208 MODERN CLASSIFICATION OF INSECTS. 



in entomological geography dependent, as Mr. MacLeay observes, 

 upon the want in the Australasian continent of all large herbivorous 

 Mammalia, except of the marsupial kind. Some of the species feed 

 upon vegetable matter in a decaying state, especially such as are found 

 upon the sea coast (Psammodius), and in w^hich the maxillae are of a 

 more horny consistence, thus leading naturally to the following 

 family. 



From the Geotrupidae and Trogidae these insects are distinguished 

 by the structure of the mandibles, which, together with the labrum, 

 are concealed beneath the large produced clypeus, and the short 

 glabrous palpi. 



The fourth family, Trogidae of MacLeay, is a family of but 

 moderate extent, although very generally dispersed over the surface 

 of the globe (^fig- 20. 19. Trox sabulosus) ; and is distinguished by hav- 

 ing the labrum coriaceous, and exserted ; the antennae 9 or 10-jointed; 

 the club 3-jointed, the lamellae being apart ; the labium is entirely 

 concealed by the mentum (^fig. 20. 22.) ; the mandibles are horny, 

 and sometimes toothed {fig. 20. 20.) ; the maxillae are terminated 

 by two lobes, often corneous and toothed {fig. 20. 21.) ; the body is 

 ovate and gibbose, the elytra being inflexed at the sides ; the scu- 

 tellum is distinct, and the anterior tibiae are often but imperfectly 

 toothed on the outside ; the head is deflexed ; the thorax short, and 

 transverse, posteriorly sinuated, v/ith the anterior angles advanced. 

 Some of the species are destitute of wings, — a peculiarity not observed 

 in any other of the Linnaean Scarabaei ; the elytra are very rugose, 

 and often clothed with patches of short thick hairs or scales. 



This family is related to the Geotrupidae (with which Latreille has, 

 indeed, united it, under the name of Arenicoli), in the exserted 

 labrum and horny jaws; as well as to the Aphodiidae, as above noticed. 

 From these groups, however, they are sufficiently removed both in 

 their structure and habits. They also bear a certain resemblance to 

 some of the Histeridae. 



These insects produce a creaking kind of noise by alternately 

 rubbing the anterior part of the mesothorax against the prothoracic 

 cavity, or more probably the extremity of the abdomen against the 

 elytra. They also possess the habit of counterfeiting death when 

 alarmed, in the same manner as the Histeridte. 



