© 2008 The Netherlands Entomological Society Entomologia Experimentalis et Applicata 130: 21–27, 2009 No claim to original US government works Journal compilation © 2008 The Netherlands Entomological Society 21 DOI: 10.1111/j.1570-7458.2008.00792.x Blackwell Publishing Ltd Fruit abscission by Physalis species as defense against frugivory Nicole D. Benda 1 *, Cavell Brownie 2 , Coby Schal 3 & Fred Gould 3 1 USDA-ARS Center for Medical, Veterinary, and Agricultural Entomology, 1600-1700 SW 23rd Drive, Gainesville, FL 32608, USA, 2 Department of Statistics, North Carolina State University, Raleigh, NC 27695, USA, and 3 Department of Entomology and W.M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA Accepted: 5 September 2008 Key words: caterpillar foraging, host plant location, Heliothis subflexa, Heliothis virescens, specialist behavior, plant architecture, Lepidoptera, Noctuidae, Solanaceae Abstract Fruit abscission as a response to herbivory is well-documented in many plant species, but its effect on further damage by mobile herbivores that survive fruit abscission is relatively unstudied. Physalis plants (Solanaceae) abscise fruit containing feeding larvae of their main frugivore, Heliothis subflexa Guenée (Lepidoptera: Noctuidae), a specialist moth. We tested the ability of H. subflexa larvae placed under the plant canopy to find and climb onto two architecturally different Physalis species. Physalis pubescens L., a low, shrub-like, spreading plant, abscises its fruit at a higher rate than Physalis angulata L., a tall arborescent plant. As a result, small larvae are more often dropped from P. pubescens. Third and fifth instars located P. pubescens faster and with a higher probability than P. angulata. Although fifth instars outperformed third-instar caterpillars at finding P. angulata, P. pubescens was located equally fast by the two instars. Heliothis subflexa located Physalis plants more successfully and more quickly than a close relative, the generalist Heliothis virescens Fabricius. The higher fruit abscission rates in P. pubescens may be an evolved response to its greater susceptibility to searching caterpillars. Introduction Many plants abscise leaves, flowers, and fruit damaged by herbivory. Because herbivore-damaged fruit may not develop properly, abscission may be an efficient way for a plant to minimize its losses by not investing further in the damaged fruit. When the herbivore is dislodged from the plant along with the abscised fruit, abscission can additionally be viewed as a direct defense against the herbivore. Many studies have documented the phenomenon of herbivores falling to the ground with the abscised plant part (Stephenson, 1981, and references within). However, the fate of these herbivores has rarely been investigated, in part because (1) relatively sessile stages of the herbivores may be involved (e.g., eggs, galls, and leaf miners) (Stiling et al., 1991; Pellmyr & Huth, 1994; Espirito-Santo & Fernandes, 2002), and (2) many herbivores can complete development within the abscised plant part (Janzen, 1971; Cross, 1973; Racette et al., 1992; Toy et al., 1992; Minchinton & Dalby-Ball, 2001) (but see investigations of a few sessile insects: Dohanian, 1944; Fernandes & Whitham, 1989; Waddell et al., 2001). Heliothis subflexa Guenée (Lepidoptera: Noctuidae) is a frugivorous specialist, feeding solely on some Physalis species (Solanaceae) (Brazzel et al., 1953; Bateman, 2006), and is the main frugivore of most natural North American populations of Physalis. Heliothis subflexa larvae feed on the berry-like Physalis fruit surrounded by a lantern-like calyx. These two parts, the calyx and the berry inside, are hereafter referred to as the Physalis fruit. Some plants in the genus Physalis drop their fruit in response to herbivory by H. subflexa. If the fruit abscises while the larva is within the calyx, the larva falls to the ground along with the fruit. Preliminary experiments have found that 14 and 22% of abscised fruits of Physalis angulata L. and Physalis pubescens L., respectively, contained larvae (JL Petzold, unpubl.). Because larvae must feed on multiple (ca. 3) fruit to complete development, most dislodged larvae on the ground must *Correspondence: Nicole D. Benda, USDA-ARS Center for Medical, Veterinary, and Agricultural Entomology, 1600-1700 SW 23rd Drive, Gainesville, FL 32608, USA. E-mail: Nicole.Benda@ars.usda.gov