CH. IX PESTS 161 



when present, and there will not, I think, be much 

 trouble about their identification. 



The keeping the plants in vigorous health is the 

 first preventive measure, for it seems undoubted that 

 aphides, the scale insect, and red spider show a 

 partiality in their attacks for plants which are in a 

 weak and sickly condition. Against all caterpillar 

 and grub depredations, late pruning, after the plants 

 have burst into leaf, is the only prevention that I 

 know of : when this measure has been found necessary 

 through the earliness of the season, a considerable 

 diminution is found in caterpillar numbers ; and it is 

 plain that in such cases the parent insects have laid 

 their eggs on the bursting buds at the top of the 

 shoots, and that all have been happily swept away at 

 the pruning. 



I was surprised on first looking into the matter to 

 find that most of the common caterpillars or grubs 

 which haunt and injure the Eose are the larvae of 

 moths. We sometimes see a good many flies of 

 different sorts and sizes about our Eose shoots on 

 sunny days in April and May, but rarely moths, 

 though there may be, later on, several moth grubs 

 on every plant. The reason of this would probably 

 be that the parent moths visit the plants only at 

 night or at all events in the dusk, and that they are 

 mostly small, insignificant, fluttering insects of the 

 most harmless appearance, and likely in general to be 

 unnoticed. 



Among the flies we may perhaps notice some active 

 creatures, less than half an inch long, looking some- 

 thing like slender-bodied long-legged ants, with 

 iridescent wings ; these will be saw-flies, the parents 

 of very hurtful grubs, and each one caught will 



M 



