PHYLUM ARTHROPODA — CLASS INSECTA 



303 



insects. The feelers function in many ways; in some insects they 

 are tactile ; in others they are respiratory or olfactory, or auditory, 

 or may be used to hold the female during copulation. Antennae are 

 useful structures in the classification of insects. 



26 V,' 

 Z7 28 



Fig. 172. — The external features of a grasshopper. 1, maxillary palp; 2, 

 mandible ; 3, labrum ; i, clypeus ; 5, frons ; 6, compound eye ; 7, ocellus ; 8, vertex ; 

 9, antenna; 10, gena : 11, pronotum ; 12, wing, mesothoracic ; 13, spiracle, thoracic; 

 IJi, spiracle, first abdominal segment; 15, auditory apparatus; 16, wing, meta- 

 thoracic ; n, supra-anal plate; 18, podical plate; 19, cercus ; 20, ovipositor; 21, 

 labial palp; 22, femur, prothoracic leg; 23, coxa, mesothoracic leg; 2i, trochanter; 

 25, femur; 26, tibia; 27, tarsus; 28, femur, metatlioracic leg; 29, spiracle; 30, 

 sternum ; 31, tergum. (After Turtox key card, courtesy General Biological Supply 

 House. ) 



Fig. 173. — Detail of ommatidia, magnified. (From White, General Biology, pub- 

 lished by The C. V. Mosby Company.) 



The mouth parts are chitinous structures and are represented in 

 the insects by two distinct types: mandibulate or biting, and suc- 

 torial or sucking mouths. Some of the insect orders which possess 

 mandibulate mouth parts are Coleoptera, Odonata, Neuroptera, 



