MOSQUITOES AND FLEAS. 29 



from two to four days and that some of the larvae cast their first -kin 

 three to four days later, and a second skin two to six days later. 

 On July 1") another series was began. The eggs collected on this 



date began to hatch on the 17th and all had hatched "by the morning 

 of the 18th. July 21 some of them had cast the first skin. 



August 1 the first one spun up: August 3, two more: August 6, two 

 more. At this date the first one which constructed its cocoon turned 

 brown. August 7 one full-grown larva transformed to papa without 

 spinning a cocoon. August 12 the first adult emerged. A summary 

 for this lot shows that the eg<^ hatch in from two to four days and 

 that the larvae cast the first skin from five to seven days later. Some 

 spun up sixteen to twenty days after hatching, and the imago appeared 

 six days later. 



Observation of these last two lots shows that the larv?e are very apt 

 to die if kept too dry or too moist. They also need plenty of air. 



July 20 another series was begun. Eggs collected on this date 

 hatched the following day. July 24 the first skin was cast: July 26, in 

 one case a second skin was cast. July 27 three more cast a second 

 skin, and on this date one individual spun its cocoon. July 29 three 

 more began to spin: on July 30 many more. On July 30 the first one 

 that began to spin was found to have changed to papa. August 2 

 many cocoons were found. Some of the larvae, disturbed while spin- 

 ning, left the incomplete cocoon and transformed to pupa outside of it. 

 Most of the advanced specimens were placed in alcohol, and it was not 

 until August 14 that an adult was allowed to emerge. 



This series of observations showed that the egg^ hatched about one 

 day after being placed in the vessels. The larvae cast their first skin 

 in from three to seven days, and their second skin in from three to four 

 days. They commenced spinning in from seven to fourteen days after 

 hatching, and the imago appeared five days later. 



From these observations it appears that in summer at Washington 

 many specimens will undergo their transformations quite as rapidly as 

 Mr. Simmons found to be the case at Calcutta, and that an entire gen- 

 eration may develop in little more than a fortnight: also that an e» — 

 of moisture is prejudicial to the successful development of the insect 

 and that in the same way the breeding place must not be too dry. The 

 little particles of blood found among the eggs on the cloth upon 

 which the infested animal has slept are probably the excrement of the 

 adult fleas. This substance in itself, together with what vegetable 

 dust is found in the places where these larva' rear themselves, sufiices 

 for the larval food. 



k e:\iedies. 



Flea larvae will not develop successfully in situations where they are 

 likely to be disturbed. That they will develop in the dust in the cracks 

 in floors which are not frequently swept has been observed by the 



writer. The overrunning of houses in summer during the temporary 



