278 



METAZOAN PHYLA 



parts. In suctorial insects (Fig. 183) 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. This 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. It is inter- 

 esting to note that many insects that have sucking mouth parts in their 

 adult stage have the chewing type in their larval stage. This is inter- 

 preted by most authorities to indicate that the chewing type is the more 

 primitive. 



Ocellus 



Compounc^ 

 eyes - 



Antennae 



Maxillary 

 palpus ' 



Labrum^ 

 epipharynx 



Hypopharynx, 



Mandibles 

 Maxi/lae 



Labi urn- 



-Hypopharynx 

 p^ 3? Souton 



Fig. 183. — Suctorial mouth parts, ^.honeybee. Head viewed from in front. {From 

 Herms, "Medical 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. 182 and 183). 



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. 184). 

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

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



