Temperature influence on the reproduction of Podisus nigrispinus, a predator of the noctuid larva Alabama argillacea

The influence of temperature on thereproduction and longevity of Podisusnigrispinus (Dallas) (Heteroptera:Pentatomidae) fed with Alabamaargillacea (Hübner) (Lepidoptera:Noctuidae) larvae was studied. This predatorwas reared at constant temperatures of 20, 23,25, 28, 30 and 33 ± 0.2 °C, all atrelative humidity of 60 ± 10%, and aphotoperiod of L:D 14:10. Fecundity of P.nigrispinus at the various temperatures rangedfrom 401.2 (33 °C) to 841.3 (28 °C) eggs/female. The preoviposition,oviposition peak, and declining ovipositionperiods of P. nigrispinus were affectedby temperature [preoviposition period: 4.0 (33 °C) to 13.2 (20 °C) days;duration of oviposition peak period: 9.0 (33 °C) to 33.0 (20 °C) days; andduration of declining oviposition period: 16.0(33 °C) to 46.0 (20 °C) days].Longevity of females and males of P.nigrispinus ranged from 28.4 (33 °C) to88.6 (20 °C) days, and from 42.7 (33 °C); to 114.3 (20 °C) days,respectively. These data are useful in relationto the development of population dynamicsmodels to underpin programmes of biologicalcontrol.     

Relationship between predation by Podisus nigrispinus and developmental phase and density of its prey,Plutella xylostella

This study evaluated the predation by Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) at various densities of larvae and pupae of the pest Plutella xylostella (L.) (Lepidoptera: Plutellidae). We tested predator behavior of female P. nigrispinus at six experimental densities (1, 5, 10, 15, 20, or 25 prey items in a 1‐l transparent plastic container, replicated 15 times for each density) of both the fourth instar and pupae of P. xylostella. The number of prey consumed was monitored every 15 min for 12 h and was subsequently monitored at 24 h. Podisus nigrispinus females were weighed before and after the experiments to determine the effect of different densities of prey on their weight gain. Female predators had a Type‐II functional response, with attack rate estimated at 1.387 and 0.260 and a handling time of 0.091 and 0.183 h^?1 for larvae and pupae, respectively. Podisus nigrispinus consumed on average 10.9 larvae or 5.5 pupae in 24 h. Despite the similarity of the response type, P. nigrispinus preferred to feed on larvae, rather than on pupae.     

Host plant and the predator Podisus nigrispinus: when the defense compounds of the plant affect the third trophic level

Many herbivorous insects can overcome chemical plant defenses, using the plant's defensive products for their own good, as a defense against predators. Eucalyptus spp. (Myrtaceae), recently introduced in Brazil, are rich in secondary compounds; however, there are reports that these plants have been suffering from population outbreaks of defoliating Lepidoptera in Brazil. The predator Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) has been used against herbivorous insects in eucalyptus plantations, but little is known about its establishment in the field. This study aims to investigate whether the effectiveness of this predator may be affected indirectly by compounds of eucalyptus plants, when compared to guava, Psidium guajava L., a Brazilian native species of Myrtaceae. Thus, we evaluated the performance of P. nigrispinus on larvae of Thyrinteina arnobia (Stoll) (Lepidoptera: Geometridae) reared on eucalyptus (exotic species) or guava plants (native species). Podisus nigrispinus performance (reproduction and survival) was better on larvae fed on guava than on larvae fed on eucalyptus. It is possible that the negative effect on the predator's development occurred because of the plants’ secondary compounds appropriated by caterpillars, due to the short coevolutionary history between eucalyptus and the predator. The data suggest that the chemical compounds that could help the plant's defenses against herbivores may also affect their natural enemies, especially when the interaction between plant and natural enemy involves an exotic plant recently introduced into the insect's habitat.     

