no 



Comparisons of cephaloskeletons of Ophyva aenescens and I'tusca 

 domestica . It was determined by Keilin and Tate (1930) that a correla- 

 tion exists between certain anatomical structures of fly larvae and 

 their modes of life. In order to gain further knowledge of the feeding 

 habits of 0. aenescens and M. domestica larvae through the use of ana- 

 tomical evidence, the cephaloskeletons of third-instar larvae were 

 dissected and mounted on microscope slides in balsam. 



Areas of the cephaloskeletons compared (Figure 21) were the ventral 

 surface of the basal sclerite(B.) and the oral scleri te(0. } . 



Resul ts. The basal sclerites of M. domestica and 0. aenescens are 

 shown in Figures 22 and 23 respectively. Note the presence of longi- 

 tudinal ridges(l_.R.) in the basal sclerites of both species. In Figure 

 22, the salivary duct(S.D.) can be seen where it passes into the 

 intermediate scler i te ( I . ) . 



The oral sclerites of M. domestica are shown in Figure 2k. They 

 consist of two lateral hooks(l_.H.), nearly uniform in length, joined 

 ventral ly by a median ventral arc (M.V.A. ) • Both the median ventral arc 

 and the lateral hooks are shrouded by the remains of the cuticle. Oral 

 grooves (0. G. ) leading to the oral aperature can be clearly seen. 



The orai sclerites of 0, aenescens (Figure 25) consist of two 

 lateral hooks of unequal lengths. The left hook, shown protruding above 

 the right hook, is the shorter of the two. It fits into a groove on 

 the right hook which enables both hooks to work together. Both hooks 

 are joined ventral ly by a median ventral arc. 



In addition to the oral sclerites, accessory oral sclerites are 

 present in the bucco-pharyngeal armature of 0. aenescens larvae (Figure 

 25). Beneath the lateral hooks are two oral bars(0.B.). The anterio- 



