NO. 13 STAPHYLINIDAE BLACKWELDER 3I 



tension, the pleuradema (pld). The dorsal edge of the sternepimeron 

 bears the sternepimeral suture (fig. 3 A, seps), which marks the 

 invagination of the sternepimeral ridge (fig. 5 A, scpr). Apparently 

 arising from the cephalic end of the episternum is the very large 

 pleural disk (mdpt) which extends posteriorly, overlapping the base 

 of the wing. 



The endosternites of the prothorax consist of a broad prephragma 

 (fig. 5 B, prph) and the sternal apophysis (sa). The prephragma 

 arises from the anterior edge of the basisternum (fig. 3 A, bs) and 

 forms the ventral border of the anterior foramen (afor). It extends 

 the width of the basisternum and unites with the sternal apophysis 

 entad of the sternonotal suture (sns). From each lateral corner of 

 the furcasternum (fs) arises a sternal apophysis which extends along 

 the lateral edge of the sclerite to unite with the prephragma and the 

 pleural apophysis. Near the base of each sternal apophysis is the 

 large muscle disk (mdsp). 



In the mesothorax the sternum bears a transverse ridge on its 

 posterior margin. This ridge is the furca (fig. 5 B, fii) and has two 

 anterior projections, the furcal arms (fua). The two muscle disks 

 (mdss) apparently arise from the furcae also. The spinisternum 

 (fig. 3 A, ss) also bears a small transverse ridge (fig. 5 B, ssr) with 

 a median cariniform projection, the spina (spn). 



The metathoracic endosternites (fig. 5 B) are more properly termed 

 the furca than those of the mesothorax. The prominent part is the 

 median bar (fu) arising from the posterior border of the sternum 

 and projecting anteriorly in the interior of the thorax. In approxi- 

 mately the middle of the metathorax it divides into two lateral 

 branches, the furcal arms (fua), each of which bears a large muscle 

 disk (ntdst). A narrow ridge is formed on the ental surface of the 

 caudal and lateral margins of the sternum, extending anteriorly to the 

 region of the pleural coxal process of the mesothorax. 



THE APPENDAGES OF THE THORAX 

 THE WINGS 



The elytra are highly modified wings of the mesothorax. They have 

 a horny texture and considerable rigidity but are not used in flight. 

 They are held apart at an angle with the body to allow freedom of 

 motion of the wings, but when at rest are laid along the dorsum of 

 the mesothorax and metathorax, meeting along the midline. They 

 serve as covers for the wings, but are so small in this species that 

 the wings must be folded transversely under them several times. 



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