STRUCTURE, GROWTH AND ECONOMICS OF INSECTS 



II 



segments are fine hairs, connected below with nucleated nerve cells, 

 which are believed to be tactile hairs. There are too in some cases pits 

 or oval depressions, also connected with a nerve cell, which are thought 

 to be gustatory organs. Other pits situated in patches at the lower end 

 of the segments are beheved to be auditory organs. 



Eyes. — The eyes of insects are of three kinds: simple, compound and 

 agglomerate. The simple eyes or ocelli appear externally as a single 

 convex lens, and are borne by the most primitive insects such as the 

 Collembola, all eyed larvae, and in the 

 adults of most of the winged insects. In 

 winged forms there are usually three, supple- 

 mentary to the compound eyes, and borne 

 on the vertex or on the front, arranged 

 generally in a triangle. The agglomerate 

 eye is a compound eye in which the facets 

 are not fused but well separated from each 

 other, e.g., male Coccids. 



Organs of Hearing.- — Several kinds of 

 auditory organs occur in insects and these 

 are variously located. In locusts they are 

 tympanic membranes, located on the base 

 of the abdomen; in the katydids and 

 crickets on the tibiae of the fore legs. In 

 the mosquitoes and many other groups 

 certain sensitive hairs on the antennae serve 

 to take up and transmit sound waves. 



Organs of Smell.— These organs are butterfly (Vanessa), a., 



° ^ , tennse; /., labial palpi; p., 



variously located — on the antennae in flesh boscis. (After Foisom.) 

 flies, ants, bees and wasps, some moths and 



beetles; on the maxillary and labial palpi in Perla and Silpha; and 

 on the cerci in the cockroach and some Orthoptera. 



Organs of Taste. — Taste organs are also variously located — on 

 the hypopharynx in the honey bee, on the epipharynx of most biting 

 insects, and on the maxillary palpi in wasps. 



All sense organs consist essentially of the following parts: (i) a 

 nerve of the central nervous system communicating with (2) one or 

 two modified hypodermal cells, and (3) external supporting or accessory 

 structures such as setce, tubercles or pits. 



Fig. I 5 



-Head 



of a 

 An- 

 pro- 



