viii, B, 1 Mitzmain: Stomoxys calcitrans Linnseus 33 



from twenty to twenty-six hours. At a temperature of 20° 

 to 22° C, eggs hatch in from forty-eight to sixty hours, depend- 

 ing on the humidity. Eggs kept in a darkened closet hatch 

 four to six hours sooner than individuals of the same brood 

 kept at the same temperature in a room exposed to light from 

 windows. 



The influence of moisture on the incubation period may be 

 illustrated by the following observation. A fly was placed in 

 a test tube while in the act of laying eggs. Forty eggs were 

 deposited, distributed along the sides of the tube. The first 

 Q^g was observed to be laid at 11.40 a. m., and the remainder 

 during thirty minutes. A piece of filter paper half the length 

 of the tube was soaked with salt solution and placed with the 

 eggs. Note was taken where the first egg of the batch was 

 laid, which was about 3 centimeters from the end of the mois- 

 tened paper and close to the end of the cotton plug. At 1 p. m. 

 of the following day the eggs at the bottom of the tube, where 

 the moisture accumulated, commenced hatching. All of the 

 eggs, except the first one laid, hatched before 2.30 p. m. of the 

 same day. This egg hatched upon the day following at 11.20 

 a. m., nearly one day later than the eggs in the moistened end 

 of the tube. The larva from this egg appeared quite normal; 

 it was observed to crawl immediately toward the moisture at 

 the bottom of the tube. This phenomenon appears to be in 

 keeping with notes made of field conditions, and when flies 

 are reared in glass vessels in the laboratory. 



LARVAL LIFE 



The young larva loses no time in consuming whatever de- 

 sirable food may be present. The feeding seems to be con- 

 tinuous, broken only by the short period of seclusion just before 

 the formation of the pupa. Food seeking is relatively a passive 

 process with this insect; the mother provides for the life of 

 its progeny, in laying the eggs only where there is an abundant 

 food supply. 



Very little time is consumed by the larva in adapting itself 

 to food conditions. The bloody excreta of the mother, if pres- 

 ent, is first consumed, then the more inviting portion of the 

 animal manure is devoured. The color of the insect, at first 

 waxy or creamy white, rapidly assumes the color of the ingested 

 food. This is pale green at first, changing, from the posterior 

 end to the anterior portion, to pale brown. The larval cuticle 

 does not become darker before six to seven days. 



115513 3 



