302 THE WONDERS OF INSTINCT 



digests : the supreme felicity of an animal which is little 

 more than an intestine. There is never a distraction, 

 unless it be certain see-saw movements which are par- 

 ticularly curious when several caterpillars are grazing 

 side by side, abreast. Then, at intervals, all the heads 

 in the row are briskly lifted and as briskly lowered, time 

 after time, with an automatic precision worthy of a 

 Prussian drill-ground. Can it be their method of intim- 

 idating an always possible aggressor ? Can it be a man- 

 ifestation of gaiety, when the wanton sun warms their 

 full paunches? Whether sign of fear or sign of bliss, 

 this is the only exercise that the gluttons allow themselves 

 until the proper degree of plumpness is attained. 



After a month's grazing, the voracious appetite of 

 my caged herd is assuaged. The caterpillars climb the 

 trelliswork in every direction, walk about anyhow, with 

 their forepart raised and searching space. Here and 

 there, as they pass, the swaying herd put forth a thread. 

 They wander restlessly, anxiously to travel afar. The 

 exodus now prevented by the trellised enclosure I once 

 saw under excellent conditions. At the advent of the 

 cold weather, I had placed a few cabbage stalks, covered 

 with caterpillars, in a small greenhouse. Those who 

 saw the common kitchen vegetable sumptuously lodged 

 under glass, in the company of the pelargonium and the 

 Chinese primrose, were astonished at my curious fancy. 

 I let them smile. I had my plans : I wanted to find out 

 how the family of the Large White Butterfly behaves 

 when the cold weather sets in. Things happened just 

 as I wished. At the end of November, the caterpillars, 



