BEETLES 189 



between this state and the normal soft pupa. The pupal state 

 lasts but a short time, from one to three weeks being the usual 

 period. The perfect Insect is at first soft and almost colourless, 

 and it is often some days before it attains its complete coloration 

 and hardness. 



Classification. Owing to the hardness of the skeleton, beetles 

 shrivel but little after death, so that the form and relations of 

 the various sclerites can usually be detected with ease. These 

 sclerites seem to be remarkably constant (except in the case of 

 sexual distinctions) within the limits of each species, and are 

 very useful for the formation of genera and groups of genera : 

 but they vary so much outside the limits mentioned that it is 

 very difficult to make use of them for defining the larger groups. 

 Hence it is not easy to frame accurate definitions of the 

 families, and still less so to arrange these families in more com- 

 prehensive series. The natural difficulty has been much increased 

 by the habit coleopterists have of framing their definitions 

 on what is visible without the aid of dissection. Nevertheless 

 considerable progress has been made. "We are obliged at present 

 to adopt upwards of eighty families ; and we are able to dis- 

 tinguish on positive characters five series; this leaves a large 

 number of forms still unclassified, and these we have here 

 associated as a sixth series, which we have called Coleoptera Poly- 

 morpha. This series corresponds with the two series called in 

 books Clavicornia and Serricornia. As it is admitted to be 

 impossible to define these two series, we think it much better to 

 act accordingly, and to establish for the present a great group 

 that can only be characterised by the fact that its members do 

 not belong to any of the other five series. No doubt a larger 

 knowledge of development, coupled with the advance of com- 

 parative anatomy, will ultimately bring about a better state of 

 affairs. The Strepsiptera, with one family Stylopidae, are only 

 provisionally included among the Coleoptera. These six series 

 are fairly equal as regards extent. Though the Polymorpha 

 includes the larger number of forms, yet a large part of them 

 belong to four great families (Staphylinidae, Buprestidae, Elat- 

 eridae, Malacodermidae), which are easily recognisable, so that 

 the number of unmanageable forms is not really great. Indeed, 

 an acquaintance with the external anatomy of two or three 

 dozen species, selected as typical, would enable a student to classify 



