582 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



pterygium and deltoid Lowne (1902), Analwurzel'platte and hintere 

 Analgelenhplatte Voss (1905). Mesoptero Berlese (1906). 



Thorax. — The middle division of an insect, composed of three seg- 

 ments — the lyrothorax., the mesothorax., and the metathorax. The 

 microthorax is the segment of the neck sclerites and the labium, and 

 there is, hence, no reason for counting it as a thoracic segment. The 

 primitive thoracic region may have been composed of a greater num- 

 ber of segments than three, but the extra ones have disappeared or 

 remained only as small intersegmental plates in some of the Aptera. 

 Trvnem Fabricius (1778), Kirby and Spence (1826). Thorax Cha- 

 brier (1820), Audouin (1824), Corselet (prothorax) and thorax 

 (meso- and metathorax) Straus-Diirckheim (1828). 



Tibia (Th). — The fourth joint of the leg, between the femur 

 and the tarsus. Tibia Fabricius (1778). Cubitus of front leg, tibia 

 of middle and hind legs, Kirby and Spence (1826). Jambe Straus- 

 Diirckheim (1828). 



Trochanter (Tr). — The second joint of the leg, between the coxa 

 and the femur. It consists of two subjoints in some Ilymenoptera. 

 Scapula of front leg, trochanter of middle and hind legs, Kirby and 

 Spence (1826). Trochanter Straus-Diirckheim (1828). 



Trochantin (Tn). — The plate of the thoracic wall anterior to the 

 base of the leg, articulating above with the episternum and below 

 with the ventral rim of the coxa. It is large and prominent iii most 

 of the lower insects, but is frequently absent or fused with the 

 sternum or episternum in the higher orders. It is situated on the 

 side of the thorax, but may be a sternal plate in its origin. The 

 coxa is normally articulated above to the coxal process {CxP) of the 

 pleurum, and below to the coxal process of the trochantin (TnC). 

 Only in rare cases is it articulated to the sternum, as in the nymphs 

 of Odonata. Trochantin Audouin (1824), VerhoefF (1903), "^Snod- 

 grass (1908), Crampton (1909). Rotule Straus-Diirckheim (1828). 

 Trochantimis Kolbe (1889). Not the trochantine of Packard 

 (1898). First antecoxal piece (Blattid?e) Comstock and Kochi 

 (1902). Pracoxalplatte {Trochantin) Voss (1905). Trochantino 

 Berlese (1906). 



Vena diridens (D). — The secondary vein developed in the first 

 anal fold of the wing of some insects, especially in Orthoptera. 



Ve7iter. — The entire morphological ventral surface of the insect or 

 of any part or segment, corresponding with the dorsum above. The 

 sterna are the segmental chitinizations of the venter, and the stemites 

 (as used in this paper) the sclerites of any sternum. 



^yings (W., WJ. — The organs of flight. In the nymphs of insects 

 with incomplete metamorphosis the wrings appear to be extensions of 

 the lateral edges of the meso- and metathoracic terga. In adults they 