Consumptive and non‐consumptive effects of wolf spiders on cotton bollworms

Larvae of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) that survive on genetically modified Bt cotton (Gossypium hirsutum L., Malvaceae) contribute to the risk of widespread resistance to Bt toxins. Current resistance management techniques include pupae busting, which involves deep tilling of the soil to kill overwintering pupae. Unfortunately, pupae busting runs counter to soil and water conserving techniques, such as minimum tillage. This problem could be relieved with biological control methods, whereby predators attack either larvae going to ground to pupate or moths emerging from the ground. We found that the wolf spider Tasmanicosa leuckartii (Thorell) (Araneae: Lycosidae), a common inhabitant of Australian cotton agroecosystems, is an effective predator of H. armigera, attacking and killing most larvae (66%) and emerging moths (77%) in simple laboratory arenas. Tasmanicosa leuckartii also reduced the number of emerging moths by 66% on average in more structurally complex glasshouse arenas. Males, females, and late‐instar juveniles of T. leuckartii were similarly effective. Tasmanicosa leuckartii also imposed non‐consumptive effects on H. armigera, as when a spider was present larvae in the laboratory areas spent less time on the cotton boll and more time on the soil and more mass was lost from the cotton boll. Increased loss of boll mass likely reflects changes in H. armigera foraging behavior induced by the presence of spiders (indirect non‐consumptive effects). Helicoverpa armigera spent more time as pupae when the spider was present in simple laboratory arenas, but not in more complex glasshouse enclosures. Overall, results indicate that T. leuckartii spiders can be effective predators of H. armigera late instars and moths but also suggest that, under some conditions, the presence of spiders could increase the damage to individual cotton bolls.     

Impact of plant architecture and extraguild prey density on intraguild predation in an agroecosystem

Several models and experimental studies conducted in confined environments have shown that intraguild predation (IGP) can modulate population abundances and structure communities. A number of ecological and abiotic factors determine the nature and frequency of IGP. This study examined the effect of plant architecture and extraguild prey density, and their interactions, on the occurrence of IGP between two species of ladybird, Harmonia axyridis (Pallas) and Propylea quatuordecimpunctata L. (both Coleoptera: Coccinellidae). Theoretical concepts predict that IGP levels would increase with a decrease of both extraguild prey density and plant structural complexity. We conducted a factorial experiment in an open soybean field into which coccinellid larvae were introduced in experimental plots for a period of 5 days. We tested two levels of soybean aphid [Aphis glycines Matsumara (Hemiptera: Aphididae)] density, low and high (100 and 1 000 aphids per plot, respectively), and two levels of plant complexity, low (by removing half of the branches from the soybean plants) and high (by leaving plants intact). We used species‐specific molecular markers to detect the presence of P. quatuordecimpunctata in the digestive tract of H. axyridis. Molecular gut‐content analysis of H. axyridis revealed that rates of IGP were higher (20%) at low aphid density than at high aphid density (<6%). Decreased plant complexity did not impact the frequency of IGP. In accordance with existing literature, this study demonstrates that IGP is amplified at low extraguild prey density. We conclude that considering environmental factors, such as extraguild prey density, is crucial to improve our ability to predict the impact of intraguild predation on community structure and, from an applied perspective, biological control.     

Impacts of elevated CO2 on Bemisia tabaci infesting Bt cotton and its parasitoid Encarsia formosa

Atmospheric carbon dioxide concentration is expected to rise in the coming decades. Rising atmospheric CO₂ levels may alter plant‐insect‐parasitoid associations due to the indirect effects of CO₂ enrichment on phytochemicals important for herbivore and parasitoid nutrition. Tritrophic effects of elevated CO₂ on Bt cotton (GK‐12) and non‐transgenic (Simian‐3, or S3) cotton [Gossypium hirsutum L. (Malvaceae)], Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), and its parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae), were examined in open‐top chambers. Significantly, longer egg‐adult developmental duration and higher mortality of nymphs were observed under elevated CO₂ concentrations on both cotton cultivars during three successive generations. However, no significant differences were found in adult longevity, offspring sex ratio, and the number of eggs laid per female adult of B. tabaci fed on transgenic (GK‐12) or non‐transgenic cotton (S3) grown under elevated CO₂. Abundance of B. tabaci adults increased from 10 to 120 per plant and then decreased to 40 per plant through the growing season, but no significant differences in density occurred between CO₂ treatments and between cultivar treatments. Similarly, no significant differences were found in the developmental duration, parasitization rate, and adult emergence rate of E. formosa after parasitizing B. tabaci for three successive generations. Our results showed that the effects of transgenic Bt cotton did not significantly affect the development, survivorship, life span, or fecundity of B. tabaci and its parasitoids. Moreover, interactions between B. tabaci and E. formosa were not significantly affected by elevated CO₂. These results suggest that the biological control of B. tabaci by E. formosa would not be influenced by transgenic Bt cotton and/or elevated CO₂, indicating that the current risk management strategy regarding B. tabaci outbreaks and biocontrol by E. formosa will remain effective if the atmospheric CO₂ level continues to rise.     

