shown by the male genitalia to belong 
correctly in Japanagromyza . This 
species has 3+1 dorsocentral bristles 
(dc) and is the first in the genus to 
be known with a strong presutural dc. 
The color and head shape also differ 
from the form previously known in the 
genus . 
In Melanagromyza , the normal arrange- 
ment of dorsocentral bristles is two 
in the postsutural area (rarely 
three); two species, M. quadrisetosa 
and M. trispinella , were recorded in 
California with a strong presutural dc 
bristle. They are the only species in 
the world in this genus known to 
possess this bristle. 
Many groups of closely related species 
in the genera Melanagromyza , Ophiomyia , 
Cerodontha ( Dizygomyza ) , Liriomyza , 
Calycomyza , and Phytomyza are known 
that cannot be reliably separated on 
external characters, and identification 
is only possible from examination of 
the male genitalia. It is apparent 
that in several instances even the 
genus cannot be accurately established 
on external characters alone. 
There can be difficulty in deciding 
between Agromyza and Phytobia owing to 
the course of the subcosta in the 
latter genus approaching that normal 
in the Agromyzinae. However, the 
stridulating mechanism in both sexes 
of Agromyza (figs. 346-348) provides a 
certain means of identifying 
the genus . 
Hendel (1920: 114; 1931: 16) differ- 
entiated Ophiomyia and Melanagromyza 
by the presence in the former of a 
raised facial keel dividing the 
antennae and, in the male, the 
presence of a vibrissal fasciculus 
(figs. 221, 304) replacing the simple 
vibrissa in Melanagromyza . In the 
1960's, these external characters were 
found to be inadequate for differenti- 
ating these two genera. The male 
genitalia and larval morphology and 
biology clearly showed that several 
species, although appearing like 
typical Melanagromyza , correctly 
belonged in Ophiomyia (see Ophiomyia 
key, p. 39). ~ ~ — — 
Some species in Liriomyza and 
Phytoliriomyza can appear virtually 
identical in external characters. The 
only certain way of assigning them to 
the correct genus may be the presence 
or absence of the stridulating 
mechanism in males of Liriomyza 
(figs. 621, 622). As an example, L. 
marginalis and I>. melampyga may be 
cited. Each is largely yellow, with a 
black or gray banded mesonotum, and 
the central area adjoining the 
scutellum is yellow (fig. 673). The 
male genitalia, however, will frequent- 
ly indicate the correct genus. 
With adults of some species of 
Phytomyza and Chroma tomyi a that are 
indistinguishable in external 
characters, examination of the male 
genitalia is necessary to identify the 
genus. However, in a few instances, 
the genus is not immediately apparent 
even from the genitalia. One such 
species is P. clematoides , in which 
the divided and dorsally directed 
distiphallus (fig. 1217) might be 
mistaken for the "supporting sclerites" 
present in all species of Chroma tomyia 
(figs. 1275, 1290). In this species , 
the correct generic position was 
finally confirmed by examining the 
puparia. 
However, the type of aedeagus of the 
feeders on Caprifoliaceae (figs. 1285, 
1295) and on Poaceae (figs. 1258, 
1261) is distinctive and readily recog- 
nizable. Unfortunately with our 
present knowledge it will not be 
possible in some instances to identify 
females in these two genera even to 
genus. Therefore, Phytomyza and 
Chromatomyia species, for convenience, 
have been included in a single key 
(p. 175). 
14 
