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REARING LARVAE OF THE CLUSTER FLY, POLLENIA RUDIS 



R. M. DeCoursey, Connecticut State College 



THE larvae of the cluster fly feed upon certain species of earthworms 

 such as Allolobophora chloroticus, A. caliginosa, or Eisenia rosea. 



Copulation of adults occurs in the latter part of February at Urbana, 

 111., and during the early part of March at Storrs, Conn. After copula- 

 tion females may be collected by hand on the sunny side of buildings by 

 placing a test tube over the flies, or they may be caught in traps de- 

 signed for catching houseflies. The best bait for cluster flies is banana. 



Females kept in cages over soil will usually lay eggs on or in the soil. 

 Cages made from lantern globes are convenient. Flies caught early 

 in the spring will often delay ovipositing for two or three weeks. It is 

 necessary to supply food and water during this period. Pieces of banana 

 or apple may be used for food. 



One method of rearing consists of permitting the flies to oviposit on 

 soil in cages known to contain certain species of earthworms. The 1st 

 instar larvae enter the soil, presumably attack the earthworms, and in 

 about 30 days a few may emerge as adults. This method does not 

 enable one to learn much about the habits of the larvae during the various 

 instars. 



Another method is to collect the eggs, placing them on moist blotting 

 paper in a low stender dish with a cover to preserve moisture. The eggs 

 hatch in about three days. A few larvae are transferred to earthworms 

 which are kept on moist filter paper in other stenders with covers. The 

 species of earthworm most commonly used is Allolobophora chloroticus. 

 After the 1st instar larvae attack the earthworm a small amount of rich 

 soil is added to keep the earthworm alive. The larvae usually penetrate 

 through the cuticula at the anterior end of the worm from about the 

 10th segment to a few segments posterior to the clitellum. The clitellum 

 seems to be a favorite point of entry. Most larvae enter from the dorsal 

 side of the earthworm. Under a microscope they may be observed 

 feeding with their posterior spiracles exposed. 



As the larvae grow and pass into later instars they cause greater 

 damage to their hosts. The effect of the larval feeding combined with 

 the unnatural environment often causes the earthworm to die; so several 

 earthworms are ordinarily used in rearing a single larva. Temperatures 

 approaching that of the natural habitat of the earthworm in the soil 



