INTRODUCTION. 87 



from food till their task is completed, and if they 

 do not, they may frequently increase the suppleness 

 of the leaf, although we do not allow them credit 

 for being sufficiently sagacious to gnaw its fibres for 

 that express purpose. 



The proceedings of different caterpillars, in forming 

 dwellings of this kind, vary considerably ; but the 

 mechanical means which they employ are in most 

 cases similar to the above. Some roll the leaves 

 from the point down the mid-rib, others from the 

 side towards the centre. Many compose their 

 habitations by rolling two leaves together, while 

 others draw the two sides towards each other and 

 convert the whole leaf into a capacious tube. A 

 few, less laborious than their fellows, select the long 

 and nearly parallel leaves which terminate the 

 young shoots of the willow, and very expeditiously 

 adapt them to their own purposes, simply by wind- 

 ing round them a number of silken cords. Such 

 kinds show a wonderful degree of instinctive fore- 

 sight, in carefully gnawing the bud at the extremity 

 of the shoot, which is enclosed in the centre of the 

 packet, and thereby preventing it from sprouting, as 

 its doing so would have the effect of disarranging 

 the whole tenement, and probably rupturing the 

 bands by which it was held together. A small 

 number take up their abode in the centre of um- 

 belliferous herbs. It is well known, that in many 

 of these plants the little umbels gradually become 

 longer as they recede from the centre, and that 

 consequently when they approyimate to each other, 



