3*4 



Handbook of Nature-Study 



through them the air passes into the insect's body. The number 

 of spiracles varies greatly in different insects. There is, however, 

 never more than one pair on a single segment of the body, and they do 

 not occur on the head. The spiracles, or breathing pores, lead into a 

 system of air tubes which are called tracheae (tra'-ke-ee), which permeate 

 the insect's body and thus carry the air to every smallest part of its 

 anatomy. The blood of the insect bathes these thin-walled air tubes 

 and thus becomes purified, just as our blood becomes purified by bathing 

 the air tubes of our lungs. Thus, although the insects do not have 

 localized breathing organs, like our lungs, they have, if the expression 

 may be permitted, lungs in every part of their little bodies. 



"TViorax 



Prop leg 



True leg's 



- \ x ' 



Pro leg-s 



Breathing' pores 



The sphinx caterpillar, with the parts of the external anatomy named. 



Summary of Structure of an Insect 



Antennas. 

 Compound eyes. 

 Simple eyes or ocelli. 



Labrum, or upper lip. 



Mandibles, or upper jaws. 



Head 



Mouth-parts 



Maxillae, or lower jaws, and maxillary 



palpi. 



Labium and labial palpi. 

 Prothorax and first pair of legs. 



Mesothorax and 

 Metathorax and 



f second . pair of legs. 

 [ first pair of wings. 



{ 



Leg 



Thorax 



I 



Two small segments called 



coxa and trochanter. 

 Femur. 

 Tibia. 



Tarsus and claws, 

 ears (in locusts only). 

 Abdomen The abdomen ben rq spiracles. 



, ovipositor. 

 -Manual for the Study of Insects and Insect Life, Comstock . 



