1920] Du Porte: Muscular System of Gryllus 19 



one small basalar sclerites (b.s.) and two subalar plates (s.a.p.), 

 the anterior one elongated, the posterior smaller and broadly- 

 oval. 



The Abdomen (Figs. 1 and 3). Several small chitinous 

 plates are imbedded in the pleural membrane of the abdomen. 

 The parasternal plate (Fig. 1, ps.p.) situated immediately 

 behind the base of the third coxa, is the largest of these 

 sclerites. Judging by its musculature this plate is apparently 

 a detached portion of the first and second abdominal sternites. 

 In each segment from the third to the seventh there are three 

 small linear pleural sclerites, one (p.Si) near the anterior end, 

 one (P.S2) near the posterior end and the third (p. S3) in the 

 middle of the segment nearer the tergum than the two other 

 pleural sclerites. In the third segment the third pleural 

 sclerite is large and receives muscles from the second and third 

 sternites. 



From the anterior edges of the eighth and ninth tergites in 

 the female, a flattened blade-like process (Fig. 3, PAs, PA9) 

 projects forward. These processes serve as points of origin for 

 certain of the muscles which move the ovipositor. The supra- 

 genital plate bears a median knife-like process (Fig. 3, P.S.G.) 

 which serves the same purpose. 



A ventral (Fig. 3, Vi, V2) and a dorsal process (di, d2) are 

 given off from, the base of each gonapophysis ; these serve as 

 points of insertion for muscles of the ovipositor. On each side 

 the two dorsal processes (di and d2) are closely interlocked. 

 The ventral processes (vi) of the dorsal pair of gonapophyses 

 (G. D.) are connected by means of a transverse chitinous rod 

 (Fig. 3, t.c.) which bears a flat, thin unpaired process (m) 

 in the middle of its anterior face. 



II. THE MUSCLES OF THE HEAD. 



The muscles of the head may be divided into (a) the muscles 

 of the mouthparts, (b) the muscles of the antennae, (c) the 

 muscles of the pharynx and oesophagus, and (d) the cervical 

 muscles, or those which control the movements of the head 

 as a whole. 



{a) . The Muscles of the Mouthparts. 

 The Labrum. — The Abductors of the Labrum (Figs. 7 and 9, 

 abd.lbr.) are a pair of contiguous muscles, straight with parallel 



