308 Transactions. — Zoology. 



Fig. 11. Sipuncvlus maoricus : piece of the wall of the introvert (seen 

 under a low power), showing the hook-shaped tubercles; with 

 (a) an axial mass of cells. 



Fig. 12. The same : a tubercle in longitudinal section ( X 80). a, axial 

 mass of cells, in continuity with— c, a group of ccelomic cor- 

 puscles ; cm, circular muscles of body-wall ; d, dermis ; 

 gl, epidermal glands ; Im, longitudinal muscles. 



Fig. 13. The same : a portion of surface of body (as seen through a 

 hand-lens) showing the characteristic longitudinal and circular 

 grooves marking out raised rectangular areas. 



Art. XXIII.— The Aquatic Larva of the Fly Ephydra. 



By W. B. Benham, D.Sc, M.A., F.Z.S., &c, Professor of Biology 

 in the University of Otago. 

 [Read before the Otago Institute, 9th August, 1904.1 

 Plate XVII. 

 Amongst the organisms collected by Mr. J. A. Thomson in a 

 saline pool at Barewood, Central Otago, which were submitted 

 to me for identification by Mr. Gr. M. Thomson, were a number 

 of small brown larvae, or rather " puparia," having rather a 

 peculiar form. This larva, which for reasons stated below I 

 ascribe to the Dipteron genus Ephydra, resembles in general 

 form and structure the " rat-tailed " larva of the hover-flies 

 (Helophilus* and Eristalis-f)— in the very reduced condition of 

 the head, in possessing a series of paired groups of claw-shaped 

 spines segmentally arranged along the ventral surface, and in 

 the long posterior respiratory tube or " tail " ; but in the two 

 genera just named this tube is retractile, whereas in the insect 

 herein described it is not retractile, and is, moreover, bifurcated. 

 In looking through the small amount of general literature on 

 the Diptera available here, the only genus of flies that I was able 

 to find in which the larva of this general form of structure has 

 a bifurcated respiratory tube is Ephydra. No doubt a figure of 

 this larva is to be found in one or more recent monographs, or in 

 memoirs published in periodicals concerned with entomology; 

 nevertheless, in the interests of those who are unable to consult 

 these works, if seems to me worth while to present a brief 

 illustrated account, so that naturalists in New Zealand may be 

 able to identify the creature. My identification rests upon the 

 brief accounts contained in Westwood's "Introduction to the 

 Modern Classification of Insects" (1840), and in Packard's 

 " Guide to the Study of Insects " (1872). The former author 



* Hik1m.ii. NX. Entomology, p. 58, pi. vii., fig. 1. 

 + Miall'a Nat. Hist. Aquatic Insects, p. l'.'S ,/ seg. 



