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THE LARVAL AND PUPAL STAGES OF THE BIBIONIDAE. 



By Hubert M. Morris, M.Sc, F.E.S. 



Entomological Department, Institute of Plant Pathology, Rothamsted Experimental 



Station, Harpenden. 



Several species of Bibionidae are very common in the adult state during the 

 spring and early summer in Britain, but their larvae seem to have been very little 

 studied. The latter frequently occur in large numbers together, and are from time 

 to time reported to have caused damage to various crops. 



Probably the commonest species of Bibio are B. marci and B. johannis, but 

 several others are also ver}^ frequently met with. The life-history of Bibio johannis, 

 L., has been fully dealt with previously (6), and in the present paper it is proposed 

 to give some account of the life-histories of Bibio marci, L., B. lacteipennis. Ztt., 

 and B. venosus, Mg. 



I am greatly indebted to Dr. A. D. Imms for suggestions and advice during the 

 course of this work, and for the material of Bibio venosus, and to Mr. F. W. Edwards 

 for identifying the adults which have been reared. 



Bibio marci, L. 



Ot'iposition. 



In the early part of May 1920, a number of adults of Bibio marci, of both 

 sexes, were captured and placed in a glass jar, the top of which was covered with gauze. 



Fig. 1. Eggs of Bihio marci, x 6. 



At the bottom of the jar a layer about 3 cm. in depth of fine damp soil was placed 

 The flies were fed on sweetened water, and by this means it was found possible to 

 induce the females to oviposit. After a day or two, the time probably varying 

 with their age when captured, females were seen making their way into the soil. 

 This is accomplished almost entirely by means of the fore legs, which are moved 

 up and down in front of the head, with their tarsi bent back, the actual pressing 

 back of the soil being done by the distal ends of the tibiae. In this manner a 

 burrow just large enough to contain the fly is made, the insect turning over from 

 time to time so that the soil is pressed aside in all directions. The burrows have a 

 very irregular course, but the flies gradually make their way "downwards into 

 the soil. 



At a little distance below the surface, the depth varying in different cases, a small 

 cell is constructed which is of greater diameter than the burrow, and in this cell a 

 mass of eggs is deposited, the eggs being arranged in an orderly manner (fig. 1). 

 (4183) R 



