C6 CHIRONOMUS PRASINUS. 



In this Journal I have on previous occasions illustrated the 

 structure and economy of three species of Dipterous larvse,* which 

 may form useful points of reference and comparison in dealing 

 with our present subject. Of these, that which it most resembles, 

 both in external form and in internal structure, is the larva of 

 Ta?iypus macidatus^ the most conspicuous difference being that of 

 colour, for whilst the larva of Ta7iypus is colourless, that of Chiro- 

 7iofnus is bright red, a distinction which, I have Mr. Sorby's 

 authority for saying, is due to the presence of hoemoglobin in the 

 blood. As in the annelids, however, Tiibifex, e.g., the colouration 

 resides not in the corpuscles of the blood but in the plasma itself. 

 Like Ta7iypus, the body is furnished wdth two pairs of grappling 

 feet, having coronets of booklets. These are evidently homologous 

 with the prolegs of the Lepidoptera. I have found a dipterous 

 larva in which all the abdominal segments were provided with 

 similar organs, but, like a great many others with which I am 

 acquainted, I am quite unable to identify it. It should, however, 

 be noticed that while the first pair of Hmbs in our present subject 

 is found on the prothoracic segment, this never occurs in cater- 

 pillars, and also that as contrasted with Ta?iypcs, where they are 

 partially fused, they are here quite separate. The crop, which in 

 Ta?iypiis assumes the form of a simple enlargement of the alimen- 

 tary canal preceding the proventriculus,t and in the Blow-Fly that 

 of a pendent pouch or sac, is in the present case entirely wanting, 

 and the oesophagus opens directly into the proventriculus, a 

 difference which may result from the nature of the food, which in 

 the two former cases consists of animal matter, but here is com- 

 posed of fine mud and such nutritious materials as it may contain. 



Another point, too, is remarkable, As contrasted with the 

 Blow-Fly, Psychoptera, and most other insects, this larva is, in the 

 earlier stages at all events, distinguished by the almost total 



* On the Larva of Tanypus macidatus. See this Journal, Vol. I., p. 83, 

 On the Maggot of the Blow Fly., Vol. II., p. 33. On Psychoptera paludosa, 

 Vol. III., p. 69. 



+ Mons. Felix Plateau, in a paper on the digestion of insects in the 

 Memoires de 1' Academic Royale de Belgique, Tom. xli., 1S75, advocates with 

 considerable force of reasoning the abandonment of all the nomenclature 

 usually applied to the alimentary canal of insects, which presupposes the exist- 

 ence of an organ analogous to the stomach of vertebrates. I think it best, 

 however, to use the ordinary nomenclature, at all events for the present. 



