539 

 i 



flowers, remaining . for a short time stationary in the air. They 

 bear some resemblance to some species of wasps, with broad yellow 



Syrphus fly. 



Syrphus fly larvae suck- 

 ing out the vital fluids 

 of an aphis. 



Syrphus fly larvae in the act of sucking out an aphis. 



bands across the abdomen. The fly in its matured state is of no 



economic importance. The 

 larvae, however, are very 

 destructive to plant lice. 

 The parent fly lays a single 

 egg among a family of lice, 

 which hatches in a few days, 

 and immediately commences 

 its work of destruction. It- 

 seizes a louse, and holding 

 it aloft while it kicks and 

 struggles, sucks the juice 



from its body, and then casts the empty skin away. These maggots 



are blind and have no distinct feet, but they have no trouble in 



finding a louse by extending the segments of their body, which 



enables them to 



nearly double their 



length, and to 



strike here and 



there until they 



find their prey. 



Laced-winged fly, eggs, 

 and larvae. 



Laced-winged fly. 



Some species of 

 ladybirds are also 

 important factors 

 in the destruction 

 of plant lice, both 



as adults and larvae ; but as they consume the entire louse, they can- 

 not compare with the larvae of the Syrphus flies in the speedy 

 disposal of aphis. A Syrphus fly larvae will dispose of five to seven 

 lice while the ladybird larvae is consuming one. 



