S07ne Dipterous Larvce. 603 



(1915, pp. 173-177*), and which are present in all Cyclo- 

 rhaphous larvse ; and {d) labial palps in the foira of small 

 conical protrusions, each of which bears a single circular 

 papilla. The ventral surface of the head-lobes is raised in 

 several rows of rib-like projections, armed with strongly 

 chitinised, bifid, reflexed hooks. Each of the three thoracic 

 seyiuents bears on its anterior part several sinuous rows of 

 small booklets and a definite number of sensory hairs and 

 pits. The vestigial remains of the thoracic legs are repre- 

 sented by six groups, each consisting of three small sensory 

 liairs. The prothoracic segment bears the pair of well- 

 devffloped anterior spiracles. The first seven ahduminal 

 segments are twice as long as broad ; they present a doubled 

 aj)pearance, owing to the conspicuous zone of articulation, 

 where the segments are tele:scoped into each other. Each 

 segment bears at its anterior border several sinuous rows 

 of small reflexed booklets. On the ventral surface of the 

 eighth and last abdominal segment is the anus, which divides 

 the segment into an anterior portion resembling that of the 

 })rec(ding abdominal ^^egments and a posterior portion 

 which is prolonged into the res])iratory siphon. Tiie 

 ])roximal portion of the siphon resembles the corresponding 

 portion of an ordinary abdominal segment ; it becomes 

 narrower posteriorly, forming an ihtermediate portion which 

 is covered -with small, forwardly-directed booklets. The 

 terminal portion of the siphon is slender, rigid, and tubular, 

 and bears the pair of postabdominal spiracles at its 

 extremity. 



The respiratory system of this larva is amphipneustic ; 

 two pairs only of functional spiracles are present — the pro- 

 thoracic and the postabdominal pairs. The prothoracic 

 spiracles (fig. 3, s) comprise eight elongated papillae which, 

 by means of a well-developed felt-chamber, communicate 

 with the two lateral tracheal trunks. The postabdominal 

 spiracles (fig. 4) are situated at the extremity of the respi- 

 ratory siphon, and, on account of the tip of the latter being 

 bifurcated, are separated from one another by a fairly deep 

 groove. Each spiracle appears to possess three spiracular 

 clefts, surrounded by long divergent hairs. The felt- 

 chamber, through which the spiracles communicate with the 

 tracheal trunks, is very long and narrow. 



The bucco-pharyngeal organ (fig. 3) shows the structure 

 typical of ail the Cyclorhaphous Diptera ; it is comprised of 



* Keiliu, 1). (1915). " Rechercbes sur les larves de Dipteres Cyclo- 

 rliaphes," Bull. Scieut. de la France et Belgique, 7* serie, vol. xlix. 

 pp. 15-192. 



39* 



