2SG ^Ir. W. Wesche on si/stcmaiic aJinUics of the Plioridai 



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

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

 the fused part, but for tlie jH-esent I will accept Brues' 

 nomenclature. 



The third joint wlien 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 Coniccra aYra, Mg., P. rnjlnirni^, Mg. and indeed in every 

 species I have examined ; it appears to be a constant 

 Phorid character. 



In the Muscida} the third joint is slightly hollow at tlie 

 base, and is penetrated by a cone-siiaped 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 Pliorida; (as far as my observations go) 

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

 LoiicJioptcra fiavicauda, Mg., and in these in a modified 

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

 and D. acuticonii^i, W., and Gyninoptcruu.'^ assimilis, Stacg., 

 show it particularly well. This I consider a strong -mark 

 of afifinity, 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 J\ incrassata, 

 P. concinna, Mg., T. atcrrinia, C, atra and Gymno'phQra 

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

 and fringed with simple hairs. 



In the Muscidffi and the Hippoboscida) they arc oval 

 and have branched hairs. In the Lonchopterida; they are 

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

 Dolichopodida) they resemble the conventional tear, 

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

 In the Mycetophilida) and the Leptida^ the bordering ring 

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

 oval. In the Empida3 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 Phoridas. 



6. Tlie 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, tlie socket of which is very 



