532 PROCEEDINGS OF THE NATIONAL MU8EUM. vol. xxxvi. 



can not be made out. Yet a j^rogressive modification from the CaJ- 

 osoma-Dytiscus type can be traced through Hydroijhilus (125), 

 Cyllene {12d), and Dendroctonus (124). 



It is thus clear that the same fundamental structure of the notuni 

 obtains throughout the Coleoptera, the Lepidoptera, the Hymenop- 

 tera, and the Diptera, but that the notal subdivisions are not neces- 

 sarily determined b}^ it. 



In the Neuroptera a tergum of diagranunatic simplicity is found. 

 In Corydalis (142, 14:3) the scutum {act) and scutellum {scl) are 

 separated along the line (142 r) of the ventral V ridge (143 T^). 

 Anteriorly and posteriorly are narrow marginal areas defined by the 

 anterior and posterior notal ridges (.LAV?. PXIi). The first of 

 these miglit be called the prescutum, but the second is simply tlie pos- 

 terior notal reduplication {Ud) and does not correspond with the 

 postscutellum of higher orders, for this is the i^seudonotum, which 

 is well developed in Con/dalh (142, PN). 



In the Euplexoptera the metanotum of ISpoiu/iplwra (96) consists 

 of an undivided plate carrying both the anterior and the posterior 

 wing process {ANP, PXP), while articulated near the middle of its 

 posterior margin are two long arms (/) bearing the axillary cords 

 (AxC). In the mesonotum (90) there is a large anterior triangular 

 part carying the anterior notal wing processes (AXP) and two lateral 

 divisions carrying the posterior wing processes {PXP) . It is evident, 

 however, that neither tergum of Spongiphora is normal, for neither 

 presents any trace of the V-shaped ridge, and the general shape is 

 peculiar to the order. A ventral view of the mesonotum (92) shows 

 that the two apparent divisions are due merely to elevations and de- 

 pressions of the surface. 



In the Belostomida? of the Ilemiptera the mesonotum presents a 

 wide, strongly declivous prescutal area carrying the prephragma and 

 limited posteriorly by a definite transverse line. Back of it are two 

 transverse grooves separating tliree other divisions. The last is sim- 

 ply the long posterior rechiplication whigh in the Ilemiptera overlaps 

 the mesonotum. There is but a faint trace of the V ridge in Benacus 

 and it does not influence the notal subdivision. The metanotum is 

 also much modified, carrying an unusually large prephragma and 

 lacking the V ridge, tn Bcnacvs (87) it is clear that both of the 

 notal wing processes {ANP and PNP) arise from the scutum. A 

 very narrow pseuclonotum (88 PN) is present, connecting with the 

 epimera lateralh'. The first abdominal tergum {IT) is also much 

 modified and closely connected Avith the pseudonotum. It can be 

 identified by its lateral spiracles (/ Sp.). 



In the Plecoj)tera, as illustrated by Pteronarcys calif ornica (75), 

 the indistinct regions of the notum are due entirely to the topography. 

 The anterior and posterior notal regions are Aveakly developed while 



