BENEFICIAL INSECTS. 







$r*,ry 

 INTRODUCTORY. 



In their relation to cultivated crops, insects may conveniently 

 be divided into three groups, viz. : 



Pests those which are harmful, causing by their 

 depredations serious loss to the cultivator and a diminution 

 of the country's food supply; 



Neutral or negligible those which do not directly 

 influence crop production ; 



Beneficial those which by predaceous or parasitic 

 habits diminish and keep in check the numbers of the 

 Pests. 



There is some overlapping between these three groups, but 

 it is generally possible to assign an insect to one or the other. 



In considering beneficial insects from the cultivator's point 

 of view, it is only possible to deal with certain large groups, 

 various members of which attack and destroy the worst insect 

 pests to agriculture and horticulture. Of these groups, five are 

 outstanding as amongst the very best friends possessed by the 

 farmer, gardener and fruit-grower : they are Ladybirds, Lacewing 

 Flies, Hover Flies, Ichneumon Flies, and Tachinid Flies. Only*' 

 too frequently these insects are mistaken for foes and destroyed. 

 It is hoped that the brief descriptions of them and short outlines 

 of their life-histories herein given may help towards their wider 

 recognition. 



In connection with all of them one point must first be 

 emphasised : Beneficial insects seldom, if ever, exterminate a 

 pest, or extermination of themselves would be likely to follow. 

 The most they do is so to check the pests (which would other- 

 wise breed in colossal numbers) that the damage suffered by 

 crops is reduced to an almost negligible amount. Their work 

 of destruction goes on unobtrusively, and only fails when some 

 influence favours the pest or acts adversely on the parasite, 

 allowing the former to survive in such overwhelming numbers 

 that an effective control no longer obtains. The cultivator 

 himself must then resort to artificial measures of pest destruc- 

 tion, but in doing so he must remember that he is often killing 

 both friend and foe alike. He must, therefore, having once 

 begun, be prepared to continue his spraying or other measures, 

 and himself carry out the work previously left to Nature. 



LADYBIRDS. 



Ladybirds are beetles which do untold good by feeding in 

 the adult and grub (larval) stages upon Aphides (Greenfly or 

 " Blight "). Some kinds also feed on Scale Insects, Suckers, or 

 other pests. 



r (5)16948 Wt P 2120 R 7 10,000 4/22 



M160927 



