lunule often silvery. The venation is 
variable, with the costa ending at 
R 4+5 or extending to M 1+2, and the 
outer crossvein is present or 
lacking. The subcosta normally runs 
parallel to vein R 1 directly to the 
costa (fig. 5), but in some species 
appears to join R 1, as in Agromyza 
(fig. 4). Such specimens can be 
misidentif ied as Agromyza species, and 
Sasakawa (1963a) even erected the 
genus Shizukoa owing to the difficulty 
of detecting the correct generic 
position in such instances. 
When Tschirnhaus (1971) discovered the 
stridulating mechanism in both sexes 
in Agromyza (p. 57), he also 
established that this is lacking in 
Phytobia , and this provides a reliable 
means of separating the genera when in 
doubt . 
Phytobia in its present concept is 
restricted to the species whose larvae 
bore in the cambium of twigs or trunks 
of trees. Of the 15 species known in 
the United States, the hosts of only 5 
have been established: Acer , Amelan- 
chier , Be tula , Crataegus , and Prunus. 
Greene (1914, 1917) discussed the 
biology in some detail of three 
species and also recorded finding 
larvae in Ilex monticola and Quercus 
rubra . It is virtually certain that 
Populus and Salix are additional hosts 
of American species. P. f lavohumeralis 
was described from an area in Alberta, 
where the dominant tree was Populus 
balsamifera , which was probably the 
host. A single specimen caught on 
Salix in New York is included in the 
key here, but it is not formally de- 
scribed pending discovery of sufficient 
material for accurate diagnosis. 
A detailed account of larval feeding 
in Prunus was given by Grossenbacher 
(1915), and he also discussed his 
rearing technique. Other hosts are 
known in Europe, with species recorded 
from Alnus , MaJLus, Populus , Salix , and 
Sorbus, and in Canada a specimen has 
also been reared from Fraxinus . 
Larval feeding damages wood subsequent- 
ly used commercially, causing so-called 
"pith flecks." These were illustrated 
by Spencer (1973a: pi. 9) when discuss- 
ing the economic importance of the 
genus . 
Phytobia is widely distributed in all 
faunal regions, with a total of 50 
species. Striking species with 
pictured wings are known in Brazil 
(Spencer, 1966e), and a key to 11 
species in the Neotropical Region was 
given by Spencer and Stegmaier (1973: 
174). Eight species have been 
recorded in Europe (Spencer, 1976a: 
147), eight in the Papuan subregion 
(Sasakawa, 1963b, as Shizukoa ) , and 
nine in Australia (Spencer, 1977d: 
122). Remarkably, four species are 
present on Lord Howe Island, but the 
genus appears not to have reached New 
Zealand . 
Phytobia is generally accepted as one 
of the most primitive genera in the 
family. Suss and Miiller-Stoll (1975) 
described Palaeophytobia platani from 
larval feeding tracks in wood 
identified as Platanoxylon sp. in 
Hungary from Upper Miocene, but no 
modern species is known in Platanus . 
Siiss (1979) also described a new 
species, Protophytobia cupressorum , 
from the Netherlands from feeding 
tracks in wood of Tertiary age 
considered to belong to the 
Cupressaceae , identified as 
Juniperoxylon silesiacum (Prill) 
Krausel. Similar feeding tracks are 
recorded from modern Callitris 
(Cupressaceae) in Australia, and 
references are given to the possible 
feeding of Phytobia spp. in Abies , 
Cunninghamia , Cupressus , Juniperus , 
Picea, and Pinus . It must, however, 
be emphasized that there may be 
difficulty in establishing even the 
order of insect producing feeding 
tracks in wood, particularly when a 
fossil. An insect identified as a 
Phytobia sp. has been found feeding in 
Nothofagus in Chile, but it was 
subsequently established that the 
species was a microlepidopteron in the 
family Opostegidae. It is therefore 
to be hoped that every effort will be 
72 