Stink bug rostrum length vs. stylet penetration potential

Stink bugs (Hemiptera: Pentatomidae) and related species continue to plague cotton, Gossypium hirsutum L. (Malvaceae), worldwide. Stink bugs utilize their stylets (housed within the rostrum) to feed upon cotton bolls and transmit pathogens that cause seed and boll rot of cotton. Stylet penetration potential of stink bugs is influenced by species and recent observations indicated a phenomenon whereby stink bugs with shorter rostra yielded deeper stylet penetration estimates. The objective of this study was to elucidate the relationship between rostrum length and known stylet penetration estimates for two pairs of similar‐sized pentatomid species: Chinavia hilaris (Say) vs. Euschistus servus (Say), and Oebalus pugnax (Fabricius) vs. Piezodorus guildinii Westwood. For each species, individual rostral segments were measured to yield total lengths, and measurements were compared against known stylet penetration estimates. Chinavia hilaris and P. guildinii have longer rostra than E. servus and O. pugnax, respectively, yet E. servus and O. pugnax yielded deeper stylet penetration estimates. Deeper stylet penetration by species with shorter rostra can be attributed to differences in the lengths of rostral segments 1 and 2. Euschistus servus and O. pugnax each had significantly longer rostral segments 1 and 2 than C. hilaris and P. guildinii, respectively. Also, the cumulative lengths of rostral segments 1 and 2 comprised a higher overall proportion of the entire rostrum length in E. servus and O. pugnax vs. C. hilaris and P. guildinii, respectively. Rostral segments 1 and 2 are instrumental in the feeding mechanics of these phytophagous species; it is clear that their greater length and their role in stylet penetration model calculations – including the lengths of segments 3 and 4 – override the presumption that total rostrum length equates to stylet penetration potential. This novel finding contributes to the general knowledge of stink bug feeding mechanics.     

Predation of cotton bollworm by green lacewings in the presence of cotton aphid as alternative prey on transgenic Bt and conventional cotton

Experiments were conducted in small arenas and on whole plants to explore the effect of cotton aphids, Aphis gossypii Glover (Hemiptera: Aphididae), as alternative prey on the predation of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) larvae by green lacewing larvae, Mallada signatus Schneider (Neuroptera: Chrysopidae). Transgenic Bt (Bollgard II^®) and conventional cotton plants were included to explore potential differences in the predator's performance on these cotton types. In small arenas, the presence of 20 aphids reduced predation on H. armigera larvae by 22% (from 5.5 to 3.3 of 10) by a single lacewing larva over a 24‐h period. The presence of H. armigera reduced predation on aphids by ca. 29% (from 16.8 to 11.0 of 20) over 24 h. On whole plants, the presence of alternative prey had no effect on the number of H. armigera larvae or aphids remaining after 3 days. The presence of H. armigera larvae alone, without the predator, caused a 24% reduction in the numbers of aphids on conventional, but not on Bt cotton plants. The combination of Bt cotton and lacewing larvae caused a 96.6% removal of early‐stage H. armigera larvae, a statistically significant increase over the addition of the proportions (91.6%) removed by each factor measured separately, providing evidence of synergism. These studies suggest that the presence of aphids as alternative prey would not necessarily disrupt the predation by green lacewing on larvae of H. armigera, especially on Bt cotton.     

