DIPTERA. 1 1 1 



tended to its fullest length to receive the necessary 

 oxygen from the air. The larvae of some of the Syr- 

 phidae sometimes live in decayed trees. 



The genus Volacella contains some large flies, and is 

 remarkable for the fact that the species belonging to it 

 select the nests of bees, wasps, or hornets, wherein they 

 deposit their eggs. Vollucella pelluce?is (Plate IV., Fig. 9), 

 is a common species, and may be recognised at once by 

 the first segment of the abdomen, which is white and 

 pellucid ; it is a very swift-winged fly, and not very 

 easily captured. The larvie of V. pellucens are parasitic 

 on those of wasps ; the larvae of V, hombylans on those 

 of the bumble-bees ; this latter fly is very similar to a 

 bumble-bee, and no doubt is not recognised by the bees 

 themselves as being a dangerous enemy to their young, 

 or they would not allow it to enter their nest. " Did 

 these intruders venture themselves among the bumble- 

 bees in a less kindred form their lives would probably 

 pay the forfeit of their presumption." (Kirby and Spence). 

 This is quite true of V. homhylans ; but there is no 

 resemblauce between V. pellucens and any kind of wasp. 

 The eggs are laid either in the cell which contains the 

 wasp larva or on the top of the nest ; the larva of 

 Voliicella, when hatched, eats its way into its victim, 

 gradually intruding its whole body except the last 

 segment, on which are the respiratory orifices, which 

 thus come in contact with the external air. 



The insects of the next family, the Conopidoe, frequent 

 flowers, and their larvae, like those of the preceding one, 

 are parasitic on those of the bumble-bees. They are 

 generally slender insects, about half-an-inch long, with 

 the second abdominal segment more or less petiolated. 



