492 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
and flattened in form until just before pupation, whereas those of the 
other group become cylindrical with the head similar to the free-living 
caterpillars. The change from one type of larva to the other may 
take place in different instars in different genera and even in members 
of the same genus, and a marked change in form is always associated 
with changes in habits. In the early instars the legs and prolegs are 
sometimes absent and at most only rudimentary, whereas in later 
instars there is a considerable variation in the development of the legs. 
The full-grown larva of most species spins a silken cocoon, usually 
within the feeding mine or shelter in which it pupates. The pupae 
of all the Gracilariidae have considerable power of movement. Some 
species pass the winter as larvae, some as pupae, and others in the 
adult stage. Although most highly specialized and most numerous, 
these leaf miners seldom become pests of real economic importance. 
Their effect on the plant varies with the character of the leaf attacked, 
as well as with the extent and nature of the injury to the tissues. In 
severe infestations the mining of the foliage undoubtedly reduces the 
vitality of the host plant to a considerable extent, and the disfigure- 
ment caused by the mined, shrivelled, and tattered ‘foliage renders the 
trees or shrubs unsightly. Many species are represented in all parts 
of the United States and Canada. Their host plants include a wide 
variety of trees, shrubs, and plants. 
Some species have a single generation and others may have several 
in one year. Moths of this family may be found from early spring to 
fall. The eggs are deposited on the foliage of the food plant. In some 
species the larvae are gregarious, one mine often containing several 
larvae. Some species in the genus A/armara are miners in the bast of 
twigs of apple, balsam-fir, chestnut, oak, pine, willow, and other trees 
(Forbes, 165). 
The solitary oak leaf miner (Cameraria hamadryadella (Clem.) ) 
is one of the more common species of the Gracilariidae. It infests 
many species of oak, and the disfigured foliage caused by it often at- 
tracts attention. There may be several mines on a leaf, and each of the 
whitish blotch mines, made on the upper side of the leaf, contains only 
one larva (fig. 116). The winter is passed as a larva in the mine of the 
dried leaf. It has been reported that there may be as many as 5 or 6 
generations a year in the vicinity of Washington, DAC: 
The gregarious oak leaf miner (Cameraria cincinnatiella 
(Chamb.) ) is another common blotch miner on oaks, principally white 
oak. The larvae are gregarious, sometimes 10 or more larvae being in 
a Single mine, and in severe infestations there may be several mines to 
a leaf (fig. 117). There are two or more generations a year, and the 
winter is “passed 3 in the pupal stage. The best control measure is to 
rake up and burn the infested leaves in the winter. 
The moth of the lilac leaf miner (Gracilaria syringella (¥.)) has 
a dark-brown body, with a wing expanse of about 24 inch. The fore- 
wings are brownish, marked with six irregular transverse patches of 
yellow, and the hind wings are grayish brown. The full- grown larva 
has a brownish yellow head, the body i is pale yellowish and ‘translucent, 
and about 14 inch long. The partly grown larva in the mine is slossy, 
greenish, and spar sely clothed with long, fine hairs. This is an intro- 
duced species which is now widely distributed through many of the 
Northeastern States and parts of Canada. Its food plants on this 
continent are lilac and privet. The larvae feed gregariously between 
