Insects.—The butterflies of various parts of Central America and Mexico, having been largely collected, offer us some valuable evidence as to the relations of this sub-region. Their general character is wholly Neotropical, about one half of the South American genera being found here. There are also a few peculiar genera, as, Drucina (Satyridæ); Microtia (Nymphalidæ); Eumæus (Lycænidæ); and Eucheira (Pieridæ). Clothilda (Nymphalidæ) is confined to this sub-region and the Antilles. The majority of the genera range over the whole sub-region from Panama to Mexico, but there are a considerable number, comprising many of the most characteristic South American forms, which do not pass north of Costa Rica or Nicaragua. Such are Lycorea, Ituna, Thyridia, Callithomia, Oleria and Ceratina,—all characteristic South American groups of Danaidæ; Pronophila and Dynastor (Satyridæ); Protogonius, Pycina, Prepona, Nica, Ectima and Colænis (Nymphalidæ); Eurybia and Methonella (Nemeobiidæ); Hades, and Panthemos (Erycinidæ).
Coleoptera.—These present some interesting features, but owing to their vast number only a few of the more important families can be noticed.
Cicindelidæ.—The only specially Neotropical genera recorded as occurring in this sub-region, are Ctenostoma and Hiresia, both reaching Mexico.
Carabidæ.—Several genera are peculiar. Molobrus is found in all parts of the sub-region, while Onychopterygia, Phymatocephalus, and Anisotarsus are Mexican only. There are about 20 South American genera, most of which extend to Mexico, and include such characteristic Neotropical forms as Agra, Callida, Coptodera, Pachyteles, Ardistomus, Aspidoglossa, Stenocrepis, and Pelecium.
Lucanidæ.—Of this important family there is, strange to say, not a single species recorded in Gemminger and Harold's catalogue up to 1868! It is almost impossible that they can be really absent; yet their place seems to he, to some extent, supplied by an unusual development of the allied Passalidæ, of which there are five South American and six peculiar genera.
Cetoniidæ.—All the larger South American genera extend to Mexico, which country possesses 3 peculiar forms, Ischnoscelis, Psilocnemis, and Dialithus; while Trigonopeltastes is characteristic, having 4 Mexican, 1 Brazilian, and 1 North American species.
Buprestidæ.—In this family there are no peculiar genera. All the large South American groups are absent, the only important and characteristic genus being Stenogaster.
Longicorns.—This important group is largely developed, the country being well adapted to them; and their distribution presents some features of interest.
In the Prionidæ there are 6 peculiar genera, the largest being Holonotus with 3 species; two others, Derotrachus and Mallaspis, are characteristic; 3 more are common to South America, and 1 to Cuba. The Cerambycidæ are much more numerous, and there are 24 peculiar genera, the most important being Sphenothecus, Entomosterna, and Cyphosterna; while Crioprosopus and Metaleptus are characteristic of the sub-region, although extending into South America; about 12 Neotropical genera extend to Mexico or Guatemala, while 12 more stop short, as far as yet known, at Nicaragua. Lamiidæ have a very similar distribution; 13 genera are peculiar, the most important being Monilema, Hamatoderus, and Carneades, while Phæa and Lagochirus are characteristic. About sixteen typical Neotropical genera extend to Mexico, and 15 more only reach Nicaragua, among which are such important genera as Anisopus, Lepturgus, and Callia.
The land-shells are not sufficiently known to furnish any corresponding results. They are however mostly of South American genera, and have comparatively little affinity for those of the Antilles.