118 MOSQUITOES OF NORTH AMERICA 



TIME OF ACTIVITY. 



Mosquitoes are generally looked upon as nocturnal in habits but this is prob- 

 ably true of only a small number of species. Our house mosquitoes of the genus 

 Culex are nocturnal. Culex quinquefasciatus, the house mosquito of the tropics, 

 is strictly nocturnal and bites in complete darkness. Many species of mosquitoes 

 are crepuscular, confining their activities to the twilight of evening and early 

 morning. This is the case with most Anopheles and the peculiarities of some of 

 the species, in this respect, are discussed in our chapter on malaria. The yellow- 

 fever mosquito (Aedes calopus) is strictly diurnal; its behavior is fully dis- 

 cussed in connection with yellow fever. In far northern regions the mosquitoes 

 are of necessity diurnal. One of us (Ivnab) found that the mosquitoes of the 

 Saskatchewan prairies are active throughout the day, during the hours of full 

 sunlight. At evening their attacks ceased, and indeed the rapid fall of tempera- 

 ture at that time puts an end to all insect activities. In the tropics, at least in 

 America, a large proportion of the species of mosquitoes are strictly diurnal. 

 It is true of many, if not all, the mosquitoes of the tribe Sabethini ; they are 

 forest inhabitants and fly about during the hours of full sunshine. The large 

 and showy members of the genus Megarhinus appear to be diurnal. Lutz 

 states that the males of Megarhinus solstitialis are seen flying rapidly by day. 

 Knab has found a female of Megarhinus septentrionalis sucking honey from a 

 flower in broad daylight. It is probable that all brilliantly colored mosquitoes 

 are diurnal. The species of Aedes of our northern woods appear to be cre- 

 puscular. Yet, while they are normally quiescent during full daylight, they are 

 easily aroused. The presence of food, in the shape of a human being, will attract 

 them, apparently from a considerable distance, as one can ascertain by remain- 

 ing in one spot for a time. Aedes canadensis, Aedes stimulans and related forms 

 attack viciously during midday. Aedes atropalpus will bite by day and we have 

 known it to bite so late in the evening that it could no longer be seen. Knab 

 found that at Winnipeg Aedes riparius came to bite in numbers during the 

 middle of the day ; it also bit at night in bright moonlight. Mansonia pertur- 

 hans is strictly crepuscular but in dark woods will attack in the daytime. 



Different situations are sought out by the different species to pass the time of 

 quiescence. Certain species which have become more or less associated with man 

 seek shelter within houses or other structures. Certain species of Anopheles 

 frequent cellars, out-houses and culverts, and certain species of Culex are even 

 more domestic. The majority of the species of mosquitoes, however, are practi- 

 cally never found in houses. They hide in the woods, on the under side of leaves, 

 upon tree trunks, in hollow trees or under old logs. The prairie species hide in 

 the grass. 



LONGEVITY. 



The question is frequently asked, how long a mosquito lives ; the adult form 

 alone being in mind. The males are very short-lived, in most cases probably a 

 matter of a few days only. Their only ofiice is to fertilize the female and this is 

 usnally very soon accomplished. Observations made by Knab in Saskatchewan 



