Notes on the Commoner Species 163 



able. It will not multiply in foul water, and Dr. 

 Smith does not find it in salt marshes. It will breed 

 successfully in hydrant water. The species enjoys a 

 general distribution over the Eastern United States. 

 It does not migrate in swarms, but Dr. Smith says 

 that it can fly perhaps five miles, and will gradually, 

 during a season, increase in numbers in a place by in- 

 dividual migration, being a considerable nuisance in 

 some localities. We found the insects to be somewhat 

 of a pest outside the house in Baton Rouge ; but few 

 came in, though the house was not screened. It 

 seemed to be worst in the fall, and was troublesome 

 in some parts of the city about the end of July. The 

 adults were taken plentifully out-of-doors all the 

 year, but hibernation in the egg stage is the rule 

 farther north. There is laid one batch of single 

 eggs deposited on top of the water, where, in the 

 laboratory, they sometimes floated for a month or so. 

 As a rule, however, they soon sink to the bottom, 

 where they will lie for from four days to a year 

 before hatching. They will emerge without agitation, 

 but this accelerates matters. A few larvae appear at a 

 time, the process extending over a number of days. 

 The insect bites once, rarely twice, before laying, the 

 oviposition occurring from two to twelve days after 

 the meal, the average being eight days, but on one 

 occasion in the spring it was as long as twenty-six 

 days after feeding. The larval period is from six 

 to nine days, the pupal two to six days. In warm 

 weather, out-of-doors, the whole cycle may be com- 

 pleted in five and one-half days. The larvae were 

 found out-doors in Baton Rouge from February 22 



