396 



W. H. HARRIS ON THE DENTITION OF THE DIPTERA. 



of Beelzebub. Each lobe contains five rather short, stout, 

 bidentate teeth, which on their conical portions are beset with 

 very fine serrations. Diagram (No. 5). All traces of pseudo- 

 tracheae have disappeared ; their positions, however, are occupied 

 by long, lance-like organs. Behind each tooth are curiously- 

 paired organs, the use of which is problematical. 



The foregoing examples have been selected, not without due 

 consideration, as illustrating the chief point it has been the 

 object of my paper to refer to. An examination of the objects 

 in my cabinet would disclose many connecting links, but as ail 

 the species have not been identified I have refrained from 

 introducing them. 



To briefly recapitulate, I have attempted to show that the 

 dental organs of Diptera may be divided into two groups, the 



2 i. 



Lateral aspect of teeth of : — 



1. Hydrotaea irritaiis. > 



2. Scato2)haga stercoraria. 



3. Sckaenomyza litorella. 



4. Caenosia sexnotata. 



5. Stomoxys calcitrans. 



compound and the simple. The former contain from two to 

 four rows of teeth, developed on different lines ; the simple 

 contain organs more highly difterentiated, and approaching in 

 form the lower orders of vertebrate types. With the develop- 

 ment of the teeth there has throughout been a gradual 

 diminution of pseudo-tracheae, both in size and number, until 

 they disappear entirely. 



It may be asked whether extended investigations would be 

 merely an interesting occupation — an amusement for an idle 

 curiosity — or whether any scientific value could be derived from 

 them. I fear I am unable at present to ofter a definite opinion 

 that would be quite satisfactory. I may, however, say that, so 



