Introduction to Animal Morphology. 389 



a ganglion whose nerves end in club-like rods, with 

 fine acoustic hairs. This is placed under the knee on 

 the outside of the front pair of legs in Crickets, or in a 

 shallow depression on the metathorax, close to base 

 of the third pair of limbs, and receiving its nerve from 

 the third thoracic ganglion in Acrididoe. In Locusts 

 it is placed on the front pair of legs, and there is an 

 opening into its cavity. At the base of the haltcrcs 

 of Diptera and at the base of the hind wings of beetles 

 there are areas where the chitinous integument is 

 pierced abundantly by pore-canals, and beneath which 

 are clusters of rod-like nerve endings, like those in 

 other auditory organs, but with no tympanic ring nor 

 membrane.* 



s are absent in cave-dwellers, or those living 



in dark places, but are usually two, compound, ses- 



, lateral, with sometimes accessory cornea-bearing 



ocelli, varying in number: this class of eyes, or none, 



t in larvae as a rule. The compound eyes consist 



of 20-, 50-, 4000 (House-fly), 28,000 (Dragon-fly), hexa- 



gonal, rarely quadrate facets. The organ is stalked in 



Chloeon, Diopsis (Dipteron), and some Strepsiptera 



and Hemiptera, but the stalks are not movable. 



The muscles of insects are grouped into those with, and 

 those without, prolongations from the exoskeleton (tendon) 

 for their insertion ; the first group arc cither conical, \\ilh 



ingle, or pyramidal with a laminated tendon, pennifnrm 



lound (arising 1-y several heads). In tin- larva of 



Cossus liirniperda ll: .- :S muscles in the head ; 1647 



in the : ndziiS in the viscera; l>ut these, which 



arc little mo: divided fasciculi offii capable 



ami / D the antennae of 



LamdHcoi 



