328 



A COURSE ON ZOOLOGY. 



insects is limited almost entirely to the perpetuation 

 of the species ; when the eggs are laid in places most 

 favorable for their development, the life of the insect is 

 ended. 



The arrangement of the mouth varies according to 

 the diet. Masticating insects (coleoptera, orthoptera, 

 etc.) possess, as we have seen in the cockchafer, organs 

 adapted for mastication. In the hymenoptera these or- 



VARIOUS FORMS OF CHRYSALIS. o, orange-tip butterfly ; 6, black-veined white 

 butterfly; c, swallow -tailed butterfly ; d, purple emperor; e, silver- washed 

 fritillary ; /, Duke of Burgundy fritillary. 



gans are modified for sucking or lapping soft substances 

 or liquids ; the lower lip is elongated into a membranous 

 tongue, which accompanies the palps, and the jaws form 

 a bivalve sheath, which constitutes the proboscis. In 

 blood-sucking insects (diptera) the mandibles are modi- 

 fied into sharp lancets, which are capable of penetrating 



