E. T. CRESSON, JR. 69 



brown and the wings peculiarly marked as is shown in figure 8. 

 Care, however, should be taken not to confuse it with species of 

 Hoplodictya. 



Geyiotype. — Musca umbranim Linne (1758). [Alonotypic] 

 Eyes vertically oval. Frons attaining bases of antennae; lunule 

 not prominent, with one orbital bristle; mesofrontalia linear, 

 sometimes scarcely discernible; lunule not prominent. Second 

 antennal joint quadrate; third, broad as long, triangular, truncate 

 apically; arista sparsely black plumose. Sternopleura setulose. 

 Wings spotted with white and brown; thirfl and fourth veins 

 parallel. 



The name Monochaefophom was proposed for a genus having 

 Musca unibrarum Linne as its type species, and, as a genus, 

 replaces Dictya Meigen (1803) of some authors. The latter 

 genus, as considered by recent authors, is erroneously based on 

 Musca iimbrarum Linne (1758), instead oi M .umhrarum Fabricius, 

 the latter, not the former, being one of the originally included 

 species. In Meigen's original diagnosis of Dictya, two species 

 are cited thus: ^^ Musca cucukma, unibrarum Fabr." These two 

 were there credited to Fabricius, although the names were first 

 used by Linne and so credited by Faljricius; but Meigen, follow- 

 ing the custom of the early authors, referred to Fabricius even 

 for Linne's species. In this case, however, Fabricius, apparently, 

 did not know or misidentified Linne's species. There is nothing 

 in the original diagnoses of M. umbrarum Linne or of M. um- 

 braruui Fabricius, to guide one in assuming that Meigen had either 

 of these species before him at the time he proposed Dictya. That 

 the above names apply to distinct species may be satisfactorily 

 demonstrated, by comparing Musca (Monochaetophora) umbrarum 

 Linne and Musca (Platystoma) umbrarum Fabricius with the two 

 original diagnoses. The snow white face (fronte) in the former, 

 and the grayish, brown banded, abdomen in the latter, may be 

 considered sufficient characters of distinction. It may thus be 

 assumed, and it is generally recognized, that Fabricius was in 

 error in his determination of Linne's species. Now upon com- 

 paring specimens of the two species above noted, with Meigen's 

 diagnosis of Dictya, we find that it calls for porrect antennae, of 

 three joints; the first small; second flat, elongate; third flat with 

 superior margin excavated, with basal, plumose arista; frons 



TRANS. AM. ENT. SOC, XLVI. 



