MUSCULATURE OF DIPTERA — SMART 335 



The basalar sclerite is large, heavily sclerotized, and deeply invagi- 

 nated. The subalar sclerite is weakly sclerotized and not easily 

 distinguished. 



The mesothoracic coxa is large, has a well-developed meron and a 

 very limited capacity for articulation on the thorax. The meron is 

 still part of the coxa and has not become detached, as in higher Dip- 

 tera, and fused to the thoracic wall to form what the systematic dip- 

 terists term the hypopleuron. 



The mesothoracic sternum gives rise, at the innermost anterior part 

 of the cleft between the mesocoxae, to a well-developed and heavily 

 pigmented furca. 



Anisopus is not a strong flier, and the various sclerites that com- 

 pose the articulation of wing to thorax are weakly sclerotized and not 

 at all easy to distinguish, a disadvantage when tracing the insertions 

 of the direct wing muscles. 



The metathorax bears well-developed halteres ; the legs have large 

 coxae and have a free though limited articulation. The lateral ele- 

 ments of the metapleural wall can be distinguished ; the dorsum is 

 reduced to a ribbon that passes over the mesothoracic postnotum and 

 is itself in turn covered by the anterodorsal margin of the first ab- 

 dominal segment. 



4. THE MUSCLES OF THE MESOTHORAX OF ANISOPUS 



Originally I intended to describe the entire musculature of Ani- 

 sopus. I soon realized, at a date prior to the publication of Tieg's 

 (1955) paper, that the musculature of the mesothorax was not primi- 

 tive. In particular I could find no trace of the mesothoracic tergal 

 depressor of the trochanter muscle of Tabanus (Bonhag, 1949), 

 Calliphora (Ritter, 191 1), Drosophila (Miller in Demerec, 1950), 

 Psychoda (Feuerborn, 1927; Dirkes, 1928), Orthellia, Calobata, 

 Lathyrophtalmus, and Pecticus (er. pro Ptecticus) (Maki, 1938). A 

 tergal depressor of the trochanter is found in generalized insects such 

 as the locust (Albrecht, 1953), the cockroach (Carbonnell, 1947), 

 and is regarded as one of the basic muscles of the unspecialized ptero- 

 thoracic segment. It is also present in Panorpa (Hasken, 1939), 

 Boreus (Fuller, 1955), and Bittacus, and would therefore be expected 

 in any dipteron with any claims to real primitiveness. 



A second purely practical reason for curtailing the work on Ani- 

 sopus was that the weak sclerotization of the exoskeleton coupled with 

 the small size of the creature made it difficult to identify the final 

 insertions of pleural muscle tendons. 



