BACTROCERUS.—MACRATRIA. 195 
apical joint of the antenne (in B. concolor equal to the preceding four joints united), 
more distinctly emarginate eyes, the rather feeble and not abrupt anterior constriction 
of the thorax, and fasciculate elytral pubescence. The apical joint of the maxillary 
palpi is broad and subtriangular, the apical side rather longer than the inner side. 
The colour of the pubescence is variable. The specimens obtained exhibit a very 
great disparity in size, the males (as in some Cidemeride) being very much smaller 
than the females. 
MACRATRIA. 
Macratria, Newman, Ent. Mag. v. p. 377 (1838) ; Lacordaire, Gen. Col. v. p. 579; Gemminger & 
Harold, Cat. Col. vii. p. 2082. 
Macrarthria, Erichson, Archiv fiir Naturg. 1840, 2, p. 307. 
Macrarthrius, La Ferté, Monogr. Anthic. p. 11 (1848). 
Twenty-nine * species of this very widely distributed genus have been described, 
chiefly from the warmer parts of the globe; eleven are here recorded from Central 
America. These latter are so closely allied that they are exceedingly difficult to 
discriminate; this cannot always be satisfactorily done till the sex of the individual 
under examination is ascertained. In some species the apical joint of the antenne is 
much longer in the male than in the female, while in others it is of equal length in 
both sexes. The form of the terminal segments (dorsal and ventral) of the hind body 
often affords a good distinguishing character, more especially in the female sex. In 
the male the fifth segment (dorsal and ventral) is usually more or less broadly truncate 
(also emarginate in some species) at the apex; in the female it is longer, with the apex 
of the dorsal portion rounded or produced in the middle and at the sides. In the 
female of UM. incana the apex of the fifth dorsal segment} has not only a long 
horizontal projecting piece in the middle (resembling the cedeagus of the male), but 
the sides are also angularly produced. In the female of WM. princeps the fifth dorsal 
segment is divided down the centre, and beyond this a long projecting piece from the 
middle of the sixth segment (similar to that of the fifth in MW. incana &c.) is visible. 
Our material is not sufficient to enable me to examine these parts in all the different 
species; I. princeps exhibits, however, a very different structure from that of the 
other members of the genus. The importance of the sexual characters in this genus 
has been almost entirely overlooked by recent authors, and in the descriptions of many 
of the eastern Macratrie no mention whatever is made of the sex of the, individuals 
described; the males of some of these latter have the anterior tibie dilated. As in 
Eurygenius and Bactrocerus, the eyes are clothed with short hairs. The following table 
will assist in the identification of the Central- American, ‘forms: — 
* M. gigas, Mars., from Japan, has nothing to do with Macratria: it is a typical Stereopalpus. 
+ The corresponding segment to the fifth ventral: it is really the sixth; an additional segment being visible 
on the dorsal side at the base. 
2CC 2 
