606 Dr. D. Keilln on 



abdominal segment is prolonged beyond the anus so as to 

 form a respiratory siphon similar to^ but much shorter than, 

 that of larvte A. The larva is amphipneustic ; the pro- 

 thoracic spiracles (fig. 5) protrude slightly externally and 

 show traces of the spiracular papillse, whose number I could 

 not determine. As in Larvae A, the respiratory siphon is 

 bifurcated at its extremity, and, in consequence, the post- 

 abdominal spiracles are separated by tlie groove of the 

 bifurcation (fig. 7). The Imcco-pharyngeal armature of this 

 specimen resembles that of Larvae A, but the sclerites are 

 relatively more slender (fig. 8). 



The Systematic Position of Larvm A and B. 



As already mentioned, these larvae had been associated by 

 ]Mr. F. W. Edwards with the Eristalinse (Syrphidse). He 

 supplied, moreover, the following information (see Baylis, 

 ]). 379) : — '' Dipterous larvae from Cardiosoma hirtipes. — 

 These larvae are evidently Syrphidae, and apparently belong 

 to the subfamily Eristalinae ; they differ from Eristalis in 

 the more elongate form and the lack of any obvious 

 separation into 'body^ and 'tail.^ 



" Larvae from Gecarcoidea lalandii. — These are also Syr- 

 phidae, but in the present state of our knowledge it is 

 impossible to assign them definitely to any subfamily. 

 They appear to lack the extensile ' tail ' of Eristalis.^' 



The foregoing remarks show that Edwards was guided in 

 liis identifications solely by the general conformation of the 

 body, and especially by the presence of a well-developed 

 posiabdominal respiratory siphon. As a matter of fact, the 

 resemblance between larvae A and an Eristaline larva is 

 most remarkable. It must be remembered, however, that 

 the possession of a postabdominal siphon is merely evidence 

 of the fact that the larva inhabits a fluid or semi-fluid 

 medium, and the greatest caution must be exercised before 

 makiuf^ use of it as a character for the purpose of systematic 

 classification. A well-developed postabdominal respiratory 

 siphon is known to exist in many totally different groups of 

 Dipterous larvae, e.ff., Ptychopteridae, Psychodidae, Culicidae, 

 Stratiomyidse, Phoridae, Eristalinae (Syrphidae), Autho- 

 myidae, Ephydridae, Drosophilidae, and others. 



Being specially interested in the structure of Eristaline 

 larvffi, I have had occasion to examine many examples of 

 this subfamily, and, from my knowledge of their morpho- 

 logy, I am forced to the conclusion that the larvae under 

 consideration have no affinity whatever with the Eristalinae, 



