MUSCULATURE OF DIPTERA — SMART 353 



and no branch muscle originating on the basalar sclerite. These two 

 muscles insert on the mesial tendon of the trochanter along with two 

 other muscles with coxal origins. 



The condition of the muscles in Megaloptera has been reported 

 on by Maki (1936) in Chaiiliodes, by Czihak (1953) in Sialis, and 

 by Kelsey (1957) in Corydalus. Wittig (1955) has described the 

 condition in Plecoptera in Perla. 



Maki (1938) states that in Neopanorpa (Mecoptera) there is in- 

 serted on the mesial depressor apodeme of the trochanter in the ptero- 

 thoracic segments : ( i ) a very thick muscle originating on the ter- 

 gum, (2) a slender f aside originating on the basalar plate, and (3) a 

 sternal depressor originating on the arm of the f urea. Hasken (1939) , 

 apparently unaware of Maki's paper, described the same muscles as 

 Maki except that he does not seem to have appreciated that the basalar 

 fasicle inserted on the same apodeme as the tergal and sternal (f ureal) 

 muscles ; he noted three coxal muscles similarly inserted and two 

 others acting as additional depressors as in the cockroach. 



Serial sections of the muscles of the thorax of Panorpa show that 

 all thoracic muscles, including the indirect flight muscles, TDT muscle, 

 coxosubalar muscle, and other pleural and leg muscles, are of similar 

 histological structure ; they are not separable into two types, fibrillar 

 and tubular, as in Diptera. 



Maki ( 1938) noted the absence of a TDT muscle in the mesothorax 

 of a tipulid and its presence in four other Diptera. He did not record 

 that the literature at the time he wrote indicated that there was a 

 TDT muscle in Psychodidae (Feuerborn, 1927; Dirkes, 1928), as 

 well as in Calliphora (Ritter, 191 1) and in syrphids (Kunckel d'Her- 

 culais, 1875-1881). 



Tiegs (1955) noted the condition of presence or absence of this 

 mesothoracic TDT muscle in examples of 11 families of Diptera. 

 Smart (1958) gave an account of a more extended survey of Diptera 

 in respect to this muscle ; table 4 is derived from Smart (loc. cit.) 

 with additions. 



My examination of an extensive series of Diptera shows that: (i) 

 In Diptera the furcal depressor muscle is, as far as I can ascertain, 

 always present. It is also present in Panorpa (Maki, 1938; Hasken, 

 1939). (2) The basalar depressor muscle is never present in Diptera. 

 It is present in Panorpa (Maki, 1938; Hasken, 1939). (3) In Dip- 

 tera the tergal depressor is either present or completely absent and is 

 a single muscle when present. It is present in Panorpa (Maki, 1938; 

 Hasken, 1939). (4) In Anisopus and in such other Diptera as have 



