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Life-History of a Bee- Fly. 



217 



4. Larva (Fig. 5). 

 Young larvae are most commonly found singly on the 

 ventral side of the thorax of host larvae of the third instar, 

 where they cling between the legs. No second instars have 

 been found with parasites. While in the position between the 

 legs they cannot be reached by the host and do not come 

 readily into contact with the sides of its burrow. There are 

 however frequent exceptions to this, for host larvae not infre- 

 quently have more than one larva between the legs or single larvae 

 on other parts of the body. One host larva had in addition to 

 the parasite on the ventral side of the throax, two others on the 

 posterior third of the abdomen. Attempts to secure eggs or 

 young larvae from sand gathered from the edges of burrows 

 about which eggs had been laid or to rear larva from eggs 

 squeezed from a laying female, have failed. Neither have we 



Figures 4-10. Early larval stages of Spogostylum anale Say. 

 Fig. 4. The egg; enlarged about five diameters. 

 Fig. 5. A young larva of the second stage; about five times natural size, in a 



somehwat curved position. 

 Fig. 6. The same in position enlarged about nine times. 

 Fig. 7. At the time of moving to the abdomen; enlarged about five times. The 



larva has withdrawn its anterior half from the old integument. 

 Fig. 8. The larva in position in the thorax, showing the ring of thickened 



chitin(r) in the integument of the host and the long slender mandibles 



in position. 

 Fig. 9. The larva after one day on the abdomen of the host: about five times 



natural size. 

 Fig. 10. The larva at the end of the second day upon the abdomen. 



