8 ELEMENTARY LESSONS ON INSECTS 



{hex, six and pons, podos, foot). Their six feet readily dis- 

 tinguish them from other Arthropods. Why we, ourselves, 

 have two feet, and vertebrates generally have four, and 

 insects six and spiders eight, and crustaceans and milli- 

 pedes still more, is not explained, but three pairs are the 

 allotment of this group we are now studying. 



The first segment is called the prothorax (pro, before) 

 and the other two together, being more alike and more closely 

 conjoined, are called the synthorax (syn, together). 



For futher convenience, each segment bears its own 

 name, the second or middle segment being appropriately 

 called the mesothorax (mesos, middle), and third, the meta- 

 thorax (meta, beyond). 



The prothorax bears only a single pair of legs, but meso- 

 thorax and metathorax bear each a pair of wings (in addi- 

 tion to a pair of legs). In the young of some stoneflies on 

 the under side of the thorax will be found tufts or gills, 

 arising from the thin membranes at the joinings of the 

 segments. 



The leg of an insect is built on the following plan: there 

 are two short basal segments, coxa and trochanter, that 

 make attachment to the body and provide for the upward 

 turn; then there are two long segments, femur and tibia, 

 meeting at the knee; then there are three short segments 

 (the number varying from one to five in other insects), 

 composing the foot or tarsus (plural, tarsi). All these names, 

 being borrowed directly from human anatomy, ought to 

 be easy to remember, if we know the names of the bones 



