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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



to six. These bands or ridges resemble the parapsides of the meta- 

 thorax both in structure and in position. Punctures are numerous in 

 all the plates and the lateral limitations are always irregular. The 

 seventh and eighth tergites in the males and the seventh in the females 

 are heavily chitinized and lack the above mentioned armature but 

 have numerous hairs and punctures. 



Lateral plates or pleuritcs. — The pleural suture seems to be the 

 line which divides the heavily chitinized hypopleurites from the mem- 

 branous epipleurites. The pleural suture is not visible in the seventh 

 and eighth pleurites because the epipleurite is heavily chitinized here 

 and completely fused with the tergite. The second hypopleurite which 



Fig. 21. — Gnathotrichus materiarius Fitch: Abdominal sternites, ventral aspect. 

 St, sternites; a, coxal cavity; b, clavicula; c, intercoxal process. 



extends beyond the postepimerum of the metathorax is ventrally de- 

 fined by a suture while the others are fused ventrally with the sternites. 

 The former corresponds to the second tergite. The hypopleurite be- 

 longing to the first tergite is not represented as a plate but fused with 

 the epipleurite. The hypopleuritic areas are covered by the elytra when 

 they are kept in the closed position, and form a vertical plane, while the 

 sternites make an angle of about 120 degrees with them. As was men- 

 tioned before, the epipleurites are membranous except those which cor- 

 respond to the last tergites. The hypopleurites corresponding to the 

 last seventh and eighth tergites are present only as narrow membranes. 

 Ventral plates or sternites. — In both sexes only five ventral plates 

 or sternites are distinctly defined by sutures as is illustrated in figure 

 21 and they represent the sternites three to seven. The sternites are 



