CALLIPHORA ERYTHROVEPHALA, MG. 291 



parallel lines leading to like results. One of our British blood- 

 suckers, Haematobia stimulans, Mg., seems to have halted in a 

 stage of development, as tracheae can be found (it is true, in a 

 very degenerate state) at the end of the proboscis, which in all 

 other respects is similar to that of H. irritans, L. All the flower- 

 feeders show the taste-hair at the end of each trachea, exactly 

 as it is found in the Blow-fly ; and, as it is present in a similar 

 situation on the labella in Tipula and Pty diopter a, it is obviously 

 a very archaic organism. 



There is yet another point which throws light on the evolution 

 of the Blow-fly and these kindred specialisations, and that is the 

 remnants of the maxillary palpi, those curious hairy processes 

 which are attached to the stipites. They are very evident in 

 a number of flies in the Anthomyia group of the Muscidae, where 

 the fourth vein is straight, and are still obvious in genera of the 

 Muscidae proper, where the vein begins to curve ; but, as would 

 be expected, they disappear directly the mouth is specialised, as in 

 Drymia and Stomoxys, though Drymia has the straight and 

 Stomoxys the curved vein. Where, however, the mouth is un- 

 specialised as in the House-fly | Musca domestica), but the fourth 

 vein is still more curved than in Stomoxys, the remnants are 

 much less, but still persist, whilst in the Blow-fly they have 

 disappeared altogether ; so 1 am able to say with tolerable 

 confidence that the mouth shows us that, although it is not one of 

 the latest, it is one of the later types in the Muscidae. 



Summary. — (1) That specialised types of the proboscis in the 

 Muscidae do not show that the genera are more n< arly related 

 than is indicated by their inclusion in the family, but have arisen 

 on lines of parallel development. 



(2) That probably these genera branched off from the normal 

 type in the following order, the oldest being placed first : Drymia, 

 Stomoxys, Eaemotobia, Siphona, Prosena, and Glossina. 



(3) That the Blow-fly (Calliphora) is one of the later, though 

 not specialised genera in the Muscidae. 



