Haemolymph defence of an invasive herbivore: its breadth of effectiveness against predators

Abstract

Defensive characteristics of organisms affect the trophic linkages within food webs and influence the ability of invasive species to expand their range. Diabrotica v. virgifera is one such invasive herbivore whose predator community is restricted by a larval haemolymph defence. The effectiveness of this haemolymph defence against a range of predator functional and taxonomic guilds from the recipient biota was evaluated in a series of experiments. Eight predator species (Carabidae, Lycosidae, Formicidae) were fed D. v. virgifera 3rd instars or equivalent‐sized maggots in the laboratory, and the mean times spent eating, cleaning their mouthparts, resting and walking following attacks on each prey were compared. Prey species were restrained in five Hungarian maize fields for 1 h periods beginning at 09:00 and 22:00 hours. The proportion of each species attacked and the number and identity of predators consuming each prey item were recorded. All predators spent less time eating D. v. virgifera larvae than maggots in the laboratory, and four of the eight predator species spent more time cleaning their mouthparts. The differential responses in the predator species indicate differences in susceptibility to the D. v. virgifera haemolymph defence. The predator communities (numerically dominated by Tetramorium caespitum) in the field showed clear diel patterns in their foraging behaviour, and D. v. virgifera was consumed by fewer predators than maggots. The defence of D. v. virgifera may partly explain how invasive insects that are exposed to an extensive predator community overcome biotic resistance to the invasion process.

Tracking predation of subterranean pests: digestion of corn rootworm DNA by a generalist mite

“…However, temperature can impact DNA digestion rates (von Berg, Traugott, Symondson, and Scheu 2008), thus the ability to detect predation in field-collected soil mites is likely greater than our study indicates. Surface contamination by prey DNA needs to be considered when using PCR techniques (Remén et al 2010), especially when arthropods regurgitate gut contents (Read et al 2006) or employ reflexive bleeding as defensive strategies (Lundgren, Toepfer, Haye, and Kuhlmann 2010). …”

Predator responses to novel haemolymph defences of western corn rootworm (Diabrotica virgifera) larvae

“…These predators were chosen to expand on the range of predators evaluated by Lundgren et al (2010), and to evaluate a spectrum of hunting and feeding modes. These predators were chosen to expand on the range of predators evaluated by Lundgren et al (2010), and to evaluate a spectrum of hunting and feeding modes.…”

“…Each trial followed the protocols outlined in Lundgren et al (2010). Assays for crickets and centipedes were conducted in sterile, plastic Petri dishes (10 cm diameter, 2 cm high) under ambient laboratory conditions (30% r.h., 18°C, photocycle L16: D8).…”

“…Data collection protocols are modified from Lundgren et al (2010). In cricket trials, the cricket was introduced into a clean Petri dish and allowed to acclimate before the prey was introduced within 1 min thereafter.…”

“…larvae) display an elaborate system of chemical defences in their haemolymph, which includes a foul-tasting chemical to repel predators, and a rapid coagulation factor to ensnare a predator's mouthparts and impede its ability to feed (Wallace & Blum, 1971;Lundgren et al, 2009bLundgren et al, , 2010. The larval stages of WCR live in and feed on the roots of maize plants.…”