Jrom the Rio Nautla, State of Vera Cruz. 273 
find to vary greatly, being nearly or quite obsolete in some 
males. ‘The supposed characteristic black on tip of the 
female abdomen is often subobsolete or wholly wanting. 
Size is another character that cannot be relied upon in 
this group, which seems to approach the nearly allied family 
Conopide in this respect. In some species of Zodion, for 
example, the disparity in size is sometimes very great. I 
have two specimens of the same sex (male) of Z. splendens, 
one of which is at least five times as large, bulk for bulk, as 
the other, and yet does not differ appreciably otherwise (see 
forthcoming papers on Diptera of the Organ Mountains and 
Diptera of the Mesilla Valley, N.M.). 
The scutellum is often subtranslucent, more or less pol- 
linose, so as to appear nearly concolorous with the yellow or 
reddish abdomen in species with such colours prevailing, 
rather than with the thorax. This character cannot be 
trusted, as it is changeable in the same specimen, according 
to age, degree of preservation, &c. Moreover, there are all 
gradations in specimens in this respect, so that no separation 
can be made. 
The form of the abdomen is not always constant as a 
sexual character. Females of the smaller forms often ap- 
proach the male in the wider subflattened abdomen, while 
some males even boast the subcylindric abdomen of the 
female. In all cases of doubt as to sex, the only criterion to 
be depended upon lies in the sexual organs themselves. 
The forms of Trichopoda exhibit such a range in size, 
coloration of wings, abdomen, &c., that it is likely that many 
of the older names will have to be classed as synonyms, or 
continued only to mark varieties. The above remarks on 
colour variation apply more particularly to the smaller forms, 
pennipes and var, pilipes. 
The following table of species and varieties of Trichopoda 
includes only the forms, and sexes of those forms, known to 
me from examination :— 
Table of Species of 'Trichopoda. 
Males. 
1. Wings with only a narrow internal border, 
ny aline) cae eta a pore tcr eet. : 5. 
Wings with at most the costal half coloured, 
the inner half or more clear............ 2. 
2. Abdomen black, with a large pale yellow 
spot on each side at base .............. phasiana, sp. n. 
Abdomen brown or black, without such 
spots, golden pollinose on apical s segments. 3, 
