gg into- 

 the puncture prepared to receive it and the ^gg is left on the out-- 

 side of the square or boll (PL III, fig. 9). Eggs so placed usually 

 shrivel and dry up within a short time. To test the possibility of a 

 larva making its way into a square from the outside, a number were 

 protected from drying. Of the 19 eggs tested, 6 hatched in from 2 to^ 

 3 days. In no case, however, was the young larva able to make its- 

 way into the square and it soon perished. The hatching of eggs laid 

 outside is of no importance, since the larvee must perish without 

 doing any damage. 



EATING OF EGGS DEPOSITED OUTSIDE. 



The number of eggs left outside increases as the female becomes^ 

 weakened, and is especially noticeable shortly before her death. Re- 

 peated observations have shown that unfertilized females normally 

 16780— No. 51—05 3 



