conical projection, with ellipse of some 18 bulbs. 
Distribution. Florida; Argentina, Bahamas, Brazil. 
References. Spencer, 1963a: 317; Spencer and 
Stegmaier, 1973: 452; part 2, p. 245. 
Genus Hexomyza Enderlein 
Hexomyza Enderlein, 1936: 179. Type of 
genus : Melanagromyza sarothamni 
Hendel, 1923 (Europe). 
Enderlein erected the genus Hexomyz a 
for three species previously included 
in Melanagromyza , in which the costa 
ends at vein R 4+5 and which have three 
dorsocentral s . Hendel (1931-36: 570), 
followed by Frick (1952a: 376), 
synonymized Hexomyza with Melan- 
agromyza , but the genus was revived by 
Spencer (1966a) for four species 
forming twig galls, based on their 
uniform biology and the differing 
form of the male genitalia. The 
formation of a gall clearly cannot be 
considered now as of generic 
significance. One such species in the 
United States, " Agromyza " tiliae 
Couden, forming twig galls on Tilia 
americana that appear similar to those 
of the other species retained in 
Hexomyza , has now been transferred to 
Ophiomyia , in view of its clear associ- 
ation with stem-mining species (part 
2, p. 260). 
Six species are retained in Hexomyza in 
the United States, three feeding on 
Salix , one on Populus , and one intro- 
duced from Japan on Wistaria . The 
biology of another, H. toschiae , is 
unconfirmed, but the aedeagus closely 
resembles that of the Salix feeders. 
Externally these species are not sepa- 
rable from Melanagromyza , but the 
differing biology and genitalia are 
associated with differences in larval 
characters, in which the posterior 
spiracles are on short stalks (as 
opposed to the flat plate in 
Melanagromyza ) and each normally has 
three bulbs (fig. 158). The larval 
characters suggest the genus is more 
closely related to Ophiomyia than to 
Melanagromyza . 
Two of the North American species, H. 
schineri and H. simplicoides , are 
holarctic, and single species are 
known in Japan, South Africa, and New 
Zealand. In addition, H. centaureae 
Spencer (1966c) was described from 
Italy, forming stem galls on Centaurea 
solstitialis , but the generic position 
of this species may require revision 
(holotype in USNM) . 
34 
