LESSONS IN ZOOLOGY. 279 



As soon as the insect is complete, the sexes meet, and soon 

 afterward the male, no longer useful, dies; the female lays her 

 eggs in or near some food supply, then dies. For most insects 

 this period occurs in the late summer or early antumn, so that 

 the species is represented during the winter by eggs alone. Some- 

 times the winter is passed in the pupal stage, and in some cases 

 in the larval stage. Insects may brood two, three or more times 

 in one season, but in general, insects are annuals. Sometimes 

 the larva live for many years, as in the case of the seventeen-year 

 cicadia. 



The insect-fauna of a locality comprise all the insect forms 

 found in it. The limits of a fauna are usually determined by 

 temperature or some natural barrier, as the ocean or a high 

 range of mountains, etc. Insects may be distributed ,by the 

 wind, by the agency of birds, or other animals, or of man. The 

 life of an insect is short and active, and has but a single purpose, 

 and yet many insects are subject to disease, for the most part 

 diseases due to parasitic plants or animals. The honey bee, the 

 silkworm, and the house fly are each subject to fungoid diseases. 



There are so many different kinds of insects that the names of 

 the principal groups with some distinguishing characteristics may 

 be helpful. The lowest group of insects are the Thysanura, includ- 

 ing wingless insects, with rudimentary mouth parts and setiform 

 anal filaments which of ten serve as springing organs, so that they 

 are sometimes known as spring-tails. They develop without 

 metamorphosis, and seem to be the most ancient insects as well 

 as the lowest. 



The Orthoptersi. The insects of this order including the grass- 

 hoppers, crickets, etc., have biting jaws, and pass through an 

 incomplete metamorphosis. There is no resting stage ; the newly 

 hatched larva differs from the adult only in size, and the pupa is 

 characterized by rudimentary wings. As a rule they are vora- 

 cious eaters and make sounds of piercing shrillness. 



Some of the largest insects are members of this group, and the 

 grasshopper is one of the best subjects for investigation. Have 

 several individuals in different stages of development confined 



