1875.] 161 



of water, I found amongst them a cylindrical case formed witli pieces of Butomus 

 umbellafiis, about an inch and a half long, and half-an-inch in diameter, no doubt 

 originally constructed by a very different aquatic larva, though now tenanted by a 

 laiTa of stratiotalis ; this, on looking at it three hours afterwards, at night, I saw 

 had been deserted ; the next morning I found it again in possession of one of the 

 larvfp, when, for better obserFation, I transferred it with the larva to a wide-mouthed 

 bottle of water and a spray or two of the food-plant ; I also placed four others of 

 the larvre, separately, with pieces of the weed, into as many similar bottles of water : 

 in course of the same evening I saw that the individual in the case had contrived to 

 sink its abode to the bottom of the bottle, and had fixed it there in a nearly perpen- 

 dicular position, by spinning a quantity of silken threads to the end of a stem of the 

 food-plant, already made fast by similar means to the side and bottom of the bottle ; 

 tliis case had previously been floating on the surface of the water, both when empty 

 and when a larva was inside. Another larva that had its bottle supplied with a 

 longer spray bent double, began at once to spin a quantity of silk to the bent part 

 of the stem, and to the side and bottom of the bottle, thus forming a kind of silken 

 tent open at one side, and through this opening I was able to observe all its move- 

 ments from time to time. Another spun for itself a sloping wall or screen of silk, 

 from the side to the middle of the bottom of the bottle, enclosing two pieces of the 

 water-weed fixed witliin it ; tliis was also open at one end. Another spun two stems 

 to the side of its bottle in nearly a vertical position, about half-an-inch apart, and 

 spread its web from one stem to tlie other, and upon the glass of the sides of the 

 bottle, leaving an opening below half-an-inch from the bottom of the water, the top 

 of the web being about the same distance from the top of the water ; this larva 

 continued to live in a position perpendicular to the bottom of the bottle, and even- 

 tually drew the stems of its food closer together, and spun itself up in a cocoon 

 between them on July 25th. 



The fifth larva, which was smaller than the others, spun a squarish web for 

 itself in the midst of three pieces of the water-weed, and, when other pieces were 

 supplied, spun a fresh web amongst them. 



I soon found that these larva; in the bottles, as well as those in the globe, pre- 

 ferred to live at some depth in the water, not one of them choosing to reside at the 

 surface ; each larva in tlie globe- spun a web for itself, either a kind of open tent or 

 a short gallery, aiid the form varied with its surrounding circumstances, but it was 

 invariably fastened to the food-plant, and occasionally to tlie glass also : one larva, I 

 noticed, often cut off leaves from the stem of its food, and tlien attached them to 

 tlie silken wall of its dwelling. 



I now come to mention the peculiar habit of this larva which I watched with 

 extreme interest during many months. 



Kight and day, at intervals varying from one to three minutes apart, the larva, 

 liolding to its web by the anal legs, rapidly undidates its body upwards and forwards 

 with considerable vigour and energy, while the three hinder segments appear motion- 

 less ; this intermittent movement lasts al)Out twenty-one seconds at a time, and is 

 followed by a period of rest— longer, tliat is for two or three minutes — when the 

 larva is quiet, and shorter when it is fei'ding, at such times not exceeding one miiuite. 

 U hat this energetic uiuUilat ion is connected witli tlie respiration of the larva is evident 



