1921] Metcalf: Genitalia of Male Syrphide 179 
There has been great discrepancy in the numbering of these segments 
by various taxonomic and morphological students. Lundbeck (4, p. 23), 
for example, considers that the ultimate, or style-bearing segment is the 
ninth; that the postabdomen has four segments if the preabdomen has 
five and the postabdomen five when there are but four not transformed; 
although the most cephalic of the postabdomen may be hidden. Like 
all taxonomic workers, he calls the first apparent urite next the thorax 
the first abdominal segment. Berlese (/, p. 327), in his treatment of 
Eristalis tenax, interprets the numbers of the segments very differently. 
The apparent first next the thorax 1s, according to this author, in all the 
Diptera, number three; and consequently the last of the preabdomen in 
Eristalis (number four of taxonomists) he calls the sixth. His interpreta- 
tion of the postabdomen is also at variance. He considers that the style- 
bearing segment is number ten, which I think is correct.. But there are 
clearly four sclerites between this one and his so-called sixth, as shown by 
his own figure, (/, Fig. 395, p. 327). This would make the style-bearing 
segment the eleventh, or else the last of the preabdomen would be five. 
This difficulty he obviates by calling the basal two sclerites of the 
postabdomen together tergite seven, explaining that ‘“‘the seventh has 
a large basal expansion.’’ In this, I am convinced Berlese 1s in error, as 
the condition in the various genera and species clearly shows. (Follow 
Figs. M. and N. of Plate IX). The short, wide, chitinous bow (‘‘large 
basal expansion”’ of the seventh urite), sometimes retracted under 
the last sternite of the preabdomen, is a modified sternite, as shown 
by the position of the spiracles, and, if the style-bearing is in reality 
number ten, then at most only one (and not two urites, as Berlese 
claims) has been lost between the thorax and abdomen in this family. 
His “large basal expansion”’ of the seventh segment is in reality the 
sixth sternite. Lundbeck has had the truer understanding of the 
abdomen, his position being correct as to the number of segments 
present in the abdominal region (namely, nine); but probably not 
as to the correct primitive numbers of these segments. That is, he 
recognizes no lost or transformed urites at the base of the abdomen 
and consequently calls the style-bearing urite number nine instead 
of number ten. 
The evidence appears to me conclusive enough to warrant taxo- 
nomists making a change in nomenclature to conform with the morpho- 
logical evidence in this and other families. There are nine discernible 
urites cephalad of the anal segment (eleventh), the first urite apparently 
having fused with the thoracic mass. Therefore, the segment of the 
abdomen which has hitherto been called the first in all taxonomic 
writings, should be numbered two; the so-called second, three; three, 
four, etc. While this will seem radical to systematists, it is clear that a 
nomenclature founded on error cannot permanently endure and if the 
change must come, the sooner and more generally it is adopted the 
more rapid and stable our progress will be. In this paper, therefore, the 
writer has adopted this nomenclature for the abdominal segments. 
