586 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



which is anterior to the pleural notch, but is here a small, triangular 

 structure, and does by far not reach the ventral middle line of the 

 segments. A distinct Preeusternum is not developed except in 

 Necrohia and, less pronounced, in some species of Enoclerus. Euster- , 

 num {es) is large, subtriangular, without any longitudinal muscle 

 impression in front of parasternum. Parasternum {pas) is well de- 

 fined, subtriangular, with straight interior limitation. The Medio- 

 sternellum {mstl), posteriorly ending at the sternal notch, has nor- 

 mally the shape of a small, narrow, transversal band with lanceolate 

 or subtriangular outline ; it is unusually large and swollen in Tarso- 

 stenus. The Laterosternellum {Istl) is in most genera small, even in- 

 distinct; when well developed, as in Enoclerus and Cymatodera^ it 

 reaches the sternal notch and has a shape similar to parasternum and 

 limiting lines parallel to those of that area. The Poststernellum 

 {post) lies behind the mediosternellum and laterosternellum of the 

 segment and in front of the presternum and eusternum of the next 

 segment; it is developed as intersegmental membrane; usually of 

 moderate size, but large in the elongate, vermiform genera. The 

 Coxal Lobe is between hypopleurum, parasternum, and lateroster- 

 nellum ; it is small, often indistinct and confluent with parasternum. 



The ninth abdominal segment consists of a large dorsal region, 

 containing both tergal and epipleural elements, and a narrow band- 

 like ventral region with hypopleural and sternal elements; the two 

 regions are separated by the ventro-lateral suture ; none of them are 

 differentiated into special areas. In the different species of the large 

 genus Enoclerus and also in many other genera, a pair of solid, 

 usually not branched, well-developed Cerci {cer^ fig. 79) extend from 

 an unpaired, chitinous basal plate {hp) on the dorsal i-egion; the 

 shape and size of both cerci and basal plate vary considerably in the 

 family. In Necrohia the cerci are slightly branched ; in some species 

 of Cymatodera., as CymModera bicolor, they unite into a single, 

 bifurcate, stalk-like formation, which arises from a well-developed 

 disciform basal plate; in Priocera castanea the cerci are small and 

 fused into a bifid, conical horizontal prolongation of the basal 

 chitinization, which in this form envelops the whole dorsal region; 

 in Thaneroclerus girodi the cerci are rudimentary, but the basal 

 plate is well developed ; in Hydnocera. the cerci are rudimentary and 

 the basal plate is not sharply defined ; Phyllohaenus and Orthopleura 

 have a pair of hook-shaped cerci, but no basal plate, and Neichnea 

 has neither cerci nor basal plate. 



The tenth abdominal segment is developed as a locomotive organ 

 and placed entirely below the ninth segment; it is wart-shaped, ring- 

 like with a triangular anus, which is surrounded by four small 

 papillae in front and one large, lip-like lobe behind. 



