THE MAGPIE MOTH AND ITS PARASITES 1107 



ever an organism outstrips 

 its natural foes, and be- 

 comes too dominant in the 

 struggle for existence, new 

 enemies arise to check its 

 ra\'ages and restore the 

 lost balance of power. So 

 it occurs that, althout^'h in 

 some seasons we may tind 

 the leaves of currant, 

 gooseberry, or plum trees 

 being destroyed by in- 

 numerable larvae of the 

 Magpie Moth, it does not 

 follow that there will be 

 numerous moths later in 

 the season, and that the 

 pest will thrive and be- 

 come still more abundant 

 the follo\\ing season. Prob- 

 ably b}' the time the moths 

 should have de\'eloped. 

 Nature will have taken 

 measures to correct the de- 

 fect in her working scheme 

 that has allowed an organ- 

 ism too decided preponder 

 ance, and will have checked 

 it so thoroughly that, dur- 

 ing the season that follows, 

 the predominant species 

 may become quite scarce. 

 We will now, then, observe 

 how any excessive dex'elop- 

 ment of the Magpie Moth 

 is suppressed. 



Last autumn in the 

 writer's garden some goose- 

 berry bushes were badly 

 attacked by the larvae of 

 the Magpie Moth, and the caterpillars fed 

 boldly in the bright sunlight, in their 

 characteristic manner. Now, one could 

 not a])proach these bushes during sun- 

 light without finding swarms of what were 

 ap])arently common house-flies buzzing 

 round and congregating about the branches 

 and amongst the leaves. This fact led to 

 an experiment. 



Some of the full-fed caterpillars were 

 collected up and ])rovidefl with some 

 dried stems (m which to form their cocoons. 

 In the upper ])art of p. 1108 two of the 

 larvie are shown in their delicate silken 

 cocoons, in which, when they have 

 moulted their skins, they change to the 



FULL GROWN CATERPILLARS OF THE MAGPIE MOTH AMONGST 

 GOOSEBERRY BRANCHES. 



pu])a or chrysalis stage ; while below, on 

 the right, another has completed its 

 change into a chrysalis, its shrunken cater- 

 pillar skin being seen near it. In the 

 lower part of the photograph on the left 

 is seen another cocoon in which appears 

 the shrunken skin of a caterpillar and 

 three comparatively small chrysalides of 

 oval form. 



The chrysalis of this moth is banded 

 black and yellow, and probably, like both 

 the caterpillar and the mt)th. it derives 

 protection from its bold colouring ; in- 

 deed, the very frail character of the cocoon, 

 in which the chrysalis is clearly t.'X])osed 

 to view, points to that conclusion. 



