I88-J.] 7 



know attacks tLem as soon as, from excess of rain or humidity, they 

 become sickly ; the other by permitting the continued activity of pre- 

 daceous creatures. These are very numerous. Moles continue at 

 work in mild winters, instead of burying themselves deep in the 

 ground ; and mice are constantly active. These small mammalia destroy 

 great numbers of Lepidopterous pupae, and they abound in this dis- 

 trict, as also do birds during the winter in an extraordinary degree. 

 As soon as severe cold sets in to the north and east, the birds come 

 down in swarms to the open fields and sheltered hill sides of this 

 district, and it is hardly necessary to point them out as most indus- 

 trious and persevering destroyers of larvae. Predaceous beetles and 

 earwigs are generally on the alert all through very mild winters, and 

 although they probably do not eat much at that time, and, indeed, are 

 not very plentiful in Pembrokeshire, they must destroy many larvae 

 and pupae, having little else to subsist upon. But I believe that the 

 mischief done by all these added together does not equal that done by 

 the Onisci. 



During mild winters these crustaceous vermin increase and mul- 

 tiply, and feed, and grow without check, till in so mild a climate they 

 become a perfect nuisance, pervading everything indoors and out. It 

 was hardly possible to keep them even out of the breeding cages, where 

 they would get introduced when very small and unnoticed — or perhaps 

 in the egg-state — hunt out and destroy every larva and pupa, and 

 grow large and plump without ever showing themselves above the 

 leaves and rubbish. Doubtless, their industry out of doors was in the 

 same proportion, and my impression is that they approached very near 

 to completely exterminating many species that would naturally be 

 common here. Severe cold seems to destroy some of them, for they 

 are not nearly so numerous now, and it certainly puts a complete 

 stop to their destructive operations during a time when larvae are 

 most especially helpless and liable to attack. To this, with other 

 I causes already mentioned, I am inclined to attribute the extraordinary 

 incrciise in numbers of so many species during the last three seasons, 

 divided by severe winters. The winter now past has been mild, and, 

 therefore, a further progressive increase cannot reasonably be ex- 

 pected ; but I hope that the mischief done in one mild winter may not 

 be serious. It is the progressive increase of destroyers with the de- 

 crease of victims through successive mild seasons that is really to be 

 dreaded. 



As a slight corroboration of this view, I may mention, that while 

 this district of country is comparatively poor in all the species of 



