i. The first subdivision will include the pupæ, if they may be so

called[563], of insects of the _Aptera_ order, and of the class _Arachnida_: as, lice, _Poduræ_, _Lepismidæ_, centipedes, millipedes, mites, harvest-men, spiders, scorpions, &c. These mostly differ from their larvæ only in that the relative length or number of their legs, the number of the segments of the body in some, or the development of their palpi, more nearly approach the characters of the perfect insect; and in that while in their larva state they have two or more skins to cast, previously to their assumption of the imago, in their pupa state they have but one. In fact, this last circumstance is the only one which, strictly speaking, characterizes the pupæ of this subdivision; as the changes which take place in the number and proportion of the organs are partly produced with each change of the larva's skin. And hence, as it is not easy to ascertain what number of skins a spider, for example, has yet to cast, and as both the larva and pupa differ so little from the perfect insect, it is very difficult to determine in what state insects of this division are. From this difficulty has probably arisen the too great multiplication of species in some of these tribes, particularly the _Arachnida_, the larva and pupa having been mistaken for perfect insects. The pupæ of this subdivision were named by Linné _complete_, from the near resemblance which they bear to the imago.

ii. The second subdivision will include the pupæ of the _Dermaptera_, _Orthoptera_ and _Hemiptera_ orders, with few exceptions; as likewise the _Libellulina_, _Ephemerina_, and _Termitina_? amongst the _Neuroptera_: including the well-known tribes of earwigs, cockroaches, crickets, grasshoppers, locusts, lanthorn-flies, froghoppers (_Cicada_ L.), bugs, plant-lice, dragon-flies, day-flies, white ants, &c. Of these, as in the former subdivision, the pupæ are equally capable of eating and moving with the larvæ, which they resemble, except in having the rudiments of wings, or of wings and elytra. The pupæ of the three orders first enumerated differ from those of the _Neuroptera_ in resembling the perfect insect in most instances, both as to shape and the organs for taking their food; and in all other respects, except in not having their wings and elytra fully developed[564]. The resemblance of the pupæ of the _Libellulina_ and _Ephemerina_ to the perfect insects is more distant, and the above organs in the two states are very dissimilar; for the pupæ of the former are furnished with a prehensory mask similar to that of the larvæ before described[565], which the perfect insect has not; and those of the latter with the usual oral organs of masticating insects, of which the imago has scarcely the rudiments.

I have applied the term _rudiments_ to the wings and elytra in this state, not in a strict sense, but merely to denote their appearance; for in fact the wings, &c. are complete, but only folded up longitudinally and transversely, and inclosed in membranous cases, which when the last change takes place remain attached to the puparium or pupa-case. The tegmina or hemelytra in this state usually cover the wings, and the upper wings the under; but in the _Libellulina_ both are usually visible. Though commonly very small compared with the instruments of flight in the perfect insect, some of these rudiments, contrasted with the majority, are of considerable magnitude. This is the case with those of some species of _Chermes_, as we learn from De Geer[566].

II. The second grand division comprises by far the largest number of pupæ: those of all _coleopterous_, _strepsipterous_, _lepidopterous_, _hymenopterous_, _dipterous_, and _aphanipterous_, and by far the majority of _neuropterous_ insects, as well as the _hemipterous_ genus _Aleyrodes_, and one sex of _Coccus_ of the same order. These pupæ, however, though agreeing in the circumstance of being unlike the larvæ from which they proceed, differ from each other in several respects, and require to be divided into three great sections, as under:--

i. Those pupæ in which the _parts_ of the future insect, being folded up under a membranous skin closely applying to each, are distinctly _visible_. To this head belong generally, the pupæ of _coleopterous_[567] and _hymenopterous_ insects; those of the _neuropterous_ genera _Myrmeleon_ and _Hemerobius_, &c.; the _Trichoptera_; amongst the _Diptera_, _Culex_, _Tipula_ L., _Tabanus_, _Bombylius_, &c.; and that of the flea (_Pulex_). These were the _incomplete_ pupæ of Linné.

ii. Those pupæ in which the _parts_ of the future insect, being folded up under a harder skin, are _less_ distinctly _discoverable_. To this subdivision belong the pupæ of all _Lepidoptera_, and of them alone. These are what Linné termed _obtected_ pupæ.