Depressed performance and detoxification enzyme activities of Helicoverpa armigera fed with conventional cotton foliage subjected to methyl jasmonate exposure

Methyl jasmonate (MeJA)‐mediated defense in conventional cotton, Gossypium hirsutum L. (Malvaceae), against cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), was investigated with respect to the activities of the detoxification enzymes acetylcholinesterase (AChE), carboxylesterase (CarE), and glutathione S‐transferases (GST) in pupae as well as the performance of larvae. The results suggested that exogenous application of MeJA to cotton leaves depressed the activities of AChE, CarE, and GST of cotton bollworm pupae. Both the absolute and protein‐specific AChE activities of pupae were depressed at all three MeJA concentrations applied as compared with a control, and the effects of 0.4 mM MeJA were significantly higher than those of 0.1 and 0.2 mM. A marked reduction in absolute CarE activity was observed at the 0.4 mM MeJA treatment, whereas the protein‐specific activity was increased by 0.2 and 0.4 mM. Absolute GST activity was significantly depressed only by the 0.4 mM MeJA treatment, whereas protein‐specific GST activity was not markedly affected by MeJA. Protein content of pupae was reduced by 0.4 mM MeJA‐induced defense in cotton leaves. The development time of larvae was protracted and pupal weight was reduced by 0.1 and 0.4 mM MeJA‐treated cotton leaves. Larval weight gain was inhibited significantly on 0.2 and 0.4 mM MeJA‐treated cotton leaves. The results suggested that MeJA‐induced plant defense may have adverse effects on H. armigera. In addition to the inhibition of growth and development, induced defense may also impair the insect's ability to detoxify toxic plant secondary metabolites.     

Quantifying insect predation with predator exclusion cages: the role of prey antipredator behavior as a source of bias

There are limitations imposed by current methodologies to detect and quantify insect predation. However, there has been relatively little effort to experimentally document the sources of biases associated with the various methodologies. In this study, we examined how predation estimates in the field using predator exclusion cages may be biased when one fails to account for antipredator behavioral responses. To do this, we did the usual comparison of the number of insects missing from plants where predators were allowed access to the number missing from plants where predators were excluded, but also determined how many of the missing insects reacted to predators by dropping from plants and how many were actually preyed upon. Our results provide evidence that estimates of insect mortality in the field are significantly reduced if prey antipredator behavior is taken into account. As it is commonly assumed that prey missing in the field are predated, documenting the incidence of predator‐mediated ‘disappearance’ and capturing insect prey before they escape can provide with a relevant estimate of bias.     

Yield,development, and quality response of dual‐toxin Bt cotton to Helicoverpa spp. infestations in Australia

To verify current thresholds for Bollgard II^® cotton in Australia, the impact of Helicoverpa spp. (Lepidoptera: Noctuidae) larvae on yield, development, and quality under various infestation intensities and durations, and stages of growth, was tested using small plot field experiments over two seasons. Infestation with up to 80 eggs m^?1 of Helicoverpa armigera (Hübner) and Helicoverpa punctigera Wallengren showed that species, infestation level, and stage of growth had no significant effect on yields of seed‐cotton or lint and on maturity and fibre quality. The duration of infestation of white flowers with H. punctigera neonates (maximum of every day for up to 4 weeks) had no impact on the yield of seed‐cotton or lint, maturity, and fibre quality, but when 100% of flowers were infested (compared with 0 or 50%), seed‐cotton and lint yields were significantly reduced and maturity was delayed. Infestation with up to 18 medium H. armigera larvae m^?1 at several plant stages did not significantly affect yields of seed‐cotton and lint, maturity, and fibre quality. A heliocide spray applied on a commercial farm at the current threshold resulted in a significantly higher lint yield, compared with a farm where no spray was applied. In conclusion, Bollgard II^® cotton is highly resistant to Helicoverpa spp. infestation.     

Climate change and trophic interactions in model temporary pond systems: the effects of high temperature on predation rate depend on prey size and density

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Effects of carotenoid sequestration on a caterpillar's cryptic coloration and susceptibility to predation

