﻿192 



COLEOPTERA 



they are placed partially in the thorax. The diminution in 

 number takes place in this case by the amalgamation of the first 

 two abdominal with the last thoracic ganglia. 



Fam. 1. Passalidae. — Labrum large, mobile ; mentum deeply 

 cut out in the middle for the accommodation of the ligula ; the 

 lamellae nf the antenna brought together by the curling up of the 

 antenna. The elytra entirely cover the dorsal surface if the abdo- 

 men. There are four or five hundred species of this family known ; 

 they are usually shining-black, unattractive beetles, of large size, 



*~~J 



fcr-"9 



Fig. 86. — View of one 

 side of meso- an<l 

 m e t a t h o r a x of a 

 Passalid larva from 

 Borneo showing the 

 stridulating organs. 

 a, //, Portions of the 

 metathorax ; c, coxa 

 of 2nd leg ; <l. striate 

 or stridulating area 

 thereon ; e, basal 

 part of femur of 

 middle leg ; /, hairs 

 with chitinous pro- 

 cess at base of each ; 

 g, the diminutive 

 3rd leg modified 

 for scratching the 

 striated area, x 20. 



and are abundant in the decaying wood of tropical forests. They 

 are quite absent from Europe, and there is only one species in 

 the United States of North America. The larvae are very 

 interesting, from the fact that they appear to have only four legs. 

 This arises from the posterior pair being present only as very 

 short processes, the function of which is to scrape striated areas on 

 the preceding pair of legs and so produce sound. In the species 

 figured (Fig. 80) this short leg is a paw-like structure, bearing 

 several hard digits; but in other species it is more simple, and 

 without the digits. The perfect Insect has also sound-producing 

 organs, and Ohaus has suggested the reason why the larvae are 



