82 BRITISH BUTTERFLIES. 



frequently found in groups on walls and palings, are 

 the cocoons of these useful little flies, spun round 

 about and over the remains of the dead caterpillar 

 their victim. "These," as Mr. Westwood observes, 

 "ignorant persons mistake for the eggs of the cater- 

 pillar, and destroy; thus foolishly killing their bene- 

 factors." 



Happily these devastating caterpillars have plenty of 

 enemies to prevent their continued multiplication, and 

 to reduce their number speedily when it exceeds certain 

 limits. Besides the ichneumons, mentioned above, the 

 feathered tribes do much towards keeping them down. 

 Mr. Haworth, in his " Lepidoptera Britannica" says, 

 with reference to this : " Small birds destroy incredible 

 numbers of them as food, and should be encouraged. 

 I once observed a titmouse (Parus major] take five or 

 six large ones to its nest in a very few minutes. In 

 enclosed gardens sea-gulls, with their wings cut, are of 

 infinite service. I had one eight years, which was at 

 last killed by accident, that lived entirely all the while 

 upon the insects, slugs, and worms which he found in 

 the garden." 



The pretty egg of this butterfly is figured on Plate 

 II. fig. 1 : it may be found commonly enough, with 

 a little searching, on cabbage-leaves, either at the end 

 of May or beginning of August. 



The caterpillar, which, besides cabbages, consumes 

 various other cruciferous plants, also Tropaeolurns, or, 

 as they are erroneously called, "Nasturtiums/' is green, 



