Canadian Forest Service Publications

Physiological adaptation to temporal variation in conifer foliage by a caterpillar. 1999. Carroll, A.L. The Canadian Entomologist 131: 659-669.

Year: 1999

Issued by: Pacific Forestry Centre

Catalog ID: 5314

Language: English

Availability: Not available through the CFS (click for more information).

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Larvae of the hemlock looper, Lambdina fiscellaria fiscellaria (Guenée) (Lepidoptera: Geometridae), consume both new and old foliage within the crowns of their host, balsam fir, Abies balsamea (L.) Miller (Pinaceae), despite the poor nutritional quality generally ascribed to old tissues. Laboratory studies evaluated whether the consumption of old foliage by hemlock looper larvae could be an adaptation to the relative paucity of new versus old foliage, and the limited temporal window during which young foliage remains high in nutritional quality. Access to new foliage was critical to hemlock looper survival; 55% of larvae fed an exclusive diet of new foliage survived, whereas 5% and 0% of larvae fed exclusively 1- or 2-year-old foliage survived, respectively. Moreover, larvae reared on branches in synchrony with bud flush were more than twice as likely to survive than those whose emergence was delayed by 2 weeks. Despite the reliance by the hemlock looper upon new foliage for survival, larvae given access to both new and old foliage survived better and were heavier, than those restricted to new foliage. By incorporating older foliage into their diet, the hemlock looper can circumvent the limited availability of new foliage thereby gaining access to more abundant tissues.