90 PRACTICAL ZOOLOGY 



listless activity in the world's work that counts mightily against 

 the wealth-producing power of the people. Finally it means 

 from two to five million or more days of sickness with all its 

 attendant distress, pain of body, and mental depression to some 

 unfortunate individuals of those five states (Herrick). 



Breeding Habits of Anopheles. As in thte case of the house 

 fly, the breeding habits of the mosquito furnish the key for its 

 destruction. Many kinds of mosquitoes lay their eggs in masses 

 that float on the surface of the water (Fig. 54, C), but Anopheles 

 deposits them singly, often close together (Fig. 54, E). The 

 larvae, which hatch from the eggs in about three days, remain in 

 the water, feeding on the green scum on the surface. Their posi- 

 tion in the water differs from that of other species, since they lie 

 parallel to the surface (Fig. 54, A), whereas the larvae of other 

 mosquitoes hang from the surface at an angle (Fig. 54, B). At 

 the posterior end of the body is a short breathing tube which is 

 thrust through the surface film. In about two weeks the 

 full-grown larvae change to pupae (Fig. 55). These must also 

 remain near the surface, since they breathe through two tubes 

 that look like ears and project from the thorax. The pupal 

 stage lasts about four days, and then the adults emerge. 

 The adults are active at night and only the females bite. 

 During the winter mosquitoes hibernate in crevices as do 

 the house flies. 



Enemies of Mosquitoes. Mosquitoes fall a prey to many 

 natural enemies. The adults are devoured by certain night- 

 flying birds, such as the nighthawk, by dragon flies (the so-called 

 mosquito hawks), by spiders and toads, and by bats which fly 

 about at dusk just when the mosquitoes begin to get active. 

 The larvae and pupae are destroyed in countless numbers by 

 insect-eating animals that live in the water, especially by small 

 fish and by the large carnivorous insects, such as water scorpions, 

 water beetles, and water boatmen. But while these enemies 

 certainly decrease the number of mosquitoes, they are not able to 

 prevent them from becoming a pest. 



