222 



HUBERT M. MORRIS. 



The depth of soil in the jar was not sufficient to show the maximum depth to which 

 the flies would penetrate for the purpose of oviposition, as some of the egg-masses 

 were in contact with the bottom of the jar, 3-5 cm. below the surface. 



After oviposition the flies soon died, usually just outside the cell containing 

 the eggs. 



Eggs. 



The jar containing the soil in which the eggs had been laid was placed in the 

 laboratory, the soil being kept damp. The eggs were observed to hatch in from 

 33 to 35 days after being laid, all those in a mass hatching more or less at the 

 same time. 



The eggs are white when first laid, but soon afterwards darken at both ends. 

 They are almost cylindrical, with rounded extremities, the diameter of one end being 

 slightly greater than that of the other, and they are slightly curved. Their length 

 is from 0-73 mm. to 0-76 mm. ; their chameter at the larger end 0-18 mm., and 

 at the narrower end 0-15 mm. 



The eggs appear rather opalescent owing to their being covered with small 

 projections on the chorion. 



Fig. 2. Newly hatched larva of Bibio marci, lateral view ; setae of 

 right side omitted ; X 65. 



Newly hatched Larva. 



The newly hatched larva (fig. 2) is about 1-6 mm. in total length, the length of 

 the head being about 0-25 mm. The head is relatively large, of a pale yellowish- 

 brown colour, and bears a number of relatively long setae. 



The body is colourless and transparent, the contents of the alimentary canal 

 showing through as a dark line. The body is divided into twelve segments, each 

 bearing a number of long, slender setae. There is, in addition, a much greater 

 number of shorter setae, all the setae arising from enlarged conical bases. 



At this stage the larva bears a single pair of spiracles, which are situated on the 

 twelfth segment, in a corresponding position to that occupied by the spiracles of that 

 segment in the full-grown larva. 



The head and mouth-parts are very similar to those of the full-grown larva. 

 The mandibles are shorter, with relatively longer teeth ; the maxillae are similar 

 to those of the older larva ; the projections at the anterior end of the submentum 

 of the labium are sharper and relatively longer, and there is a median projection 

 between them, which is not present in that of the full-grown larva. 



