204 HETEROMERA. 
known from America north of Mexico, two from the northern part of South America, 
and one from the Antilles*. Sixteen are now recorded from Central America, eight of 
which appear to be peculiar to Mexico. We follow, as nearly as possible, the arrange- 
ment adopted by Dr. Horn in his excellent monograph of the North-American species 
(op. cit.). As this author remarks, the elytral markings are often variable and not 
always to be relied upon as specific characters unless supported by other marks of 
distinction. Important characters exist in some species in the form of the apices of 
the elytra (not only in the male but in the female also) and also in that of the fifth 
ventral segment (in the male). We have,unfortunately, very insufficient material of 
several of the species (more particularly of the Mexican ones), in some cases one sex 
only being represented ; so that we are unable to describe the sexual marks of distinc- 
tion in WV. opacus, N. ventralis, N. fraternus, N. truncatipennis, N. crucifer, &c. 
Various Nearctic and Palearctic species (NV. monoceros, Linn., N. anchora, Hentz, 
&c.) have the sutural angles of the elytra in the male retracted and the apices obliquely 
truncate and more or less spinous externally ; none of the Central-American species of 
which the males are known possess this peculiarity. MV. acuminatus is remarkable from 
having the apices of the elytra subacuminate in both sexes. 
These insects are chiefly found in sandy places, not only upon the ground, but upon 
low herbage and bushes. 
The Central-American species may be grouped thus :— 
Elytra with fine or moderately coarse decumbent pubescence, sometimes 
with scattered, longer, serially arranged, decumbent or erect hairs ; 
apices conjointly rounded in both sexes, or separately rounded in the 
male, or truncate in the female. 
Surface unicolorous black and opaque (the prothorax, the horn 
excepted, reddish-testaceous) ; post-humeral depression obsolete . Species 1, 2. 
Surface fasciate. 
Post-humeral depression deep in both sexes; surface shining or 
slightly shming . . . . . - os. . . « . « Species 3, 4. 
Post-humeral depression moderately deep surfate opaque. . . . Species 5 
Post-humeral depression shallow; surface shining . . . . . Species 6-9. 
Elytra with fine decumbent pubescence and long, scattered, erect hairs , 
post-humeral depression deep in both sexes; apices subacuminate . Species 10. 
Elytra with coarse decumbent pubescence and numerous long erect hairs ; 
post-humeral depression more or less distinct; apices conjointly 
rounded or slightly produced . . . . . . . . 2...) . Species 11-16. 
* N. bipunctatus, Chevr. Bull. Soc. Ent. Fr. (5) vii. p. ix (=. krugi, Qued. Berl. ent. Zeitschr. xxx. p. 121), 
from Puerto Rico. 
