272 [June, 1892. 



being given to it, and the terminal valves added, until the form and 

 almost the size of the mature ease are reached. The anal end, how- 

 ever, still remains closed, and the walls thin and weak, and though the 

 case can afford a fairly serviceable covering if the larva be obliged to 

 move, yet the latter usually prefers to keep it fixed to the old moorings, 

 whilst he himself goes in search of food within the rush-head, which 

 is now riddled and honeycombed by the family burrowings. That he 

 sometimes comes to grief in these excursions, or fails to find his way 

 back again and has to build afresh, seems warranted by the fact that 

 empty cases are not unfrequently left stranded on the rush-heads long 

 after the full ones have been carried off by their owners into winter 

 quarters. Many of these empty cases are. of full size, but whiter 

 than they should be, and invariably have the anal orifice closed. The 

 last step in the process of manufacture is the permanent unsealing of 

 the anal orifice, and the strengthening of the walls, not, I think, by 

 further spinning, but by the infiltration of some more liquid material, 

 which, like the size of the calico-manufacturer, effectually stiffens 

 them, and at the same time changes their colour from w^hite to pale 

 ochreous or buff. As for the origin of the stiffeniiio- material : it is 

 not reasonable to suppose that the same gland can supply one kind of 

 product at one time and quite a different kino - "another, so that we 

 must look elsewhere than to the silk gland tor its source. Now, it 

 seems to me, for reasons I need not enter into, highly probable that 

 this source is the so-called salivary glands, and I would suggest that 

 the function of these organs is not to aid in digestion, as is commonly 

 supposed, but is rather connected with the above phase of larval 

 economy.* The case being now complete, the larva henceforth, I 

 believe, resides permanently within it. 



C. GLAUCICOLELLA. 



Exp. al., 5 — Sj lin. Fore-wings shining greyish-ochreous, unstreaked, though 

 frequently with a few (generally four) obscure dark dashes running into the apical 

 half of the costa. Costa conspicuously white, shading gradually into the whitish- 

 ochreous fringe at the apex. Antennse annulated with grey on the inner face, the 

 outer face and tip entirely white j occasionally in the $ both faces are white. 



■ These glands appear to be present in most, if not all, the insect orders, and I venture to 

 think that their office is in every instance connected with some process or other external to the 

 body. Thus, 1 believe these glands in the Hemiptera instil an irritating fluid into the puncture 

 made by the proboscis in the leaf or other living structure, and so bring an increased flow of sap 

 to the spot. Again, the pain and swelling caused by the bite of gnats, &c., are clear proof that 

 they introduce some irritant or poison, and what more likely than that it is the product of these 

 glands. Then w^e know that bees and wasps make use of an adhesive fluid for working up the 

 material of their nests, or for kneading the excavated soil that it may be more easily carried 

 away, and I doubt not that in their case also this substance is secreted by the so-called salivary 

 glands. 



