(98) 



538 0. GORDON HEWITT. 



by means of an anterior and a posterior pair of spiracles. 

 The anterior spiracles, which do not occur in the first larval 

 instar, are considered to be functional. 



12. The vascular system consists of : (1) A dorsal vessel, 

 the posterior region of which is swollen to form a cardiac 

 region or "heart" which communicates with a pericardial 

 cavity by means of three pairs of lateral ostia ; (2) the great 

 ventral sinus, which forms the body cavity ; and (3) the peri- 

 cardial sinus. The pericardium is well supplied with tracheae, 

 which may assist in respiration, as in certain other insect 

 larvae. The adipose tissue cells which compose the large 

 laminae forming the fat-body are similar in structure to those 

 of the fly. 



13. Three groups of imaginal rudiments or discs can be 

 recognised in the larva : (1) The cephalic discs, of which two 

 appendicular pairs are situated at the anterior end of the larva 

 and three pairs in front of the cerebral lobes of the ganglion ; 

 (2) the thoracic discs, two pairs of which are attached to the 

 anterior end of the ventral side of the ganglion, and three 

 pairs are connected with the lateral tracheal trunks in the fifth 

 segment ; (3) the abdominal and visceral discs. 



VII. LTTEKATUEE. 



For the sake of convenience a few of the references given 

 in Part I have been repeated here. 



1902. BERLESE, A. "L'accoppiamento della Mosca domestica," 'Rev. 

 Patalog. vegetale,' vol. ix, pp. 345357, 12 figs. 



1834. BOUCHE, P.FR. ' Naturgeschichte der Insekten besonders in hinsicht 

 ihrer ersten Zustande als Larven und Puppen,' Berlin, 216 pp., 

 10 pis. (M. domestica, pp. 65, 66, pi. v, figs. 2024.) 



1883. BRAUER, F. "Die Zweifluger des kaiserlichen Museums zu Wien : 

 III. Systematische Studien auf Grundlage der Dipteren larven nebst 

 einer Zusammenstellung von Beispielen aus Literatur iiber dieselben 

 und Beschreibung neur Formen," ' Denkschr. der Kais. Akad. der 

 Wiss. math-naturwiss. Classe/ Wien, vol. xlvii, pp. 1 100, 5 pis. 