Carotenoids are used for many functions by animals, including combining with other pigments to produce aposematic and cryptic coloration. Carotenoids in combination with blue pigments are responsible for green coloration in many caterpillars, and thus carotenoid sequestration may reduce their contrast against a green foliage background. We tested the hypothesis that carotenoid sequestration reduces contrast and enhances survival by rearing Trichoplusia ni Hübner (Lepidoptera: Noctuidae) on Brassica oleracea L. var. Acephala (Brassicaceae) leaves and exposing them to predators. We found that carotenoids derived from the host plant are partially excreted, along with chlorophyll, but also sequestered in hemolymph. Larvae that were given plants that provided carotenoids showed less contrast against their host plants within 1 day compared to larvae that were not provided with carotenoids. Last, both short‐term field observations and laboratory trials of larvae caged with predatory Podisus maculiventris Say (Hemiptera: Pentatomidae) nymphs showed that survival of carotenoid‐sequestering larvae was higher compared to larvae that did not sequester. These results suggest that carotenoid sequestration may be an important adaptive strategy that reduces susceptibility to natural enemies that hunt by sight. Further research that examines the mechanisms by which carotenoids are absorbed and modified will lend insights into the evolution of carotenoids functioning as passive defensive compounds.     

Orientation behavior of Propylaea japonica toward visual and olfactory cues from its prey–host plant combination

The lady beetle Propylaea japonica (Thunberg) (Coleoptera: Coccinellidae) is an important predator of aphids in agroecosystems. The inundative release of coccinellid beetles can be an effective biological control strategy. An understanding of how biological control agents perceive and use stimuli from host plants is the key to successfully implement commercially produced predators. Here, we studied the relative role of visual and volatile cues. Dual‐choice assays using foraging‐naïve and foraging‐experienced P. japonica adults were conducted using cotton plants [Gossypium hirsutum L. (Malvaceae)] with or without infestation by the cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae). Overall, experienced beetles were more attracted than naïve beetles toward cues associated with aphid‐infested plants. Experienced beetles were also more responsive to olfactory cues compared with naïve beetles. Both foraging‐naïve and ‐experienced lady beetles integrate olfactory and visual cues from plants infested with aphids, with an apparently greater reliance on olfactory cues. The results suggest that foraging experience may increase prey location in P. japonica.     

Intraguild predation and cannibalism among Dicyphini: Dicyphus cerastii vs. two commercialized species

Dicyphine mirids are one of the most important groups of predators on tomato. In the Mediterranean region, several species in the genera Dicyphus, Macrolophus, and Nesidiocoris (Hemiptera: Miridae, Bryocorinae, Dicyphini) colonize protected horticultural crops. In Portugal, Nesidiocoris tenuis (Reuter) is increasingly abundant in the mirid species complex of tomato crops and appears to be displacing the native Dicyphus cerastii Wagner. In order to know whether intraguild predation (IGP) can explain the decreasing abundance of D. cerastii, we evaluated predatory interactions between adult females and first instars of D. cerastii vs. N. tenuis but also D. cerastii vs. Macrolophus pygmaeus (Rambur), as this species is also naturally present in horticultural crops in Portugal. Cannibalistic interactions were also tested for the same three species. All experiments were performed under laboratory conditions, in Petri dish arenas, in the presence or absence of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as alternative prey. Predation on both heterospecific and conspecific nymphs occurred only in the absence of alternative food. Intraguild predation was mutual and symmetrical between D. cerastii and M. pygmaeus. However, IGP was asymmetrical between D. cerastii and N. tenuis, favouring the first. Cannibalism was not significantly different among these mirid species. Our results show that D. cerastii has a greater capacity to feed on intraguild prey than N. tenuis. Therefore, IGP on small nymphs does not explain the abundance shift between D. cerastii and N. tenuis.     

Elevational contrast in predation and parasitism risk to caterpillars in a tropical rainforest

Invertebrate predators and parasitoids are among the most important natural enemies of insect herbivores. Yet, the strength of natural enemy pressure along an altitudinal gradient and interactions between the groups of natural enemies (such as predation on parasitized prey) are not well known. Various methods are used to reveal the mortality factors of herbivores. Predation pressure is usually assessed through exposure of artificial prey. However, this method cannot provide information about the attacks of parasitoids, or their eventual interactions with predators. Furthermore, artificial or dead prey might not attract predators because they do not show expected host behavior, and this method mostly cannot distinguish between predation and scavenging. For the first time in a tropical rainforest, we quantified elevational contrast in mortality factors using exposure of live caterpillars. We exposed a total of 800 live caterpillars of Talanga excelsalis moresbyensis Strand (Lepidoptera: Crambidae) on saplings of Ficus copiosa Steud. (Moraceae) at two elevations in primary tropical rain forest in Papua New Guinea (200 and 1 200 m a.s.l.). We exposed the caterpillars in two treatments: exposed to and protected from invertebrate predators and parasitoids. Disappearance of caterpillars was significantly higher in the exposed treatment. Furthermore, caterpillar disappearance was significantly higher in lowlands than in highlands (43 vs. 12%). We consider the vast majority of the disappearance to be due to predation, as migration of the caterpillars from the focal trees was not observed (except one caterpillar). This estimate of invertebrate predation rate corresponds with studies which used artificial caterpillar models. No significant difference in parasitism rate between the two elevations was observed (12 vs. 13%). The combination of the disappearance and parasitism rate patterns means that larval parasitoids face stronger pressure from invertebrate predators through higher predation of their hosts in the lowlands than in the highlands.     

