CHALCOLEPIDIUS. 273 



with two very different forms of scales — one minute and usually opalescent or metallic, 

 the other larger, more elongate, and opaque, white, luteous, or fulvous, these latter 

 often forming a marginal vitta on the thorax and elytra ; the larger scales seem to be 

 loosely attached and easily abraded. Viewed under a microscope," with a J-inch 

 objective, the large scales are strongly transversely strigose, as well as longitudinally 

 striated, the small ones longitudinally striated only. Some of the species vary greatly 

 in the colour of the scales, and in one, at least, G. mexicanus, the males have the 

 whitish scales almost obliterated above. The elytra usually have the marginal carina 

 more or less deflexed anteriorly, becoming indistinct or almost obsolete in front ; but 

 in several species (G. desmaresti, &c.) it is distinct to the base. The males of many 

 of the species are of extraordinary rarity; they may always be known from the 

 females by having the fifth ventral segment rounded at the apex, this segment being 

 broadly truncate and ciliate in the females. In addition to this, other sexual characters 

 are in most cases to be found in the clothing or armature of the tibiae or tarsi, and 

 sometimes in the form of the antennae. 



These insects form a characteristic feature in the fauna of the forest-region of 

 Central and South America. They are found crawling on fallen decaying trees, in 

 which the earlier stages are passed ; some of the species, 0. lacordairei, G. exquisitus, 

 G. silbermanni, &c, are often rather abundant where they occur. 



The metamorphoses of C. approximatus (zonatus, Duges) have been described and 

 figured by Dr. E. Duges. 



The following table is added to assist in the identification of the Central-American 

 species ; but it must be remembered that the males of G. forreri, G. inops, G. murinus, 

 C.jansoni, G. mniszechi, G. lenzi, G. behrensi, and G. tenuis are unknown or undescribed, 

 and that no specimens of either sex of G. lenzi, C. behrensi, G. mniszechi, and C. inops 

 are available for examination : — 



1. Scutellum horizontal, subtriangular or obcordate, usually more or less bilobed 

 in front. 



a. Antenna? serrate in both sexes ; apical joint of each tarsus and the anterior, 

 or the anterior and intermediate, tibia? (except in C. webbi) ciliate in 



the <?*. 

 a 1 . Propleuraa grooved or plicate in front for the reception of the basal 

 joints of the antennas. 

 a". Antennse with the third joint as long as the fourth. 



a'". Prothorax and elytra with a marginal band of fulvous, luteous, 

 or whitish scales. 

 a\ Scales on the epipleurse and under surface similar. 



a 5 . Marginal bands on the prothorax extending to the base. 

 a\ Elytra with a line of elongate fulvous or whitish scales on 



each of the striaa bonplandi. 



* In the species of which the males are known. 



biol. cente.-amer., Coleopt, Vol. III. Pt. 1, 'November 1894. 2 N" 



