125 



ON A SINGULAR CADDIS-WORM CASE FROM CEYLON. 

 BY R. M'LACKLAN, F.L.S. 



In the extensive collection of the Cases of Caddis-worms, both 

 British and exotic, in the Collection of the British Musexim, I find two 

 from Ceylon evidently belonging to the same species, of forms so sin- 

 gular, that I think a short notice of theii' peculiarities cannot fail to be 

 interesting to Entomologists generally. Owing to the assiduous 

 researches of Mr. Nietner we know more of the Trichopterous fauna 

 of Ceylon than of any other tropical country, but it is of course 

 impossible to say if these cases belong to any of the species brought 

 over by him. There can be little doubt that they belong to some insect 

 of the family Leptoceridce, which family is represented by several species 

 of Setodes in Mr. Nietner's collection. 



The form of the largest of the cases is as follows. To the upper 



end of a straight cylindrical tube 

 tapering gradually to a point, and 

 with an even and nearly circular mouth, 

 is affixed a large, nearly round shield, 

 concave below and convex above ; 

 viewed from above the shield and tube 

 are insej^arable, but beneath the latter 

 appears as a separate portion, its upper 

 or mouth-end extending to near the 

 middle of the shield. The case 

 ^ is constructed of fine grains of sand 



cemented together by, and coated over with, some peculiar sub- 

 stance, probably a secretion of the larva. The edges of the shield 

 are a little irregular. The whole case has the form of a Torpedo in 

 miniature. The length on the upper-side, from the extreme end to the 

 anterior edge of the shield, is 10 lines ; the breadth of the shield at its 

 broadest part 4^ lines ; and the length of the tube, from the mouth 

 to the apex, 6| lines. 



In the smaller specimen (fig. 3) the shield is imperfectly developed 

 and somewhat reniform. This may be the usual condition of the case 

 in immature examples, or perhaps the form of the shield is liable to 

 variation independent of age. This case has a minute opening at the 

 small end, which is not visible in the larger one, being perhaps closed 

 by the inhabitant, or by accidental pressure. 



These structures form beautiful illustratious of the different modes 

 in which the habits of insects are adapted to the conditions in which 



