580 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



(1903), (as a general term) Snodgrass (1008). Acrotergite of fol- 

 lowing tergum, in most cases, Berlese (1906). 



Radius {R). — The third principal vein of the wing, associated at 

 its base with the second axillary. 



Sclerite. — Any one of the chitinoiis plates of the body wall or of 

 the appendages. 



ScuteUum {Scl). — The third division of the notnm, often forming 

 a prominent shield-shaped or triangular elevation. Xot homologous 

 in all orders. /ScuteUum (the raised part of dorsum between wings) 

 Fabricius (1778). Postdorsum or podorsiDu Chabrier (1820), Am- 

 ans (1885). ScuteUum Audouin (1824), Newport (1839), Kolbe 

 (1889), Crampton (1909). ScuteUum (median) and frmnuin (lat- 

 eral) in mesothorax, postscuteUmn in metathorax, Kirby and Spence 

 (182G). Pustscutum Voss (1905). Metaterylte Berlese (190G). 



Scutu/m (Set). — The second division of the notum. Not homolo- 

 gous in all orders. Ecusaon and dorsum Chabrier (1820). Scutum 

 Audouin (1824) Mac Leay (1830), Newport (1839), Kolbe (1889), 

 Voss (1905), Crampton (1909). Dorsolum, in mesothorax, postdor- 

 solum in metathorax, Kirby and Spence (1826). Dorsum Amans 

 (1885). Mesotcn/ite Berlese (190()). 



Second axiUAiry {2, 2 Ax, ohlique sJiading in mihroken lines). — 

 The pivotal sclerite of the wing base, resting upon the pleural wing 

 process, articulating with the first axillary mesially and usually with 

 the base of the radius distally. Petit liu/meral in front wing, dia- 

 demed in hind wing, Jurine (1820). OmopJate Chabrier (1820). 

 Epauliere anterieure of elytron, seconde axillaire of hind wing, 

 Straus-Diirckheim (1828). Suhmedlan Xm'3iiiS (1885), Petri (1899). 

 TJnguiculus Lowne (1892). MitUegelenl'platte Voss (1905). Pos- 

 terior sclerite of proptero Berlese (1906). 



Segment. — An}^ one of the divisions of the head and body corre- 

 sponding with the primitive nietameres. The head is a combination 

 of segments. Also any one of the joints of the legs or antennae. 



Segm^ent mediaire {IT in Hymenoptera ) . — See Median segment. 



Spiracle (Sp). — Any one of the breathing apertures of the trach- 

 eal system, situated, in adult insects, along the sides of the body. 

 In the thorax there are two on each side, one in the membrane be- 

 tween the pro- and the mesothorax and the other between the meso- 

 and the metathorax. The first is commonl}' regarded as jDrothoracic 

 and the second as metathoracic. But Borner (1903) regards the first 

 as mesothoracic and the second as metathoracic, because, as he says, 

 it is a well-known fact that the spiracles are developed in front of 

 the sclerites of the segments to which they belong. In Japyx solifu- 

 gus there are apparentl}^ four pairs of thoracic spiracles, but Biirner 

 regards the second two as being abdominal spiracles moved forward. 

 Stigma Audouin (1824), Newport (1839). Spiracle Kirby and 

 Spence (1826). 



