Table 2. — Plant families and genera known as hosts of Agromyzidae 
in the United States 
Total families 
(species in parentheses) 
Pteridophyta 15 (328) 
Gymnospermae 6 (115) 
Angiospermae : 
Dicotyledoneae 174 (11,551) 
Monocot yledoneae 37 (3,068) 
Hosts of Agromyzidae 
Families Genera 
51 223 
8 46 
parvicornis and Cerodontha dorsalis, 
but most plants are believed to recover 
from the initial leaf-mining damage, 
and yield is probably little 
affected. 
In Europe, damage to poplar, birch, 
and willow timber by the larval feeding 
of Phytobia species can be consider- 
able. The hosts are known of only 5 
of the 15 Phytobia species recorded in 
the United States (p. 72), and there 
appear to be no records of damage to 
commercial timber by agromyzid 
larvae. However, the nature of the 
damage to wood elsewhere is not always 
immediately apparent, and foresters 
should be aware of the potential 
damage that may be caused by agromyzid 
larvae . 
DISTRIBUTION 
Affiliations of the Agromyzidae in the 
United States are primarily with 
species in the Palaearctic Region and 
reflect the uniform fauna that existed 
between eastern Asia and North America 
across the Bering land bridge through 
much of the Tertiary period. Despite 
the water gap, which first opened up 
between eastern Asia and Alaska about 
13 million years ago, there has 
repeatedly been a land connection 
during the interglacials of the 
Pleistocene during the past 3 million 
years. This has facilitated a dis- 
persal in both directions of animals, 
plants, and of course Agromyzidae (see 
Hopkins, 1967). Many United States 
species are present also in Europe and 
even more show close relationships. 
Species with a holarctic distribution 
in Canada were analyzed by Spencer 
(1969a), and boreal species in Europe 
and North America are currently being 
reported by Griffiths (1972-80) in his 
continuing series of papers. 
Species with neotropical affinities 
are particulaly evident in southern 
Florida, and 31 species, representing 
36 percent of the total known in 
Florida, are considered to be of 
southern origin (Spencer and 
Stegmaier, 1973). Only a few species 
in southern California might fall into 
the same category (Spencer, 1981: 6). 
The fauna of other southern States is 
not well enough known to assess affili- 
ations in detail, but one new Phytobia 
species described from Arizona (part 
2, p. 271) appears to be related to 
species in Central America. 
Over 2,000 described species are known 
in the Agromyzidae, but the total must 
exceed double that number. The 
Agromyzidae are distributed throughout 
the world from the north of Greenland 
to Patagonia and the subantarctic 
islands south of New Zealand. The 
largest number of species are found in 
temperate areas of the Northern Hemi- 
sphere, where the dominant genera are 
Liriomyza and Phytomyza . However, 
many species are also in the Tropics, 
distributed from high mountainous 
areas to tropical forests at sea 
10 
