524 



PROCEEDINGS OF THE NATIONAL :\IVSEVM. vol. xxxvi. 



cliitinization of the infolded intersegmental membrane behind the 

 pseudonotum, for it is always composed of two closel}^ appressed or 

 fused lamina\ The first is directly continuous with the pseudo- 

 notum, the second is connected with the notum of the segment fol- 

 lowing, generally by membrane but sometimes directly, as when the 

 segments are fused. 



The pseudonotum is conspicuous in the metathorax of Coleoptera 

 (132-140, PX). It is the plate that Straus-Diirckheim (1828) 

 named the " tergTmi " in Mdolontha vulgaris (135, PN), but most 

 authors have followed Audouin (1824) and Newport (1839) in call- 

 ing it the '"postscutellum/' This name is appropriate when a scutum 



and scutellum can be distinguished. 

 Berlese (190G) recognizes and fig- 

 ures the plate in the Coleoptera, 

 but he refers it to the abdomen, 

 calling it the " acrotergite " of the 

 first abdominal segment. Such a 

 disposition of the sclerite, liow- 

 ever, is clearly impossible on ac- 

 count of its intimate connection, 

 an articulation (/) in beetles, with 

 the epimera of the metathorax. In 

 the mesothorax of Cole()i)tera there 

 is no pseudonotum unless the two 

 small plates (127, 128, 131, 7) 

 yoking the mesonotum to meta- 

 notum are rudiments of it. The 

 pupjie of beetles do not show a 

 pseudonotum even in the meta- 

 thorax. In Dendroctonufi valeiifi 

 (122, 12G), and in Tetrophnn 

 I'ehithncm (123) it is easy to see 

 that no pupal plate intervenes be- 

 tween the metathoracic notum or wing-bearing sclerite (.V,,) and 

 the first abdominal tergum {IT). The latter can be identified by 

 the first abdominal spiracles. 



In the Plecoptera the pseudonotum is a large, simple plate in both 

 the meso- (75) and the metatergum. It is partly overlapped by the 

 notum {N). In a nymphal tergum, hoAvever, there is no trace of it 

 (76), and its site is entirely inembranous (Mh). It is similar in 

 Neuropteran adults (142), but lacking in the pupa (141). 



In the Lepicloptera (149), the Hymenoptera (169), and the Diptera 

 (174 and 179) the pseudonotum is present in both segments and is 

 easily distinguishable as the tergal plate behind the wing bases. In 

 the mesothorax of these orders it carries tlie large phragma (150, 



Mb 



Fig. 2. — L)ia<;i;am.\i.\ti(' tkkoi'.m of any 



t'U.Ml'MOT.: \Vi.\(i-Ui:AIiIN.! .SIOCMKNT, 



VE.NTUAL \IK\V ; AyP, ANTEIilOl! NOTAI, 



WINIi I'UOCKSS ; AXR, AXTEKIOU NOTAI. 



• RIDGK ; Aph, I'I{KPHUA(J.MA ; AdC, AXIL 



LAKY cord; Em, lateral emaugina- 



TION OV TUB XOTIM ; Mh, MEMltUAXi: 

 BETWEEN NOTU.M AND I'SEUDONOTUM ; 



y, NOTUM ; P\, rsEfDoxoTi.M ; pyp. 



POSTEIIIOU NOTAL WIXG I'ROCE.SS ; PXP, 

 PO.STEUIOR NOTAL lilDGE ; Pph, POST- 



i'iiisagma; 7?^/, posteriou reduplica- 

 tion or the NOTi'M : T", V-shaped 



ventral ridge of NOTU.M, THE ENTO- 

 DORSUM. 



