June, 1929] MOSQUITOES OF NEW HAMPSHIRE 9 



list of species, although many of them may occasionally be found 

 breeding in other tj^pes of pools. 



Most mosquito lan-ae feed on organic matter, {irincipally the micro- 

 scopic plants and animals, both living and dead, which live in water. 

 These tiny organisms form a scum on the surface of standing water 

 and collect as an ooze on the bottom of the pool and over the plants 

 growing in the water. The larvae sweep this ooze or scum into their 

 mouths by means of the mouth brushes. Nearly all of our mosquito 

 larvae are bottom feeders, but some of them will feed occasionally at the 

 surface, and Anopheles always feeds on the surface scum. The larva of 

 one New Hampshire mosquito (Psorophora) is predaceous, feeding on 

 the larvae of other mosquitoes. 



It is necessarj' for most mosquito larvae to come to the surface to 

 breathe. The tip of the air-tube is thrust through the surface film, and 

 air is taken in through the tube. By means of an apparatus on the tip 

 of the air-tube the larva is able to hang motionless at the surface, sus- 

 pended from the surface film. Most larvae hang at the surface with the 

 body at an angle, but Anopheles lies parallel with and close to the sur- 

 face film. The anal gills assist in breathing while the larva is under the 

 water. 



The length of time the larva can remain under water varies with the 

 different species. A few rare or non-biting species seem to be able to 

 breathe entirely by means of the anal gills, seldom or never coming to 

 the surface for air. One species (Mansonia) breathes by thrusting its 

 pointed air-tube into the roots of sedges growing in the water and ob- 

 taining air from the plant tissues. It remains attached and never comes 

 to the surface. 



The length of the larval period is dependent on temperature, food sup- 

 ply, and the life cycle. Most mosquitoes have a short larval period, 

 varj-ing from six or seven days to several weeks. In general the higher 

 the temperature and the more abundant the food, the shorter is the 

 larval period. In those species hibernating as larvae the overwintering 

 larvae may live for several months. One of the.se which has but a single 

 generation each year may have a larval period of over eleven months. 



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

 transforms to the pupa. Changes go on for some time in the larva, and 

 when it sheds its skin for the last time the pupa emerges fully formed. 



THE PUPA 



The ijupa is the transforming stage of mosquitoes. During this pe- 

 riod the insect goes through the conii)licated process which changes it 

 from the worm-like larva to the adult mo.squito. The pupa does not 

 feed, but subsists on the food stored up by the larva. It differs from 

 the pupa of most insects in being active, and is often called a tumbler 

 from its habit of swimming end over end. 



All mosquito pupae are brown in color and somewhat resemble a large 

 comma in shape. The head and thorax are grown together to form a 



