structure that it will prey upon. It apparently never makes, 

 a mistake, but how it knows amongst the diverse insects met 

 with which are suitable to it and which are not is still somewhat 

 of a mystery. 



TACfflNID FLIES. 



Though Tachinid Flies (Plate I., Fig. 5) do immense good 

 in destroying caterpillars, it would be serving no useful purpose 

 to deal with them fully with a view to preventing their destruc- 

 tion, for they can only be recognised by the expert entomologist. 

 Superficially, they are much like the common House-Fly, an 

 appearance which is also shared by several other flies which are 

 troublesome pests. Many species of Tachinid Flies are larger 

 than the House-Fly. A close examination of all would show them 

 to be covered with strong bristles. Their habits are akin to 

 those of the Ichneumon Flies , but the egg or eggs are deposited 

 either upon the skin of the grub they attack or upon its food 

 plant. The resulting maggots eat their way into the interior 

 of the creature and feed there, or possibly in certain cases the 

 Tachinid eggs may be eaten by the grub with its food, and 

 reach its body in that way. The grubs feed within the bodies 

 of their hosts. On becoming full-fed they eat their way out 

 and form a puparia, very much like those of the House-Fly, 

 and on emerging from them the flies again deposit their eggs. 



These insects are true flies, not like the Ichneumons, which 

 are related to the bees. They possess but two wings, and the 

 mouth is formed for sucking. 



HOVER FLIES. 



Syrphid Flies, or Hover Flies as they are also called, belong 

 to the true flies, though many present a somewhat close super- 

 ficial likeness to certain bees and wasps. They, nevertheless, 

 have but two wings and sucking mouths, the main character- 

 istics of their whole Order. The Syrphid group is a large one 

 which comprises some pests (e.g.., the Narcissus Flies), many 

 kinds which are neutral, and a number which are beneficial to 

 a high degree. 



The grubs of the latter, together with the Ladybird and 

 the Lacewing, comprise a trio of voracious devourers of Aphides 

 or Greenfly, and are frequently found in company. There is 

 little danger of the very active-winged adult falh'ng a victim 

 to the destroying hand or foot, though undoubtedly the mis- 

 guided zeal of the gardener only too often finds vent against 

 his good friend in the grub or maggot stage. 



Description and Life-History. The Egg of the Syrphid Fly 

 is cylindrical and pale yellow in colour. It is deposited amongst 

 Aphides on the stem or leaf of a plant. 



The Grub (Plate II., Fig. 2) is an unprepossessing-looking 

 maggot, dirty-white or greenish in colour, more pointed at the 



