394 INSECTA. 



exposed, crustaceous, and transversal; the mandibles strong and 

 much dentated, but without any very remarkable sexual difference; 

 the maxillae entirely corneous, with at least two strong teeth; the 

 ligula equally corneous or very hard, situated in a superior emargi- 

 nation of the mentum, and terminated by three points; the abdomen 

 pediculated, presenting the scutellum above, and separated from 

 the thorax by a strangulation of considerable interval. They form 

 the genus 



Passaltjs, Fab. 

 Restricted by M. Mac Leay to those species in which the club of the anten- 

 nae consists of but three joints, where the labrum forms a transversal square, 

 and the maxillse have three strong terminal teeth, and two on the inner 

 side in place of the anterior lobe. 



These Insects are foreign to Europe, and as it would appear, to Africa, 

 being chiefly found in the eastern parts of Asia, and particularly in America. 

 Madame Merian says, that the larva of the species figured by her lives on 

 the roots of the sweet potato. The perfect Insect is not uncommon in the 

 sugar-houses. 



In the second general section of the Coleoptera, or the Hetero- 

 MEEA, we find five joints in the four first tarsi, and one less in the 

 two last. They all feed on vegetable matters. 



In some, where the elytra are generally solid and hard, and the 

 hooks of the tarsi are almost always simple, the head is ovoid or 

 oval, susceptible of being received posteriorly into the thorax, or 

 sometimes narrowed behind, but not abruptly, and without a neck 

 at its base. Many of these Heteromera avoid the light. This divi- 

 sion will comprise the three following families. 



FAMILY I. 



MELASOMA. 



This family consists of unmixed black or cinereous coloured In- 

 sects, (from which is derived the name of the division,) mostly 

 apterous, and frequently v^ith soldered elytra. Their antennse, 

 entirely or partly granose, almost of equal thickness throughout or 

 slightly inflated at the extremity, and the third joint wholly elongated, 

 are inserted under the projecting edges of the head. The mandi- 

 bles are bifid or emarginated at the extremity; the inner side of their 



