The genus _Melitæa_, for example, can be characterized by the possession of 7-9 fleshy tubercles bearing hairy spines; the genus _Argynnis_ may be distinguished by always having six hairy unbranched spines on each segment, and the genus _Cethosia_ by two similar spines on each segment; the genus _Vanessa_ shows sometimes as many as seven branched spines; and the genus _Limenitis_ never more than two branched blunt spines on each segment, and so forth. If we go further into details it will be seen that the most closely related imagines, as might indeed have been expected, likewise possess the most nearly allied larvæ, whilst very small differences between the imagines are also generally represented by corresponding differences in the larvæ. Thus, for instance, the genus _Vanessa_ of Fabricius has been divided into several genera by later authors. Of these sub-genera, _Grapta_, Doubl. (containing the European _C.-album_, the American _Fabricii_, _Interrogationis_, _Faunus_, _Comma_, &c.), is distinguished by the fact that the larvæ not only possess branched spines on all the segments with the exception of the prothorax, but these spines are also present on the head; in the genus _Vanessa_ (_sensû strictiori_), Doubl., the head and prothorax are spineless (_e.g._ _V. Urticæ_); in the tropical genus _Junonia_, Hübn., which was also formerly (Godart, 1819[186]) united with _Vanessa_, the larvæ bear branched spines on all the segments, the head and prothorax included. It is possible to go still further and to separate two species of _Vanessa_ as two new genera, although they have hitherto been preserved from this fate even by the systematists most given to “splitting.” This decision is certainly justifiable, simply because these species at present stand quite alone, and the practical necessity of forming a distinct genus does not make itself felt, and this practical necessity moreover frequently comes into conflict with scientific claims: science erects a new genus based on the amount of morphological difference, it being quite immaterial whether one or many species make up this genus; such an excessive subdivision is, however, a hindrance to practical requirements, as the cumbrous array of names thereby becomes still further augmented.