Adults appear in late July and lay their eggs on the leaves of their hosts. At first 
the larvae feed within mines in the leaves. Then they emerge and construct tiny 
cases in which they migrate to the twigs where they spend the winter. Feeding is 
resumed in the spring with each larva eating out a tiny circular hole in a leaf and 
then, without leaving its case, mining out an area between the larger veins as far as 
it can reach. The case is enlarged as needed to accommodate the growing larva, 
eventually reaching a length of 9 to 10 mm. This species 1s primarily a pest of shade 
and ornamental trees. The mined parts of leaves turn brown and, when numerous, 
are unattractive. Fortunately, outbreaks are usually limited. 
The larch casebearer, C. Jaricella (Hubner), an introduced species, was first 
recorded in North America in Massachusetts in 1886. It now occurs throughout 
most of the range of tamarack in North America, west to central Minnesota and 
northwestern Ontario. In 1957, an infestation was also discovered on western larch 
in Idaho (298). It is now widespread in the region of western larch. The adult is 
silvery to grayish brown, has narrow wings fringed with long hairlike scales, and a 
wingspread of about 9 mm. Full-grown larvae are about 6 mm long. The pupa is 
brown. This species is one of the most serious defoliators of larch in North 
America. Outbreaks have been occurring at about 8-year intervals in eastern Can-_ 
ada. Heaviest losses result from reduced growth, twig mortality, and increasing 
numbers of adventitious shoots. Trees completely defoliated for 2 or more con- 
secutive years may be killed. 
Eggs are deposited singly on needles in early summer and hatch in about 2 
weeks. The newly hatched larva bores directly into a needle and continues to mine it 
until late summer. Then the larva lines a hollowed section of the needle with silk 
and chews the section free at both ends thereby forming a case. The remaining . 
larval period is spent in the case, which is enlarged as needed. A single larva may 
mine several needles before the needles fall. Before the onset of cold winter 
weather, the larva migrates to an outer twig or branch to which it fastens its case, 
usually at the base of a bud. Several cases may be found grouped together around 
the bases of spurs from which new needles arise in the spring. The most serious 
damage is done by the large larvae as they feed on newly developing foliage during 
the spring. Adults emerge from late May to early July, depending on locality and 
season. There is one generation per year. 
The larch casebearer is attacked by more than 50 species of native parasites in 
eastern America, but none is particularly effective in control. Two introduced 
hymenopterous parasites, Agathis pumila (Ratzeburg) and Chrysocharis 
laricinellae (Ratzeburg) are now widely distributed and are believed to be quite 
helpful in control. Rearing methods have been devised for these parasites (/046). 
The birch casebearer, Coleophora serratella (L.), an introduced species first 
observed in North America in Maine in 1927, is now known to occur throughout the 
Northeastern States and from Newfoundland and New Brunswick to southern 
Ontario. In the past, this insect was also called the cigar casebearer. Its favored 
hosts are paper, gray, and European white birches. Eggs are laid in July along the 
midribs and larger veins on the undersides of leaves. Young larvae enter the leaves 
and feed as miners for several days, then they emerge and construct cases in which 
they live and feed thereafter. Winter is spent in cases firmly attached to the bark, 
usually in crotches of limbs. In the spring, the larvae feed on buds and young 
leaves, mining as far as possible without leaving their cases. Infested leaves tend to 
shrivel. This species has been abundant in Quebec, New Brunswick, and northern 
Maine. Many stands of paper birch in New Brunswick were completely defoliated 
134 
