INSECTS OF THE HOUSEHOLD 65 



Stages, known as ''wrigglers," in the water, and in from 

 seven to fourteen clays, according to weather, emerge as 

 adult mosquitoes. A female may lay from 200 to 400 

 eggs. A good example in arithmetic is the following: 



Suppose a mosquito lays 200 eggs, one-half of which 

 hatch females, and these each lay 200 eggs, and so on, 

 calling the time for a generation ten days ; how many 

 mosquitoes would there be after 180 days, i.e., in the 



eighteenth gen erat i on? ™ -, 



The answer is 2,000,000,- 

 000,000,000,000,000,000,- 

 000,000,000,000,000, one- 

 half of which may be 

 males. This is, accord- 

 ing to Dr. Howard, about 

 the minimal period in 

 which a generation can 



mature. What would the I^"^- 21. Female anopheles Mosquito 

 result be if the period were (^^^"^ Photograph by the Author) 



twenty days .? thirty days } Eggs might be collected and 

 reared and the actual time ascertained by the class. 



In one month a single female mosquito may thus give 

 rise to from 1,010,100 to 2,020,000 female mosquitoes, 

 — quite enough to stock a good-sized city. 



Lessons on mosquitoes may be undertaken at any sea- 

 son of the year, but are especially valuable after warm 

 weather begins in spring, — April or May for most parts 

 of this country. A lesson or two in winter will prove 

 instructive in discovering how mosquitoes pass this sea- 

 son. The children should then be asked to seek for 

 specimens in stable and house cellars. 