Intra‐ and interspecific interactions between aphidophagous ladybirds: the role of prey in predator coexistence

Cannibalism (CANN) and intraguild predation (IGP) may provide energy and nutrients to individuals and eliminate potential competitors. These negative competitive interactions could also affect the coexistence of predatory species. The co‐occurrence of aphidophagous ladybird species in crops creates opportunities for CANN and IGP, especially when aphids become scarce. The Lotka–Volterra model predicts the coexistence of two species if intraspecific competition is stronger than interspecific interference interactions. Cycloneda sanguinea L. and Eriopis connexa (Germar) (both Coleoptera: Coccinellidae) coexist in sweet pepper crops in La Plata (Argentina) consuming mainly Myzus persicae (Sulzer) (Hemiptera: Aphididae). The present study used laboratory experiments to estimate levels of CANN and IGP by adults and larvae on eggs, and by adults on larvae, in both the presence and absence of prey (i.e., M. persicae), to explain the effect of prey on coexistence of these two predators. Levels of CANN by C. sanguinea and E. connexa were high in the absence of aphids, and decreased when prey was present. Intraguild predation was bidirectional and asymmetric. Adults and larvae of E. connexa were more voracious IG predators of C. sanguinea than vice versa, the former being the stronger IG predator and interference competitor. Eriopis connexa always won when larvae of the same instar were compared, whereas the larger larva always won when larvae were of different instars, regardless of species. In the presence of prey, CANN by both species decreased, but IGP by E. connexa on C. sanguinea remained high, suggesting that E. connexa could displace C. sanguinea via interspecific interference competition. Other factors potentially affecting the coexistence of C. sanguinea and E. connexa in sweet pepper crops are discussed.     

Constitutive exposure to the volatile methyl salicylate reduces per‐capita foraging efficiency of a generalist predator to learned prey associations

Understanding the factors that influence the ability of predators to find and kill herbivores is central to enhancing their impact on prey populations, but few studies have tested the impact of these factors on predation rates in realistic foraging environments. Using the tri‐trophic system consisting of tomato, Solanum lycopersicum L. (Solanaceae), hornworm caterpillars, Manduca sexta L. (Lepidoptera: Sphingidae), and the predaceous stink bug Podisus maculiventris (Say) (Hemiptera: Pentatomidae), we measured the effects of associative learning and plant volatile camouflage on predator behavior and foraging efficiency in field enclosures. To do so, we compared experienced vs. naive individuals under varying environmental contexts. Experienced predators were those with prior exposure to induced volatiles from the tomato–caterpillar association, whereas naive predators had not experienced tomato, only prey (caterpillars). We varied their environmental foraging matrix using either (1) tomato surrounded by basil (Ocimum basilicum L.; Lamiaceae) or (2) tomato exposed to the synthetic volatile, methyl salicylate (MeSA). We found that (1) experienced predators were more efficient than naive predators, capturing 28% more prey; (2) the tomato–basil combination did not affect predator–prey interactions; and (3) constitutive emission of synthetic MeSA caused a 22% reduction in P. maculiventris predation rate. These differences corresponded with distinct shifts in predator foraging; for example, experienced individuals were less stationary and exhibited unique behaviors such as stylet extension. Taken together, these results suggest that it is possible to improve the function of generalist predators in suppressing prey by coupling odors with food. However, constitutive emission of volatiles to attract natural enemies may ultimately camouflage neighboring plants, reducing the benefits of orientation to learned stimuli such as induced volatiles.