AND HABITS OP THE YELLOW DUNG-FLY. 



639 



other drying factors, it would dry up to a sufficient consistency 

 for the larva to commence living a normal existence buried in the 

 dung itself. 



The Larva. — Second Instar. 



After the first ecdysis the larva increased considerably in size. 

 It measures from four to six millimetres in length. The general 

 shape of the body and the number of segments remain constant 

 throughout larval life. It is now amphipneustic, being provided 

 with an anterior pair of spiracles (text-fig. 8, j) in addition to 

 the posterior pair. The anterior spirncles are situated at the 

 junction of the second and third segments, and will be described 

 in detail in the following instar. The posterior pair are identical 

 with those described in the preceding instar. 



Text-figure 8. 



Larva of S. stercoraria . 2nd instar. 



The locomotory spines on the first segment in the previous 

 instar have now disappeared. Spines similar to those of the first 

 instar but proportionately larger occur on each segment behind 

 the fourth. They are concentrated on the anterior border of the 

 fifth, sixth, and seventh segments, but the area covered increases 

 posteriorly. The last few segments are uniformly covered. 



The first segment is similar to that described previously, but 

 the locomotory spines are absent. Also the two parallel channels 

 converging into the mouth are now replaced by a number of 

 channels radiating from the mouth over the ventral surface of the 

 oral lobes (text-fig. 8, /). 



The chitinised mouth-parts have no similarity with those 



