10 N. H. AGRI. EXPERIMENT STATION [Bulletin 243 



compact mass. Two short tubes extend up from the upper side of the 

 thorax. These are the air-tubes or breathing-trumpets. Extending from 

 the thorax is the slender, curved abdomen composed of nine segments. 

 At the end of the abdomen on the eighth segment are two thin, leaf -like 

 appendages called the swimming-paddles. Through the body wall of the 

 pupa can be seen traces of the adult organs (eyes, wings, legs, etc.) 

 which are rajiidly developing. 



The pupa breathes at the surface by means of the breathing trumpets. 

 It is lighter than water and floats to the surface when at rest. In order 

 to remain at the bottom the pupa swims under plants or debris which 

 hold it down. A single species (Mansonia) does not come to the 

 -surface but obtains air from water plants by thrusting the breathing 

 trumpets into the roots. 



The pupal period is short, generally varying from one day to about a 

 week. Its length is dependent on temperature ; the higher the temper- 

 ature the shorter the pupal period. 



When the pupa is fully developed it floats at the surface and gradu- 

 ally pumps air into the pupal skin until the pressure splits it down the 

 back. The adult mosquito, which has formed inside the pupal skin, then 

 works its way out and rests on the empty skin or climbs upon some sup- 

 port above the water. The newlj' emerged adult is soft and white in 

 color, but in the course of a few hours the body hardens, the wings ex- 

 pand and the normal color is assumed. 



LIFE HISTORY 



All mosquitoes go through the four different stages described above, 

 I.e., egg, larva, pupa, and adult. The period from the egg to the adult 

 is called a generation or a brood. A generation begins with the laying 

 of the egg by the adult mosquito. From the egg hatches the larva, which 

 feeds and grows, moulting, or shedding its skin, four times during growth. 

 After the larva is full grown, and at the time of the fourth moult, it 

 transforms to the pupa. Great changes occur in the insect during the 

 Ijupal period, and when these are completed, the pupal skin is split and 

 the adult mosquito emerges. After a varying period, during which mat- 

 ing occurs, the females lay eggs for a new generation. If these four stages 

 are completed but once each year, the mosquito is said to have one gen- 

 eration or brood, if twice a year, two generations, etc. The generations 

 and changes which an insect passes through in a single year are called its 

 life history. 



New Hampshire mosquitoes have several types of life history, examples 

 of which are briefly outlined in the following paragraphs. 



Most of our common woods mosquitoes (Aedes) have a single gener- 

 ation a year. The winter is spent in the egg stage, and the larvae hatch 

 in the spring in the early pools formed by melting snow and spring 

 rains. The adults emerge in May and deposit their eggs on sod, mud 

 or dead leaves in depressions or moist areas where water is likely to col- 

 lect. The eggs will not hatch until the following spring, even though 



