INTRODUCTION. 



The antemm ofPer very valuable and important characters both 

 generic and specific; the number of segments may be as few as 

 ten or as great as fifty. The first or basal segment is relatively 

 large generally clubbed at the apex ; in Eudohrnia this segment 

 has two distinct keels. The second segment is invariably minute 

 andcyhndrical; the third is of very variable length and form 

 being cyhndncal ovate, or clubbed; the fourth segment is 

 usua ly_ minute, shorter than the third and generally more 

 simple in shape; it is sometimes barely half as long as the third 

 but occasionally equals it or even slightly exceeds it in length.' 

 Ihe fifth segment resembles the fourth, bnt is always a little 

 longer ; the rest of the segments are each a httle longer than the 

 preceding one ; sometimes the fifth equals the length of the 

 third but when it falls short the sixth is the first to equal 

 the third. _ The relative length of the third, fourth, and fifth 

 segments is one of the characters most valuable to the Derm- 

 apterist. The segments may be absolutely cylindrical, in which 

 case they are usually very slender; more or less ovate or spindle- 

 shaped, subcorneal or clavate, or sometimes decidedly conical 

 in which case the apex of the cone is invariably directed basally' 

 * e backwards towards the head. Sometimes "the segments are 

 globular, and no_ longer than broad, and as a rule th? fewer the 

 segments the thicker they are and the more removed from cyhn- 

 dncal. In Mnnisolahis phihtas. Burr, there are only nine 

 segments, but in Apaclujmfece, Borm., there are nearly fiftv 



ihe thorax consists of three segments, t\xQ pro-, meso- and meta- 

 tJiorax, each covered by a dorsal sclerite, the pro-, meso- and meta- 

 notum respectively. The pronotum is a flat disc of very varied 

 shape ; it is as a rule more or less quadrangular • the' hinder 

 margin IS generally more or less rounded in winged forms, or 

 at least the hinder angles are rounded; in the wingless forms 

 the hinder margin is usually truncate; the anterior margin ia 

 usually truncate, but occasionally narrowed and produced Tnto a 

 kind of neck. The pronotum is sometimes oval, or almost 

 circular. Very useful characters are afforded by the diflferent 

 shapes of this plate : the anterior portion or prozona is generally 

 more or less tumid, while the posterior portion or metazona is as a 

 rue flattened. There is often a more or less distinct median 

 sulcidus or furrow, which may pass into a faint ridge or keel 

 eathrde '° ^^'^ ^"""'""^ ^^^""^ '' frequently an impression on 



.i,'''^u-?r''f'*"' ^^''"®' *^'® ^^•^^^^'-'^ ^^'^^^ these are present, and is 

 thus hidden from view ; in apterous forms it is visible as a short 

 transverse plate ; in the Brachjlahince it is often furnished on each 

 side with an obhque tumid ridge or keel. 



The metanotum carries the functional wings when these are 

 present; in apterous forms it is visible as a transverse segment 

 with the anterior margin straight, but the posterior margin shiuate 

 or roundly emarginate. 



b2 



