286 Mr. W, Wesche on systematic affinities of the Plioridsi 



joint is a fusion of the first and second. Personally I am 

 inclined to go further, and see more than two joints in 

 the fused part, but for the present I will accept Brues' 

 nomenclature. 



The third joint when seen in microscopic section is 

 found to be hollow, very neatly fitting round a bulb at the 

 end of the second joint, which is articulated by a short 

 process descending from the third joint. This is well seen 

 in Conicera atra, Mg., P. rujicornis, Mg. and indeed in every 

 species I have examined ; it appears to be a constant 

 Phorid character. 



In the Muscidse the third joint is slightly hollow at the 

 base, and is penetrated by a cone-shaped process from the 

 second joint which is in contact on all sides, there being- 

 no special articulating part. A similar arrangement to 

 that found in the Phorida3 (as far as my observations go) 

 is only found in a few genera in the Dolichopodidse and in 

 LonclwptercL Jiavicauda, Mg., and in these in a modified 

 form. It will be found in most of the genus Doliclwims, 

 and D. acuticornis, W., and Gymnopternus assimilis, Staeg., 

 show it particularly well. This I consider a strong mark 

 of affinity, which as I shall show later is only one among 

 many. 



5. The thoracic spiracles. The anterior thoracic spiracles 

 are very constant in character in families, and show little 

 or no variation in genera and species. In F. incrassata, 

 P. concioma, Mg., T. atcrrima, G., atra and Gymnophora 

 arcuata, Mg., they are circular, with chitinous rings or edges, 

 and fringed with simple hairs. 



In the MuscidjE and the Hippoboscidse they are oval 

 and have branched hairs. In the Lonchopteridse they are 

 oval, but more rounded than in the Muscidae. In the 

 Dolichopodidge they resemble the conventional tear, 

 rounded at one end, and gradually tapering to a point. 

 In the Mycetophilidse and tlie Leptidae, the bordering ring 

 is not so well defined and the shape is inclined to the 

 oval. In the Empidne they are circular, and as in the last 

 four families, simply ciliated, and are very similar to the 

 organs as they are found in the Phoridse. 



6. The structure of the compound eyes. In the Nematocera 

 the compound eyes often consist of a chitinous plate, 

 pierced with circular apertures for the lenses. When the 

 eyes are pubescent, the sub-quadrate space between four 

 lenses is occupied by a hair, the socket of which is very 



