Table Of ContentPROC. ENTOMOL. SOC. WASH.
102(2), 2000, pp. 350-352
AVIAN PREDATION OF THE EVERGREEN BAGWORM
(LEPIDOPTERA: PSYCHIDAE)
Robert G. Moore and Lawrence M. Hanks
Department of Entomology, 320 Morrill Hall, University of Illinois at Urbana-
Champaign, Urbana, IL 61801, U.S.A. (e-mail: [email protected])
—
Abstract. We report for the first time predation ofevergreen bagworms, Thyridopteryx
ephemeraeformis (Haworth) (Lepidoptera: Psychidae), by English Sparrows, Passer do-
mesticus (L.). Sparrows were removing bagworm bags from ajuniper planting and carried
them to sheltered locations. They fed on the larvae by squeezing their bags repeatedly
from one end to the other (to squeeze out guts and hemolymph) or by vigorously shaking
the bag to eject the larvae. Of 359 bagworm bags that had accumulated on sidewalks and
under nearby trees, birds had apparently completely extracted larvae from 62% of the
bags and killed another 36% of larvae.
Key Words: population regulation, bird behavior, predation, ornamental plants
Evergreen bagworm, Thyridopteryx Horn and Sheppard 1979, Gross and Fritz
ephemeraeformis (Haworth) (Lepidoptera: 1982, Cronin 1989). The impact of verte-
Psychidae), is an important pest of woody brate predators on bagworm populations
ornamental plants throughout the eastern rarely has been investigated; these include
United States, feeding on more than 126 rodents (Cronin 1989) and birds (English
plant species (Davis 1964, Johnson and sparrows, blackbirds, tufted titmice, chick-
Lyon 1988). The primary host plants of adees, and Carolina wrens; Haseman 1912,
bagworms are arborvitae {Thuja spp.) and Horn and Sheppard 1979, Summers-Smith
juniper {Juniperus spp.) (Johnson and Lyon 1988, Lowther and Cink 1992). In this pa-
1988), which are abundant ornamental per, we describe for the first time predation
plants (Dirr 1990). Bagworm larvae con- of evergreen bagworm by English spar-
sume the leaves and green stems of host rows. Passer domesticus (L.).
plants, and heavy infestations destroy the
Materials and Methods
esthetic value of ornamental plants, and in
extreme cases, kill them. Each bagworm In August 1998, we observed English
larva constructs a bag of silk, decorated sparrows picking bagworm larvae from a
with fragments of leaves and small branch- heavily infested juniper planting on the
es, that may reach a length of up to 5 cm campus of the University of Illinois, Ur-
in later instars (Johnson and Lyon 1988). bana-Champaign (UIUC) and carrying
Parasitoids and pathogenic fungi of ev- them away. The planting measured 550 m-
ergreen bagworm larvae may cause insuf- and was bordered on one side by a busy
ficient mortality to control populations street and on the other sides by concrete
(Balduf 1937, Kulman 1965, Barrows 1974, steps and a stone observation deck. To
Barrows and Gordh 1974, Berisford and study foraging rates and behavior, we ob-
Tsao 1975a, b, Sheppard and Stairs 1976, served sparrows for 6 days between 15 and
VOLUME 102. NUMBER 2 351
23 August 1998 for 1-2 hour periods from opening like squeezing toothpaste out a
6:30 am to 4:30 pm. During observationpe- tube, which they then consumed; 3) birds
riods, ambient temperature ranged from 14° flew away with a bag in their beaks to a
to 32° C. sheltered site where they ate bagworms (N
To determine how sparrows were feeding = 7); 4) birds shook the bag violently in
on bagworms, we placed 10 to 15 live bag- their beaks (N = 9), apparently to dislodge
worms (in their bags) on the observation the larvae so they could be consumed.
deck near thejuniper planting and recorded Consistent with the behaviors we ob-
bird behavior with a Panasonic AG-456UP served, of359 bags we collected, 62% were
video camera positioned 5-10 m away. We completely empty but otherwise intact,
videotaped birds on 18 and 19 August from 36% contained dead larvae or remnants of
11:00 am to 3:00 pm; both days were sunny larvae, and 2% had living larvae in them.
and temperatures ranged from 16° to 30° C. We conclude that larvae had been removed
We collected a total of 359 bagworm from empty bags by birds because bag-
bags from the sidewalk and beneath nearby worm larvae never voluntarily abandon
trees and shrubs (white pine, yew, and their bags. In addition, bags with dead or
birch) on 13 and 19 August; because bag- missing larvae were stained green and
worms rarely feed on these tree species brown (apparently with hemolymph), sim-
(Johnson and Lyon 1988, personal obser- ilar to the condition of bags squeezed by
vation), we concluded that birds had carried sparrows, suggesting the larvae had been
the bags there to feed. We cut these bags eaten.
open with scissors and examined their con-
tents. Many bags were partially buried, sug- Discussion
gesting that birds had been feeding on bag-
We observed bagworm predation by
worms under these trees for a long time.
sparrows at only one site; we found no ev-
Results idence of this behavior anywhere else on
At least three male and three female spar- the UIUC campus, or in nearby urban areas,
even where bagworms were abundant and
rows were preying on bagworms during our
study. They apparently located their prey English sparrows present. Apparently only
visually, possibly using the movement of one sparrow group had learned to collect
crawling larvae, either watching from rail- and feed on bagworm larvae, presumably
ings, the observation deck, or within theju- by social learning (Fryday and Greig-Smith
niper planting. Birds removed bagworms on 1994). English sparrows are opportunistic
the wing or by landing on a nearby branch. feeders, with diet composition reflecting
Rates of predation averaged 5 ± 7.8 (mean food availability and varying with locality
± SD, N = 9) bagworms taken per hour. and season (Summers-Smith 1988, Lowther
Birds carried bagworms in their beaks to and Cink 1992). Annual percent animal
nearby areas, including sidewalks, under content of their diet is typically low, but is
parked cars, and the base ofthe nearby trees often high during the summer months; an-
and shrubs where they consumed the lar- imal content is important for egg develop-
vae. ment and represents a large proportion of
Our videotape of bird behavior revealed the diet of hatchlings (Summers-Smith
the following: 1) birds often picked up bags 1988, Lowther and Cink 1992). The fairly
with their beaks (N = 43) apparently to as- high predation rates we observed suggest
sess the weight ofbags to determine wheth- that English sparrows could be important
er they contained larvae; 2) birds bit bags natural enemies in suppressing infestations
repeatedly from one end to the other (N = of the evergreen bagworm in ornamental
4) squeezing hemolymph and guts out abag plantings.
352 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
Acknowledgments formis (Lepidoptera: Psychidae). Environmental
Entomology 18: 403-407.
The authors thank John Tooker (Depart- Davis, D. R. 1964. Bagworm moths of the western
ment ofEntomology, University ofIlhnois) hemisphere. Bulletin ofthe United StatesNational
for comments on the manuscript. We also Museum 244: 1-217.
Dirr. M. A. 1990. Manual of woody landscape plants:
thank Scott Robinson (Department ofEcol- Their identification, ornamental characteristics,
ogy, Ethology, and Evolution, University of culture, propagation and uses. Stipes Publishing
Illinois) and Gil Waldbauer (Department of Company, ChampWaign, Illinois, 1007 pp.
Entomology, University ofIllinois) fortheir Fryday, L. S. and P Greig-Smith. 1994. Theeffects
advice on bagworm and bird behavior. ofsocial learning on the food choice ofthe house
sparrow (Passer domesticiis). Behaviour 128:
281-300.
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