332 



Beneficial Insects. 



agreeable odour. It appears at the end of May and deposits 

 eggs on the plants. The white eggs are laid in groups of 

 seven to nine on leaves, or upon twigs or stalks, each egg 

 being placed upon a footstalk with a thread about half an 

 inch long. From the egg the larva appears in seven or eight 

 days and at once begins to devour the aphides near. It is 

 slate coloured, with red marks on it, nearly the fourth of an 

 inch long, and covered with tufts of hair, having a long 

 flexible neck and strong hooked jaws. It remains in this 

 stage for about fifteen days, and changes to a pupa in a spun 

 cocoon about the size and shape of a sweet pea. There are 

 several generations during the year, if food abounds and 

 other conditions are favourable, and hibernation takes place 

 in the pupal stage upon twigs and stems of trees and plants. 



It has been noticed that the larvae of this fly are great 

 destroyers of the apple- sucker [Psylla viali), which does so 

 much harm, as well as of the apple aphis [Aphis inali\ and 

 the flies may be seen upon apple-trees in the spring and 

 summer months, while the larva can be discovered on 

 the leaves and blossoms, clearing them of the pests which 

 infest them. The larvae have also been frequently seen upon 

 swedes infested with aphides, as well as on hop-plants and 

 currant-bushes, and like the Syrphus larva they do not 

 appear to be particular as to the species of aphis they eat. 



Ichneumon Flies. 



There are many species of ichneumon flies, belonging to 

 several families of the order Hymenoptera, which do great 

 service by placing their eggs either in the larvae or the pupae 

 of many species of insects injurious to farm and garden 

 crops. These flies are generally brilliant in colour, with 

 iridescent wings, and/rom the fourth to the sixth of an inch 

 long. The larvae or maggots which come from the eggs feed 

 upon their hosts and destroy them. Thus the troublesome 

 aphides, besides the other enemies that have been described 

 above, are frequently infested by several species of the genus 

 AphidiuSy whose larvae completely scoop out the insides of 



