INTELLiaENCE OF LAKV^— CATEKPILLAKS. 237 



Oommon cabbage caterpillar, whicli, when building web under 

 stone or wooden surfaces, previously covers a space with a web 

 to form a base for supporting its dependent pupa, when building 

 a web beneath a muslin surface dispenses with this base 

 altogether : it perceives that the woven texture of the muslin 

 forms facilities for attaching the threads of the cocoon securely 

 enough to support the weight of the cocoon without the neces- 

 sity of making the usual square inch or so of basal support.^ 



The instincts of the larva of the Tinea moth are thus 

 •described by Keaumur : — 



It feeds upon the elm, using the leaves both as food and 

 <5lothing. To do this it only eats the parenchyma of the leaf, 

 preserving the upper and under epidermal membranes, between 

 -vvrhich it then insinuates itself as it progressively devours the 

 parenchyma. It, however, carefully avoids separating these 

 membranes where they unite at the extreme edge of the leaf, 

 which is designed to form ' one of the seams of its coat.' The 

 cavity when thus excavated between the two epidermal mem- 

 branes is then lined with silk, made cylindrical in shape, cut off 

 ;at the two ends and all along the side remote from the * seam,' 

 and then the two epidermal membranes sewn together along the 

 side where they have had to be cut in order to separate them 

 from the tree. The larva now has a coat exactly fitting its body, 

 and open at each end. By the one opening it feeds, and by the 

 other discharges its excrement, ' having on one side a nicely 

 jointed seam — that which is commonly applied to its back — 

 composed of the natural marginal junction of the membranes 

 of the leaf.' 



Eeaumur cut off the edge of a newly finished coat, so 

 as to expose the body of the larva at that point. The 

 animal did not set about making a new coat ab initio, as 

 we might expect that it would on the popular supposition 

 that a train of instinctive actions is always as mechanical 

 as the running down of a set of cog-wheels, and that 

 wherever a novel element is introduced the machinery 

 must be thrown out of gear, so that it cannot meet a new 

 emergency of however simple a character, and must there- 

 fore re-start the whole process over again from the be- 

 ginning. In this case the larva sewed up the rent ; and 

 not only so, but ' the scissors having cut off one of the 

 projections intended to enter into the construction of 



» Ibid., p. 475. 



