148 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 97 
in the present sample, the regular formula seems to be: acrostichals, 
1+0 (one pair of presuturals plus none of postsuturals), and dorsocen- 
trals2+1. In reality, only 10 specimens (20 percent of the sample) 
possessed this combination. The following list gives the observed 
formulae for each type of bristle, though it is obvious that there would 
be a number of different cross combinations of the acrostichal and 
dorsocentral formulae: 
Acrostichals Dorsocentrals 
1 + 0, 22 specimens 1+ 1, 6 specimens 
0 + 0, 18 specimens 2 + 1, 21 specimens 
1+ 1, 1 specimen 38 + 1, 9 specimens 
asym.® + 0, 7 specimens 2+ 2, 2 specimens 
asym.* + 1, 2 specimens 3 + 2, 2 specimens 
— asym.® 10 specimens 
50 specimens = 
50 specimens 
The actual variation was even greater than these figures indicate. 
Even where the number of bristles was the same on both right and left 
sides, those present were not always in homologous positions. What 
is recorded as one pair of presutural dorsocentrals may really be com- 
posed on the right side of a bristle in the forward position near the 
head and on the left of a bristle adjacent to the transverse suture. 
With such variation there are numerous possible combinations, and 
many of these were found in the analysis of the sample series. 
The characters that have been used in this paper for specific diag- 
nosis were found to be constant in the series or varied only within 
narrow limits. Although lack of adequate material in most of the 
other species made a similar detailed treatment impossible, observa- 
tions on the available specimens indicate that the situation in aldricha 
is probably typical for this group of flies. 
7. EUDEJEANIA ARGYROPUS (Schiner) 
Dejeania argyropus ScHINER, Reise Novara, Diptera, p. 337, 1868. 
Eudejeania pallipes var. argyropus (Schiner) Eneet, Zool. Jahrb., Abt. Syst., 
vol. 43, p. 281, 288, 1920. 
EFudejeania argyropus is one form upon which there has been general 
agreement. It is the only species I have seen with the combination of 
entirely black legs, silvery hairs covering the tibiae and tarsi, and the 
parafacials smoky golden (“goldbraun” of Schiner). 
Body color deep black; parafacials, cheeks, and occiput smoky 
golden, the occipital hairs yellow except on the lower third; palpi deep 
black; antennae entirely black; subepaulet orange-yellow; legs entirely 
3 Asymmetrical, the number of bristles not the same on left and right sides of the 
same individual. This was observed in the presutural acrostichals and in both 
presutural and postsutural dorsocentrals. 
