308 HETEROMERA. 
southwards, the converse being the case in the genus Mordella. Mexico and Central 
America prove to have almost the same number of species as the United States: 
seventy-five in the former, as against seventy-seven in the latter. Of the seventy-five 
here enumerated, forty-one occur in Mexico, thirty-four in Guatemala, and sixteen in 
the State of Panama. Very few species extend from Mexico to Panama, but many 
are common to Mexico and Guatemala; a considerable number seem to be peculiar to 
Western Mexico. Twenty-three species only have been recorded as yet from South 
America——one from Colombia, four from Peru, sixteen from Brazil, and two from 
Chili; but several of the species of Mordella of the older authors belong to it, as 
M. ferruginea, Fabr., from §. America, M. rubida, Er., from Peru, &c. One species 
only has hitherto been described from within our limits. Important sexual characters 
are to be found in many species of Mordellistena, more particularly in the form of the 
apical joint of the maxillary palpi. In I. ephippiata, M. lineatocollis, and M. equi- 
noctialis, and also in some very small species, M. xanthopyga, M. palpalis, M. perexigua, 
&c., this joint is hammer- (or boat-) shaped in the male, and more or less elongate- 
triangular or oblong-ovate in the female: J. ephippiata and its allies agree very nearly 
with the European J. abdominalis, Fabr., a species placed by Emery in his section 
Mordellochroa, though he did not notice the form of the maxillary palpi in the male; 
M. xanthopyga, &c., with the species placed by the same author in his section Tolida. 
The apical joint of the maxillary palpi is often a little longer in the male than in the 
female, in some cases being stouter and more angular, and in others more cultriform, 
in the first-ementioned sex; the second joint in several species is considerably stouter 
in the male than in the female. In the males of WM. distorta and M. curvimana the 
anterior tibiee are broadly dilated and flattened, and the first joint of the anterior tarsi 
is bowed inwards and much elongated. In the male of I. sexmaculata the eight outer 
joints of the antenne are thickened and much elongated, the fourth and fifth being 
equal; in the female of the same species the fourth joint is small and subequal with 
the third, the fifth being more than twice as long as, and very much stouter than, 
the fourth. ‘The number and position of the ridges on the hind tibiz and on one 
or more of the hind tarsal joints is also a very useful character in discriminating the 
numerous species; but American authors have placed far too much reliance upon the 
exact number of these ridges. Amongst a long series of examples of some species an 
additional, often short or rudimentary, ridge (or two) is to be found in advance of the 
others on the tibie or tarsal joints of one or more specimens, the additional ridge (or 
ridges) not always being symmetrical on both legs; in M. murina &c. the ridges vary 
in number from 3-5 on the tibie and first tarsal joint. In a number of species (as in 
many from the United States) the anterior ridge on the hind tibie is obliquely extended 
across their outer face to near the base, this character easily distinguishing several very 
closely allied forms. In two Mexican species undoubtedly belonging to this genus, 
M. fasciculata and M. festiva, the hind tibie have only a subapical ridge (as in 
