INTRODUCTION 19 



lications. Many of these publications are available and will 

 be found to contain an immense store of information, much 

 of it of very practical value, but its greatest utility will be 

 found to rest upon some acquaintance with the general 

 facts of insect life and insect habits. These are so dependent 

 upon certain conditions of structure and development that 

 acquaintance with some of the fundamental biological 

 features of insect life are essential to the most effective 

 utilization. 



Formerly all of the arthropods, that is, all animals with 

 jointed bodies and jointed appendages, were grouped under 

 the head of insects, and even yet this term has a pretty 

 wide application in popular usage, although it is seldom 

 used now to cover as wide a range as formerly. The Arth- 

 ropods, as a whole, include crustaceans, myriapods, arach- 

 nids, hexapods, or^ six-footed insects, and of these the air- 

 breathing forms, all except the crustaceans, are still quite 

 commonly treated as insects. 



The Onychophora is a tropical group including peripatus, 

 the most primitive of tracheate animals, and would on this 

 basis be considered as falling next to the Crustacea. 



The most generalized next to these, the myriapods, might 

 be counted as possessing the greater number of insect-like 

 characters. This group, however, does not include any 

 forms that possess wings, but in the matter of antennse and 

 the tracheal respiration they are closely associated with 

 insects. The members of this group are, for the most part, 

 of comparatively little economic importance. A few of the 

 species included in the group of centipedes {Chilopoda) are 

 poisonous, and in tropical countries are of some importance 

 on this account. The few species that occur in temperate 

 regions have little importance except as they may feed upon 

 other insects which occur under the litter at the surface of 

 the ground. 



One species, the house centipede, a peculiar long-legged 

 creature, which is occasionally found in cellars or around 

 houses, usually where there is some dampness, is, however, 

 of a certain amount of importance because of its feeding 



