CLASS INSECT A 



273 



parts. In suctorial insects (Fig. 172) a proboscis is present which 

 can be thrust into the tissues of plants or other animals or which 

 may be used in merely taking liquid from a surface. ''J'his proboscis 

 is not developed from the same parts in different insects. In the bee 

 it is formed by the maxillae and the labial palpi; in the mosquito, by 

 the labrum and epipharynx; in the butterflies and moths, by the maxillae; 

 and in other insects, in still different fashions. The adults of some 

 insects have only rudimentary mouth parts and are incapable of feeding; 

 this is true, for instance, of our large native silkworm moths. 



Ocellus 



Compound 

 eyes - 



Antennae 



Maxillary 

 palpus 



La brum + 

 epipharynx 



Hypopharynx, 



Mandibles 

 Maxi/lae 



Labium 



■Hypopharynx 

 'oufon 



Fig. 172. — Suctorial mouth parts. .4, honeybee. Head viewed from in front. {From 

 Herms, '^ Aledical and Veterinary Entomology," by the courtesy of The Macmillan Company.) 

 B, head of a female mosquito, viewed from side with mouth parts separated. (From 

 Matheson, '^Handbook of the Mosquitoes of North America," by permission of the publisher: 

 Charles C. Thomas.) Both greatly enlarged. 



Insects generally have a pair of compound eyes, although these differ 

 greatly in size in different types or may be absent. Some of them also 

 possess simple eyes, or ocelli, placed between and in front of the compound 

 eyes (Figs. 171 and 172). 



Each of the metameres of the thorax bears a pair of legs and each of 

 the two posterior ones, as a rule, a pair of wings. The legs of insects 

 are variously modified and used in a great variety of ways (Fig. 173). 

 Running insects generally possess long and slender legs, the three pairs 

 being equally well-developed. Jumping insects like the locusts and 

 crickets have extremely long hind legs, and the joint known as the femur 

 is very large. Insects living in the water may have hind legs modified 



