.30 



LIFE HISTORY AT^D HABITS. 



remain unwing'ed ; whilst the males pass through a transformation and 

 emerg-e as tiny flying insects with but one pair of wings (fig. 43). 

 These are instances of incomplete development and are not to be confused 

 with the differences between the sexes discussed in a later section. 



Hibernation and Broods. 



Insects are unable to live and breed continuously throughout the year, 

 except in places Avith a general uniformity of conditions throughout the 

 whole year. In the plains of India, three causes combine to check the 



Fig. 41. 

 The Mice Leaf Bag-ivorm. a, male moth ; h, female adult, an imperfectly developed 

 moth ; c, caterpillar in case of leaves, 



continuous growth and breeding of insect life ; these are cold, excessive 

 dry heat and absence of food. 



A great number of insects are inactive in the cold weather and are 

 then said to hibernate ; as the temperature falls these insects become torpid, 

 remaining inactive until the temperature rises. Hibernation is not uni- 

 versal ; many pests are active in the cold season, attacking the rabi crops ; 

 others emerge from hibernation in time to attack the ripening crops. J'he 

 occurrence and period of hibernation depend largely upon climatic condi- 

 tions ; the temperature does not fall evenly throughout the plains of India, 

 and a species that hibernates in one locality may not do so in another. 

 Much has yet to be learnt of hibernation ; few insects are active in the 

 cold weather in dry cold localities; few hibernate in warmer, damper 



