STOMOXYS CALCITRANS LINN, PART II.* 



By Chas. K. Brain. 



The Circulatory System. 



The circulatory system in Stomoxys calcitrans consists, as in 

 other Diptera, of the dorsal vessel or heart, and its anterior 

 continuation, the thoracic aorta. The dorsal vessel extends 

 as a delicate tube from the posterior part of the abdomen to 

 its anterior sixth, that is above the anterior part of the sucking 

 stomach, where it becomes narrowed into the thoracic aorta. 

 This narrowed portion continues of uniform thickness until 

 the proventriculus is reached, where it becomes somewhat 

 flattened and wider. Beyond this it becomes narrower, and 

 terminates above the esophagus, between the proventriculus 

 and the neck. 



It may be noticed that, as found by Professor Minchin in 

 his study of Glossina sp., the dorsal vessel ends blindly behind, 

 is composed of similar giant cells, and has similar ostia and 

 alary muscles. The number of chambers in the heart was not 

 determined with certainty, but I think Tulloch was correct 

 in supposing that there were four. The dorsal vessel lies free 

 in the pericardial cavity, but is supported by the muscular 

 pericardial septum. 



Nervous System. 



There are two chief ganglia, viz : the brain and the thoracic 

 ganglion, and from these the main nerve-trunks arise. Time 

 was not taken to work out the more minute nerves, but the 

 following may be mentioned. The chief nerves of the head 

 beyond those of the compound eyes, are those which enervate 

 (a) the antennae, (b) the ocelli, and (c) the esophagus, pharynx, 

 and the pharyngeal muscles. 



The brain is connected with the thoracic ganglion by com- 

 missures, between which the esophagus passes. The thoracic 

 ganglion is roughly pear-shaped, and is supported by the 

 internal chitinous skeleton of the thorax. The main nerves 

 given off from the thoracic ganglion are (a) six pairs which 



*The first part of this paper, which dealt with the external mouthparts and 

 the digestive system, appeared in Vol. V, No. 4, pp. 421-430 of these Annals, 

 December, 1912. 



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