_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 {56}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. {57}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.