And habits of the yellow dung-fly. 



637 



A number of newly hatched larvae perish through not getting in 

 before they starve. 



The Larva. — First Instar. 



The larva immediately after hatching measures from 2 to 

 3 mm. in length. The body is cylindrical, composed of twelve 

 segments, and generally tapers to a point at the anterior end. 

 The posterior end is truncate, forming the anal plate. In this 

 stage the larva is metapneustic, the two spiracles being placed 

 side by side on the anal j^late. Each consists of a chitinised ring, 

 situated on a pair of short projections from the anal plate, en- 

 closing two slit-like apertures. The anal plnte is bordered by a 

 number of tubercles, the position of which will be described in 

 a later instar. 



The first four segments are devoid of spines. Yery delica.te 

 spines occur on the anterior border of each segment from the 

 fifth posteriorly. The area covered on each segment increases 

 proceeding posteriorly, the whole surface of the last two segments 

 being uniformly covered. 



Text-figure 6. 



Larva of S. stercoraria. 1st instar. 



The first segment is divided dorso-ventrally by a cleft forming 

 the two oral lobes (text-fig. 6, /*). Each lobe carries a pair of 

 sense tubercles (text-fig, 6, i). In addition, the ventral surface 

 of the first segment is provided with a transverse row of strong 

 backwardly-curved spines (text-fig. 6, e). These are locomotory 

 in function. Keilin mentions them as being present in the 

 first instar larv'a of Musca assimilis. Below the spines there are 

 two channels running more or less parallel with each other. They 

 originate at the mouth, and run out laterally over the ventral 

 surface of the first segment. They are fringed with hair, and 

 direct the liquid food towards the mouth (text-fig. 6,/). 



