102 ENTOMOLOGICAL SOCIETY 



THE COLEOPTERA. 



The Coleoptera will be described before the Euplexoptera 

 in order to bring out more clearly the points by which the 

 latter resemble in some cases the Orthoptera and in others the 

 Coleoptera. 



The microtlwrax is represented in many beetles but at best 

 is poorly developed, consisting of one or two small sclerites on 

 each side of the neck as in Acridiidge. The labium is always 

 solidly attached to the head, and the cranial walls are closed 

 behind the submentum either by a gular sclerite or by an ap- 

 proximation of the lateral parts. The former condition is 

 probably the original one in beetles, for in the latter case rudi- 

 ments of the gula are present in some families. 



The prothorax is large and its component sclerites when 

 indistinguishable are so through fusion with one another and 

 not through reduction. It is hence probable that the original 

 beetles had the prothoracic pleurites as well developed as those 

 of the succeeding two segments. The Coleoptera thus differ 

 from the Orthoptera in which the prothoracic pleurites are 

 always small and are usually rudimentary. 



The niesothorax of beetles, though more closely united with 

 the metathorax than with the prothorax, yet has in the higher 

 beetles little similarity to the former and its pleura are actually 

 more like those of the prothorax. 



The mesonotum presents many variations in form, but that 

 of Calosoma scrtitator may be taken as a typical example (fig. 

 19). The flat triangular median shield with its apex projecting 

 beyond the rest of the posterior margin is a characteristic 

 feature. Anteriorly a phragma (Ph) projects downward and 

 the posterior edge forms a high ventral ridge. The lateral parts 

 are irregular but the two main processes (a and b) carrying 

 the first and third articular sclerites of the wing (x and s) are 

 present and likewise the posterior axillary arms carrying the 

 axillary cords (Ax). Beneath the outer ends of these lie two 

 little plates (q) that yoke the mesonotum to the metanotum. 

 In some beetles these are fused with the mesonotum and in 

 some cases their posterior ends are fused also with the meta- 

 notum. They are probably equivalent to the yoke plates of the 

 cockroach (figs. 6 and 7, /). The third articular sclerite of the 

 wing (s), which in all normal wings carries the anal veins, is 

 here connected principally with the basal membranous fold of 

 the elytron, and when the latter is folded its anal angle overlaps 

 the sclerite. 



The mesopleurum is sufficiently shown by figs. 16, 17, 21, 

 and 23. Its form does not vary much and there are always 



