2 FIRST LESSONS IN ZOOLOGY 



like its parent. The story i)f an animal's birth, its growth 

 and gradual change or development into a mature or 

 adult individual, is called its lifc-stor}' or lifc-liisiory. 



In the following studies of insect life-histories the 

 growth and development of the insects from hatching to 

 maturity can be readil}' observed in the schoolroom. 

 The particular insects chosen are selected because they 

 can be easily obtained and reared indoors, and because 

 they present especially interesting changes in their de- 

 velopment. But other insect life-histories may be ob- 

 served, cither completely or in part, if it is so desired. 

 Various caterpillars and chrysalids can be kept alive and 

 watched as the}' develop into moths or butterflies, and 

 various grubs that live in the ground can be kept until 

 they become beetles. Flesh-flies xwxy be allowed to lay 

 their eggs on decaying meat, and the hatching of the 

 maggots, their change int(^ brown seed-like pupap, and 

 the final emergence from these of the blue and green flies 

 all carefully noted. 



MO.S(JUITOES 



The eggs and hatching. — Most|uitoes' eggs are usually 

 laid in small blackish masses, which float on the surface 

 of water. (In the case of some species the eggs are laid 

 in groups of only a few, or even deposited singly.) These 

 sooty egg-masses are composed of a single layer of slen- 

 der elongate eggs standing on end and loosely fastened 

 together to form a narrow, irregular, little raft, slighth- 

 concave on the upper surface, and wholl)- utisinkable. 

 They are to be found on small pools of standing water, 

 or in watering-troughs or exposed barrels — wherever in- 

 deed tliere is quiet or stagnant ^\'ater. These e<>"- 

 masses shoukl be brought into the schiMilroom and kept 

 in glass tumblers, witli some of the water on which they 

 are found floating (fig. i). Examine an egg-mass with 



