|scientific name Argyresthia laricella |
common name Larch Shoot Moth
This species is widely distributed in boreal habitats within the range of tamarack (larch).
In Alberta, adults fly from end of June to mid-July.
"Expanse 11-12 mm. head and palpi whitish ochreous, latter shaded with light fuscous externally on median joint; face and antennae white; thorax shining whitish ochreous; abdomen paler, legs whitish, anterior pair and tarsi of all dusted with brown. Forewing nearly immaculate, very pale shining ochreous, the inner half of costal edge and narrowly in the fold is more or less of a darker shade. Cilia whitish ochreous. Hindwing same color as cilia of forewing" (Kearfott 1908: 182). Forbes (1923: 347) notes: "R4 and R5 stalked in forewing; with fine apical striae ... second segment of palpi somewhat fuscous toward tip ... ". Freeman (1972: 696) notes: "forewing fringe pale yellowish ochreous. Hind wing and fringe grayish. Wingspread 10-12 mm". Male genitalia is discussed and illustrated in Freeman (1972: 696, fig. 24).
In Alberta this species can be distinguished from other Argyresthia by its unique forewing coloration, which is pale ochreous with a darker shade on the anterior half. Its food plant, tamarack, is not consumed by any other Argyresthia in Alberta. It might be mistaken for A. columbia which differs in size and food plant.
In mid-summer the young larva bores through the terminal twigs of larch (tamarack, Larix laricina) from tip to up to 15 cm deep, and therefore effectually killing the twigs and stopping further growth. In the fall it cuts a circular exit hole at the base where it pupates. The moth emerges in July. The dead twigs are soon broken off at the exit hole by wind.
Not of concern.
The larva feeds on tamarack, western larch, and European larch (Larix laricina) and is a twig borer but serious injury is unusual.
In Canada, it is distributed in northwestern Ontario, Nova Scotia, southeastern Manitoba, Saskatchewan, western Alberta and Southern British Columbia (Prentice 1965: 794). In Alberta it is recorded from Smith.
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