INSECT ECOLOGY 377 



the caterpillars are almost starved, some will die, and there will result 

 many more male adults than female. Dr. C. V. Riley explained this 

 long ago, by pointing out the fact that female caterpillars require a 

 longer time for growth than males (having sometimes one more molt 

 than the males); so that conditions of starvation would kill chiefly 

 female caterpillars, that had not completed their growth, and affect 

 male caterpillars less. T. H. Morgan, in a discussion of the subject, 

 adopts this view, and points out the fact that the sex of the caterpillar 

 is determined before the egg is laid; furthermore, that an excess of food 

 does not cause an excess of females. 



Longevity .The duration of life is evidently related to food. 

 Insects cannot live long, if active, without food; and activity is corre- 

 lated with the amount of food utilized. 



Females live longer than males, with some exceptions, particularly 

 if they have not laid their eggs, and frequently possess an ample supply 

 of reserve food accumulated by the larva, as in the case of many moths, 

 particularly such as do not themselves feed as adults (silkworm moth) . 



With cotton boll weevils after emergence from hibernation, unfed 

 beetles of both sexes were found to live ten days, and fed beetles, 

 twenty-five days. (Hinds and Yothers.) 



A queen honey bee, constantly fed with highly nutritious food, 

 may live more than four years; a queen ant, fifteen years (one instance). 

 On the other hand, the Hessian fly, which does not feed and has 

 little reserve nutriment, lives only from one day (males) to four days 

 (females). 



A remarkable instance of longevity under starvation conditions is 

 given by J. E. Wodsedalek. Finding that larvae of the common museum 

 beetle, Trogoderma tarsale, would live a long time without food, molting 

 meanwhile but not eating the cast skins, he tested their longevity by 

 keeping them individually in glass vials without food. The larvae 

 gradually decreased in size to almost their length at hatching, but were 

 surprisingly tenacious of life. Newly hatched larvae that had never 

 eaten lived four months without food; quarter-grown larvae, fourteen 

 months; half-grown larvae, three years; three-quarters-grown larvae, 

 four years; and full grown individuals, from four years to five years, 

 one month and twenty-nine days (one larva). If stunted specimens 

 were given food they began to grow again, and could again be reduced 

 in size by a second period of starvation. By alternate periods of feasting 

 and fasting, larvae were three times brought to their maximum size 

 and three times reduced to the minimum size. 



