1887.] 201 



ON THE CASES, &c., OF OXTETEIRA COSTALIS, CUET., AND 

 ANOTHER OP THE SYDROPTILID^. 



BY KENNETH J. MORTON. 



At page 17 of the present volume, Mr. McLachlfin has recorded 

 the breeding of Oxyethira costalis, Curt., and in a few words sketched 

 the more salient characters of its interesting case. He then suggested 

 that I should give further details from materials which he had kindly 

 sent me on more than one occasion. I shall endeavour to do so now ; 

 and I take the present opportunity to call attention to another 

 Hydroptilid case communicated by him, which, I believe, also came 

 originally from Mr. Bolton, of Birmingham. 



The transparency of the case of 0. costalis has been noticed. It 

 is so perfectly hyaline, that sometimes the larva appears as if crawling 

 about without any case at all, until suddenly some change of position 

 brings it iiito view, but this colourless transparency becomes slightly 

 lessened with age, as extraneous matter gets attached to the sides. 

 Speaking broadly, the case may be called wedge-shaped, or triangular 

 in contour. In the place of what would be the extreme thin end of 

 the wedge there is a circular opening with everted margin, the mouth- 

 end of the case ; this part is apparently of firm consistency, and firm 

 seams run along the two sides of the triangle. From the mouth back- 

 wards the walls become more and more compressed, until towards the 

 posterior end they meet, and apparently unite in the middle, but 

 remain open at either side in a valve-like slit. This cui'ious structure 

 appears to be altogether composed of the larva's silken secretion ; 

 when seen with a i-inch objective, multitudes of small oval bodies 

 (diatoms) are found to be present, but I am uncertain whether these 

 are actually incorporated with the substance of the case, or simply 

 casually adherent to its outer and inner surfaces. The length is 

 2-| mm. ; breadth at tail end 1 \ mm. ; this example is not quite of 

 full size. 



The larva carries the case with the flat posterior end perpendi- 

 cular to the surface over which it is moving. It spins web freely, and 

 soon fills a small vessel full of fine threads, along which it wanders 

 about. The head of the larva is rather large in proportion to the size 

 of the three ti-ansverse chitinous thoracic segments, and is provided 

 with well develo^Ded antennae ; the two posterior pairs of legs are long, 

 with very long and slender tarsal claws ; and the body is of the usual 

 obese Hydroptilid form. 



Fritz Miiller's description of the case of Lagenopsyclte, a Brazilian 



