61 



the hunters, who are in turn furnished with a most wonderful apparatus, 

 known as the ovipositor; it is formed of several parts, all used in pricking 

 the skin of the victim and when depositing eggs in the living host ; the shape 

 and structure of this ovipositor often tells the naturalist what kind of 

 insect he may expect to find its possessor attacking. Some little parasitic 

 wasps that lay their eggs upon the active leaf hopper, which they first have 

 to catch and then hold, have remarkable pincer-like processes upon their legs 

 by which they are enabled to accomplish this without any difficulty. 



Another important factor in the sole control of pests with useful insects is 

 that the latter cannot eat up all their food supply, or else they in turn would 

 die out, while if they leave even a small percentage in the orchard (in 

 particular) their value is very much discounted. 



Again, in a time of short commons the ladybird beetles and their larvae 

 eat their weaker brothers .and even their own eggs, and the savage little 

 larvje of the lace wings eat friend and foe without any discrimination. 

 Several instances have been recorded of introduced useful insects which, 

 having left what was their natural food in their own home, have turned their 

 attention to the larvae of a native useful insect. An introduced hymenopterous 

 parasite did a great deal of damage to one of the native ladybird beetles in 

 America some years ago by parasitising its pupa\ 



Changes of climate make an immense difference to insects ; and thousands 

 of parasites have been forwarded from temperate climates to semi-tropical 

 countries, with the result that, though surrounded with food when liberated, 

 they have wandered away and died. This was the case with large quantities 

 of ladybird beetles that we sent to India arid Ceylon some years ago ; there 

 was plenty of food for them, but they never became acclimatised, so the 

 experiment was dropped, and other means were taken by the tea and coffee 

 planters. 



Again, nearly every species of ladybird beetle has its own particular kind 

 of food ; some only touch mealy bugs, others aphis, while many that live 

 among foliage infested with hard scales have not the power to turn over the 

 Lard shield or to bite through it, though they greedily devour the armoured 

 scale if it is turned over for them. Their food is the young larva) when 

 they emerge from the protective parent scale under which they have been 

 hatched. 



It has also been the habit to credit the introduced insect with all the dead 

 scale upon the infested plant, whereas we always find on a badly-infested 

 tree a large percentage of dead scales that have died or remained undeveloped 

 from many oth^r C The native useful insects, perhaps more numerous 



than the intro luced ones and often quite as active. aiv ignored in the glowing 

 and usually exaggerated accounts given by the parasite introducer. No\\. if 

 I'-tion of the ladybird beetles is so doubtful and variable, and there is no 

 disputing th- il must be quite evident to the reasonable man that the 



fluctuations and changes in the life of minute hymenopterous and dipterous 

 para^it's must be very much more complex, and their establishment in a new 

 country v. ry difficult, for every parasite has an enemy as well as the other 

 insect. Li fa-.-t, if the entomologist lakes up the breeding out or the minute 

 cirnivorous and plant-eating insects found in galls and in the remains of other 

 insects, it is often a work of givat dilHcultv, even for th" expert, to say which 

 is the true parasite, iiujualine or the hyper parasite. 



Let this internal p;i. effective, so that it increases and multiplies 



until it has destroyed all the pest, then it must either die out or find fresh 

 food supplies ; if it is not thorough in its work, it is of no commercial value. 



