THE BIOLOGY OF PHANETA IMBRIDANA 
(LEPIDOPTERA : TORTRICIDAE), A SEED PREDATOR 
OF XANTHIUM STRUMA RIUM (COMPOSITAE) 
By J. Daniel Hare 
Department of Ecology and Evolution* 
State University of New York 
Stony Brook, New York 11794 
Of the more than sixty North American species of Phaneta, host 
plants are known for less than one third. All of the known hosts 
are in the family Compositae, and most species feed only on the 
flowers or seeds of their host plant (Heinrich, 1923, Mackay, 1959). 
(Host plants are listed by these authors for the species of the genus, 
Thiodia, the North American members of which have been trans- 
ferred to Phaneta (Obraztsov, 1952)). Although Phaneta imbridana 
(Fernald) has been known to taxonomists for years (Fernald, 1905, 
Miller, 1970), nothing is known of its biology or life history. I 
therefore report certain aspects of the ecology of P. imbridana and 
its relationship with a local host plant, Xanthium strumarium, 
unique among the Compositae by having relatively large fruits and 
seeds. This information was obtained as part of a larger study of 
the variation in susceptibility of populations of X. strumarium to 
seed predation by more than one species of seed predator along 
Long Island beaches. 
A. Life Cycle 
Adults emerge in late August and can be found until late Sep- 
tember, with oviposition occurring throughout the adult period. 
Females oviposit directly on the surface of the full-sized but im- 
mature burrs of X. strumarium. Eggs soon hatch and the larvae 
bore through the burr wall and begin to feed on one of two seeds 
of the burr. If one seed is insufficient for complete larval develop- 
ment, larvae will attack the other seed within the same burr, or 
rarely, seeds of another burr on the same plant. Full larval devel- 
opment is completed by late September or early October, at which 
* Present address: Department of Entomology, Connecticut Agricultural Experi- 
ment Station, Box 1106, New Haven, CT 06504. 
Manuscript received by the editor October 1, 1977. 
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