Predator Presence Moves Helicoverpa armigera Larvae to Distraction

The mortality of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) neonate larvae in relation to drop‐off and soil surface temperature: the dangers of bungy jumping

“…The factors that affect drop-off rate of H. armigera neonates are less well known. While Johnson et al (2007) showed that the presence of the foliar-foraging predator Geocoris lubra Kirkaldy (Hemiptera: Geocoridae) leads to an increase in drop-off behaviour in the laboratory, the effects of temperature and the time of the day on the drop-off behaviour of H. armigera require further investigation. A drop-off rate of 15% was observed from pigeon pea plants in our field trials.…”

“…First-instar lepidopteran larvae commonly disperse from the host plant to evade predators (Cox & Potter 1986;Terry et al 1989;Johnson et al 2007); move away from an inadequate food source and high density of conspecifics (Berger 1992;Rhainds et al 2002;Kakimoto et al 2003;but see Erelli & Elkinton 2000) and due to plant effects (Ramachandran 1987;Terry et al 1989;Cottrell & Yeargan 1999). Lepidopteran larval dispersal behaviour includes dropping down on a silk thread in an action somewhat analogous to bungy jumping.…”

“…For species such as H. armigera (and larvae from: Lymantriidae, Geometridae, Tortricidae, Oecophoridae, Plutellidae, Psychidae and other Noctuidae), the objective of drop-off is not only for dispersal away from the host plant. Drop-off is also used for inter-plant dispersal and predator evasion (Awan 1985;Cox & Potter 1986;Johnson et al 2007). After dropping down, and hanging from the host plant via the silk thread, a larva may continue to drop further, especially in the case of predator evasion (Johnson et al 2007), or may lose contact with the plant due to factors such as strong winds.…”

“…Drop-off is also used for inter-plant dispersal and predator evasion (Awan 1985;Cox & Potter 1986;Johnson et al 2007). After dropping down, and hanging from the host plant via the silk thread, a larva may continue to drop further, especially in the case of predator evasion (Johnson et al 2007), or may lose contact with the plant due to factors such as strong winds. In either case the larva may find itself detached from the host plant and on the ground (Johnson & Zalucki 2005).…”

Generalist insects behave in a jasmonate-dependent manner on their host plants, leaving induced areas quickly and staying longer on distant parts

“…While there is obvious benefit to an insect in removing itself from harmful chemicals, the plant may also benefit from increased herbivore movement [17]: more dispersed feeding damage may be tolerated or compensated for more easily, and may lead to epigenetic resistance in the next generation of plants [24]. Also, there is an energetic cost to the insect that is associated with moving [25], and it may be more vulnerable to exposure [26] or predation [27]. While our understanding of insect-induced defence pathways in host plants has increased significantly in recent years [5], studies explicitly linking herbivore behaviour to jasmonate-induced changes in plant chemistry are few and all infer movement from feeding damage [19,21,23].…”