NO. I(i87. THFj thorax OF I \SE('TS—H\OD(;RAS;^. 531 



The higher families of beetles, illustrated by Ilydrophihis triangn- 

 laris (134), Melolontlm vulgarw (135, 138), and Cyllene rohinim 

 (140), have a presciitiim somewhat different in appearance from that 

 oi Calosoma and Dytiscus. In Flydrojyhihis (134) anA Cyllene (140) 

 its median j)art {j^sc) is narrow and arched forward, and the mem- 

 branous area {mh) back of it is extended transversely. The scutel- 

 lum {scl) appears to have a long median tongue {G) by itself entirely 

 separating the scutum into lateral halves. The anterior scutal subdi- 

 visions, in front of the transverse dividing lines (w), which are in- 

 complete in Ilydrophihis, are reduced to turgid antero-lateral corner 

 lobes. The lateral extensions of the scutellum in each of these genera 

 fuse laterall}^ with the parts in front of them, so that the axillary 

 cords {AxC) appear to be attached to the margins of the scutum (134, 

 140). Melolontha vulgaris departs still more widely from the 

 Calosonia-Dytiscus type. The median part of the prescutum is 

 I'epresented entirely by the very large prephragma (135, 138, Aph), 

 Avhich is supported by the lateral parts of the prescutum and sepa- 

 rated from the scutum and scutellum by an extensive membranous 

 area (mh). The scutum (135, set, set) is divided, as in the other 

 genera, into lateral halves by a median tongue of the scutellum (scl) 

 on the floor of the median notal groove (G), but the transverse ridges 

 (138 'ir)are coincident with the anterior scutal margins and do not 

 subdivide the scutal plates. The scutellum (scl) is not defined later- 

 ally, but two triangular postero-lateral divisions of the scutum, the 

 " scapulaire posterieure " of Straus-Durckheim (1828) carry the pos- 

 terior notal processes {PNP) and the axillary cords. 



The pseudonotum is well developed in all of these genera (134, 135, 

 140, FN) and carries the postphragma (Pph). The latter is spe- 

 cially large and of complicated structure in Melolontha (139, Pph). 



The mesonotum of beetles is ap]^arently constructed on the same 

 plan as the metanotum. A pseudonotum is lacking. In Calosoma 

 (127) and Dytiseus (128) the prominent shield-shaped area {scl) 

 corresponds Avith the median part of the scutellum of the metanotum, 

 lateral arms extending from it which carry the axillarj^- cords {A,r('). 

 Laterad of the median shield are the separated halves of the scutum 

 {set) carrying the posterior wing processes of the notmii {PNP). 

 In front of it is a large complex prescutal part {psc) carrying the 

 anterior phragma {Aph) and laterally the anterior notal wing 

 processes {ANP). Two little plates {q) lie between the mesonotum 

 and the metanotimi. These may be rudiments of a mesopseudonotum, 

 but they are more closely connected with the metanotum than with 

 the mesonotum. On the ventral surface of the mesonotum (131) a 

 V-shaped ridge (F) is present similar to that of the metanotum. In 

 most other beetles the parts of the mesonotum are so blended that any 

 plan of structure closely corresponding with that of the metanotum 



