TAILORS 195 



little Hydrocampa had elaborated an outfit that 

 enables it to remain under water for months. It 

 is an air-breather, and it is necessary therefore that 

 its dress should contain a considerable volume of 

 that commodity. This it does by cutting out a 

 piece of leaf of the desired shape and size from the 

 under side of the leaf. This is attached to another 

 part of the leaf by silk threads in such a manner 

 that the two under surfaces are opposed. The 

 reason for this detail is that the leaf is slightly 

 concave beneath, and when the two concavities 

 come together they form a hollow pouch. The 

 second leaf is then cut to correspond with the 

 piece attached to it, so that there is now a lentil- 

 shaped case quite detached from the leaf and 

 available for removal from leaf to leaf. 



In ponds where the yellow water-lily grows as 

 well as Potamogeton, the caterpillar, as the summer 

 advances, transfers its case to the former plant, 

 the more fleshy leaf probably supplying a more 

 suitable pabulum for its increased size. When the 

 caterpillar is full-grown it is about an inch in length. 

 The caterpillar does not feed upon the material 

 of its case, as is done by some other tailors, so the 

 problem to be solved is how to construct the case 

 that it will keep out water and yet permit the 

 caterpillar to put out the fore part of its body for 

 the purposes of feeding and locomotion. At one 

 end of the case the edges are left unsewn for a 

 small space, just sufficient to allow the caterpillar 

 to protrude, but the opening is so contrived that 



