BIOLOGY 
Life History 
All Agromyzidae are feeders on plant 
tissue. The white or yellowish oval 
egg is laid beneath the epidermis at 
the appropriate oviposition site, 
which may be at the leaf margin, at 
the leaf tip, indiscriminately anywhere 
in the leaf blade, or occasionally in 
the stalk, as in Phytomyza ilicis . 
Normally the larva emerges within 
a few days and feeds to form a channel 
or mine within the plant, which often 
will be characteristic of the 
particular species. Stem-boring 
species may oviposit in the leaf. The 
larva quickly feeds toward a vein and 
then works downward through the 
petiole to the stem. Some species may 
oviposit directly in the stem. The 
larval feeding can continue from about 
1 week to several months, depending 
partly on the temperature, and is 
essentially a fundamental aspect of 
the life cycle. Species with 
several generations in quick 
succession, as in Liriomyza sativae , 
will feed rapidly, whereas those with 
only a single generation per year 
normally feed more slowly and sometimes 
intermittently throughout the cold 
winter months. 
Pupation normally occurs on the 
ground. The larva either drops from 
the plant and transforms after some 
hours or transforms immediately on 
leaving the leaf and falls to the 
ground as a puparium. A few leaf 
miners pupate within the leaf at the 
end of the mine, particularly in the 
genus Chromatomyia . Most seed feeders 
and stem borers pupate within the plant 
at the feeding site. The pupal period 
varies greatly with the species, but 
it is most frequently about 2 weeks, 
although it may be as long as 6-10 
months . 
The Agromyzidae are well known as leaf 
miners. However, all parts of the 
plant are attacked, including stems, 
seeds, and more rarely roots, and in 
the case of trees, young twigs or the 
outer layer of the trunk. 
Leaf Mines 
The characteristic form of these mines 
or feeding tracks is a substantial aid 
in identifying Agromyzidae. Although 
individual mines may vary considerably, 
the essential pattern remains constant 
for each species. The main types of 
mines are linear or serpentine (figs. 
649, 776), blotchlike, approximately 
circular or elongate (figs. 903, 908), 
or more irregular, with short 
offshoots (fig. 935). In many 
instances, the larva forms a short 
linear mine in the first instar, and 
after the first molt the feeding 
instinct changes and the larva then 
forms a blotch mine (fig. 359). This 
may completely envelop the earlier 
linear section, which will nevertheless 
remain detectable from the frass 
arrangement . 
The part of the leaf that is mined is 
frequently characteristic. Most mines 
are formed on the upper leaf surface, 
in the area of the palisade parenchyma • 
More rarely, very shallow mines are 
made immediately beneath the epidermis 
of the leaf, as in Liriomyza schmidt i , 
or in a few species the larva feeds 
exclusively on the lower leaf surface, 
in the spongy parenchyma, as in 
Chromatomyia lactuca . Some mines are 
invariably associated with the margin 
of the leaf, others occur exclusively 
along the midrib or possibly one of 
the stronger lateral veins; this is 
the normal form in the pest species 
Liriomyza huidobrensis (fig. 713). 
The arrangement of frass in the mine 
is frequently characteristic. It may 
be deposited in single, widely spaced 
pellets, or it may be in rather contin- 
uous strips, or all frass may be 
excreted immediately prior to pupation 
at the end of the mine, to which the 
puparium is sometimes firmly glued, as 
in Calycomyza humeralis or C. promissa 
(fig. 883). 
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