Host Selection 
Most Agromyzidae are monophagous, that 
is, limited in their choice of host to 
a single plant or more often several 
species within the same genus, or they 
are oligophagous , feeding on several 
genera within a single family or on 
several related families of the same 
order. Very few species are truly 
polyphagous, feeding on a wide range 
of unrelated hosts. Common polyphagous 
species in the United States are 
Liriomyza huidobrensis , L. sativae , 
and L. trifolii. 
HOST PLANTS 
Agromyzidae feed on a wide range of 
hosts, including ferns and both main 
groups of angiosperms, the Dicotyle- 
doneae and Monocotyledoneae . Until 
recently there has been no evidence to 
suggest that any species might feed on 
conifers. However, Siiss (1979) has 
identified feeding tracks in Tertiary 
fossil wood of Juniperoxylon silesiacum 
(Prill) Krausel from the Netherlands as 
belonging to an agromyzid ancestral to 
the modern genus Phytobia , which he has 
named Protophytobia cupressorum . He 
also considered feeding tracks in 
modern Callitris drummondii Benth. & 
Hook. (Cupressaceae) from Western 
Australia as belonging to a Phytobia 
species. If these findings can be 
substantiated, they will represent a 
remarkable discovery and the possibili- 
ty that Phytobia species are present 
in Coniferae in the United States and 
cannot be entirely excluded, although 
it is improbable. 
Of the 531 species of Agromyzidae 
recognized in the United States, the 
host is known for 250, or slightly 
less than 50 percent. The plant 
species in the United States exceed 
15,000, many of which will serve as 
hosts for the Agromyzidae, either of 
species already known or of those to 
be discovered. The scope for further 
collecting is thus enormous. Table 2 
shows the total number of plant 
families and species (Shetler and 
Skog, 1978) and the number of families 
and genera known as agromyzid hosts. A 
complete host list is given on page 224. 
ECONOMIC IMPORTANCE 
The economic importance of the Agro- 
myzidae was discussed in detail by 
Spencer (1973a). Over 150 species of 
cultivated plants throughout the world 
are attacked by a similar number of 
agromyzid species. Such pest species 
occur on a wide variety of crops, but 
the most serious damage is caused by 
leaf miners in the genus Liriomyza in 
warm temperate areas in North and 
South America and by the stem feeder 
Ophiomyia phaseoli (Tryon) on beans in 
the Old World tropics. This species 
has recently reached Hawaii. In 
temperate areas of Europe and North 
America, many species whose regular 
hosts include several crop plants occur 
only periodically in sufficiently 
large numbers to cause significant 
damage . 
In the United States, Liriomyza 
sativae , L. trifolii , and L. ~ 
huidobrensis are the most serious 
pests. L. sativae is highly 
polyphagous, attacking many truck 
crops, and occurs widely through- 
out the Southern States from Florida 
to California. L. trifolii is a 
regular pest in Florida, particularly 
on celery and chrysanthemum, and 
appears to have been introduced to 
California from Florida, where it is a 
constant problem in chrysanthemum 
nurseries. L. huidobrensis is not 
known in the East, but it is common in 
southern California and also in South 
America, attacking many cultivated 
plants, including ornamentals. 
Chroma tomyia syngenesiae regularly 
builds up large populations in 
California (Frick, 1972) and can be a 
serious problem on lettuce. Cucurbits 
and leguminous crops, including peas 
and alfalfa, can be seriously damaged 
by the three Liriomyza species. Also, 
L. trifoliearum and Agromyza frontella 
can occur in pest populations on alfal- 
fa. All cereals may be attacked by A. 
9 
