14 Mr. H. Donisthorpe on 



sets of materials as the others, and I find that they are 

 quite unable to construct a new case, when once they have 

 been removed from their original one. They excrete small 

 particles of a substance similar to that of which the case is 

 made, but they never make any attempt to build a new 

 case. These larvte also lived for months; they were of all 

 sizes, but the full-grown larvaj never pupated, and all died 

 in the end. 



I left cases in water, alcohol, benzine, methylated spirit, 

 vinegar, sulphuric acid, etc., in all of which they are 

 insoluble. The only thing in which they appear to be 

 soluble is caustic potash. Furthermore I sent empty 

 cases to Professor Poulton to experiment with. He 

 kindly reports as follows : " Heated in the blue flame of a 

 Bunsen burner, the cases first gave off a smoke and then 

 burnt with a bright flame. This was probably the decom- 

 position and removal of some cement substance and 

 colouring matter secreted by the larva. Keeping the case 

 at incandescence for some minutes, there remained a pale 

 reddish-brown cast, exactly similar to the original case. 

 It was friable, and easily ground to powder by pressure. 

 This powder, examined in a drop of water under the 

 microscope, was seen to consist of transparent crystalline 

 masses of very variable size and irregular outline. They 

 were unaffected by strong hydrochloric acid, and are pro- 

 bably minute fragments of quartz. The cases are probably 

 made of an earth chiefly composed of a quartz sand, and 

 cemented together by some secretion of the larva's. The 

 reddish tint was probably caused by sesquioxide of iron, 

 derived from iron in the earth made use of." These ex- 

 periments confirm the fact that the larva constructs its 

 case of earth, mixed with its excrement as a cement. We 

 can see the inipcjrtancc of the cases being insoluble in 

 acid since the ants squirt formic acid on to them. 



Fabre says, speaking of species of Gryptocephalus and 

 Clythra, that they enlarge the case by removmg the old 

 material from within, and plastering it on the outside, and 

 that they construct the case with their excrement mixed 

 with earthy material, using only the mandibles for the 

 purpose. It is stated that when the larva changes its skin 

 it first fastens its case to a piece of wood or other object 

 in the nest. I have found that some of the larvae in my 

 nest fastened themselves to a small piece of Avood for a 

 day or two (when I thought they were going to pupate), 



