ART. 9 FLIES OF THE GENUS STYLOGASTER ALDEICH D 



Mr. C. H. Curran, of the American Museum of Natural History, 

 who has collected more specimens of the genus than anyone else, has 

 kindly given me the following note on his observations in the Canal 

 Zone: 



During almost three months spent in the Canal Zone I observed representa- 

 tives of the genus on several occasions, usually associated with moving armies 

 of ants. However, as is only reasonable to expect, occasional specimens may be 

 found disassociated from ants, and on many occasions I captured or observed 

 them along the trails. When found singly they were hovering in small patches 

 of sunlight, and I fcund them in those locations on Barro Colorado Island, 

 Corozal, and France Field. The inference to be drawn from this is that they 

 normally occur singly and associate themselves with the ants as the army 

 travels, their numbers being augmented as the column moves along. 



There is certainly a close relationship between the flies and the ants. How- 

 ever, I failed to find any trace of oviposition on the ants, although, not having 

 read Townsend's article at that time, I arrived at the same conclusion which 

 he had reached, namely, that certain flies darting toward the ants were ovi- 

 positing. Later observations have almost convinced me that I was wrong. 

 The flies were observed to hover over any part of the moving column, and thus 

 differs d from the other flies associated with the ants. The Tachinids, Oestro- 

 gaster and AUophora, were almost invariably found near or in front of the 

 head of the column, and it is reasonably certain that they oviposited in cock- 

 roaches which were " flushed " by the ants. But Stylogaster seemed to take no 

 interest in these. In fact, they seemed intent only on hovering in patches of 

 sunlight over the army. 



I do not think that they oviposit on the ants, at least during the daytime. 

 Perhaps they do in the evening. They can not be internal parasites of the 

 army ants which I observed, because they are many times larger than th(> ants. 

 If they are parasitic on the ants, it must be as predators upon the immature 

 stages. If such is the case, the eggs might be deposited on the adult ants and 

 carried into the nests. Assuming that this is true, Townsend's conclusions and 

 my first one might have been correct. Both were made during the last hours of 

 daylight. During other observations, in the morning and early afternoon, no 

 indication of oviposition was seen. 



KEY TO SPECIES OF STYLOGASTEE 



Males 



1. Ocellar triangle long, almost or quite reaching lunule 2. 



Ocellar triangle much shorter, rarely extending a little beyond middle of 



front 5. 



2. Ocellar triangle opaque; third antennal joint four or more times the 



second on outer side (eastern United States) neglecta Williston. 



Ocellar triangle shining 3. 



3. Middle tibia with brush of long black hair on apical half of flexor side 4. 



Middle tibia plain (Panama) indistincta, new species. 



4. Middle basitarsus with a row of half a dozen erect black spinose hairs on 



a swelling on anterior side before middle ; front coxae with a tuft of hairs 



at tip which are black in front, pale behind (Brazil) ornatipes Krober. 



Middle basitarsus straight, without swelling but with a few black hairs on 

 anterior side; front coxae with only a few hairs at tip (Costa Rica). 



decorata, new species. 



