“It appears to us that Latreille’s three divisions, taken from Linnæus--_Diurnal_, _Crepuscular_, and _Nocturnal_--are too inaccurate to be retained, especially the crepuscular section. The denomination _Diurnal_ not only applies to all the known kinds of day butterflies, but also to an almost infinite number of others forming a part of the two other divisions, such as _Macroglossa_, _Zygenides_, _Castniariæ, gocerides_, &c. That of _Crepuscular_ is adapted more or less to some sphinges, but by no means to the _Zygenides_, which fly only in the heat of the sun. Finally, the term _Nocturnal_ is not more properly applicable to all the species, since many belonging to this section appear only during the day. In order to avoid these improper denominations, we have substituted for the word _Diurnal_, that of _Rhopaloceres_, proposed by M. Dumeril. Being unable to perceive limits between the _Crepuscular_ and _Nocturnal_ divisions of Latreille, we have united those two great sections under the name of _Heteroceres_. In our method, therefore, the lepidoptera are divided into two grand legions, _Rhopaloceres_ and _Heteroceres_[27].” Dr. Boisduval then proceeds to explain that the first of these divisions is characterised by antennæ thickening to a club at the extremity; and the second, by having these organs variously shaped; this indeed is implied by the words themselves. The first division is subdivided into three sections, according to the manner in which the caterpillars transform themselves into chrysalides. Such as undergo this change by attaching themselves by the tail and a band round the middle, form the first division, named _Succincti_; such as are suspended by the tail only, the second, _Penduli_; while those which form a cocoon by rolling leaves together, compose the third division, termed _Involuti_. Each of these three sections is then divided into _tribes_, according to characters derived from the caterpillars and the perfect insect. Among those furnished by the latter, the most important are considered to be the number of ambulatory legs and the form of the palpi. The genera are characterised by the form of the caterpillar and chrysalis, by the dispositions of the nervures of the wings, the form of the antennæ, legs, palpi, thorax, &c. of the perfect insect. GENUS ORNITHOPTERA.