Genetic variation in defensive chemistry in Plantago lanceolata (Plantaginaceae) and its effect on the specialist herbivore Junonia coenia (Nymphalidae)

To examine genetic variation in defensive chemistry within and between natural populations of Plantago lanceolata, we performed a greenhouse experiment using clonal replicates of 15 genotypes from each of two populations, from a mowed lawn and an abandoned hayfield. Replicates of each genotype were harvested for determinations of aboveground biomass and leaf chemical content either at the beginning of the experiment (initial controls), after exposure to herbivory by larvae of Junonia coenia, a specialist on P. lanceolata (herbivory treatment), or at the end of the experiment without exposure to herbivory (final controls). Allocation to the iridoid glycosides aucubin and catalpol and the phenylpropanoid glycoside verbascoside displayed significant genetic variation within and between populations, and differed with leaf age. Significant genotypextreatment interactions indicated genetic variation in response of leaf chemistry to the treatments. There was no evidence for a cost of allocation to chemical defense: genetic correlations within and between chemical pathways and between defensive chemicals and aboveground growth were positive or nonsignificant. Although iridoid glycosides are known to be qualitative feeding stimulants for J. coenia, multiple regression of larval survivorship on leaf chemical content and shoot biomass indicated that larvae had lower survivorship on P. lanceolata ge-notypes with higher concentrations of aucubin in the leaves. Larval survivorship was unaffected by levels of catalpol and verbascoside. Thus, although specialist herbivores may respond to defensive chemicals as qualitative feeding stimulants, they do not necessarily have higher fitness on plant genotypes containing higher concentrations of these chemicals.     

The genetic basis of altitudinal variation in the wood frog Rana sylvatica II. An experimental analysis of larval development

Summary The variation in larval developmental patterns in the wood frog, Rana sylvatica, along an elevation gradient of 1,000 m was experimentally studied. Larval populations at high elevation ponds had lower growth rates, developmental rates and were larger at all stages (including metamorphic climax) than larval populations developing in low elevation ponds. There was considerable variation among ponds within each elevation in both the length of the larval period and size at metamorphic climax. Reciprocal transplant experiments and controlled laboratory experiments revealed that most of the observed variation between high and low elevation populations could be explained by the effects of temperature induction during ontogeny. Significant genetic differences in growth rates and non-genetic maternal effects on developmental rates between larvae of mountain origin and lowland origin were also demonstrated. Selection in both environments has acted to minimize the prevailing environmental effect of pond temperature on developmental rates, but has accentuated the prevailing environmental effects on larval body size. As a consequence mountain larvae were capable of completing metamorphosis sooner and at a larger size in all environments than lowland larvae.     

Effects of aphid-tending Argentine ants, nitrogen enrichment and early-season herbivory on insects hosted by a coastal shrub

The presence of the exotic Argentine ant, Linepithema humile Mayr (Hymenoptera: Dolichoderinae), nitrogen enrichment, and early-season herbivory by the specialist beetle Trirhabda bacharidis (Coleoptera: Chrysomelidae) have been shown, through separate experiments, to affect the densities of insect herbivores of the coastal shrub Baccharis halimifolia (Asteraceae), in Florida. Using a fully-factorial field experiment, we examined the relative importance of all three of these factors to the six most common insect herbivore species utilizing this host plant in a West Central Florida coastal habitat. The presence of ants affected more herbivore species than either early-season herbivory by larval T. bacharidis or nitrogen enrichment. Experimental reductions of L. humile resulted in reductions of an aphid, its coccinellid predators, and adult T. bacharidis, and increases of two species of leafminers and one species of stemborer. Due to the strong negative effects of stemborer herbivory on host plant survival, the increase in stemborer abundance led to increased host plant mortality. Early-season herbivory by larval T. bacharidis only affected the abundance of aphids and their predators, both of which were more abundant on trees with reduced early-season herbivory. Nitrogen fertilization had the most limited effects and only T. bacharidis larvae achieved higher densities on fertilized trees. Our results indicate that aphid tending by the exotic L. humile affects other insects on B. halimifolia more so than herbivory by the exploitative competitor T. bacharidis or nitrogen as a limiting nutrient.     

Environmental and genetic control of insect abundance and herbivory along a forest elevational gradient

Environmental conditions and plant genotype may influence insect herbivory along elevational gradients. Plant damage would decrease with elevation as temperature declines to suboptimal levels for insects. However, host plants at higher elevations may exhibit traits that either reduce or enhance leaf quality to insects, with uncertain net effects on herbivory. We examined folivory, insect abundance and leaf traits along six replicated elevational ranges in Nothofagus pumilio forests of the northern Patagonian Andes, Argentina. We also conducted a reciprocal transplant experiment between low- and high-elevation sites to test the extent of environmental and plant genetic control on insect abundance and folivory. We found that insect abundance, leaf size and specific leaf area decreased, whereas foliar phosphorous content increased, from low-, through mid- to high-elevation sites. Path analysis indicated that changes in both insect abundance and leaf traits were important in reducing folivory with increasing elevation and decreasing mean temperature. At both planting sites, plants from a low-elevation origin experienced higher damage and supported greater insect loads than plants from a high-elevation origin. The differences in leaf damage between sites were twofold larger than those between plant origins, suggesting that local environment was more important than host genotype in explaining folivory patterns. Different folivore guilds exhibited qualitatively similar responses to elevation. Our results suggest an increase in insect folivory on high-elevation N. pumilio forests under future climate warming scenarios. However, in the short-term, folivory increases might be smaller than expected from insect abundance only because at high elevations herbivores would encounter more resistant tree genotypes.     

Ungulate herbivory reduces abundance and fluctuations of herbivorous insects in a boreal old-growth forest

Ecological theory predicts the strongest ecosystem effects of herbivory when dominant and ecologically important species are consumed. Bilberry, Vaccinium myrtillus, is such a key plant species, attractive to many other species in the boreal forests, for example ungulate and invertebrate herbivores. Large herbivores may remove substantial biomass and alter plant quality and therefore affect abundance and populations of invertebrate animals sharing the same food plant. We combined experimental exclusion of ungulates with a browsing intensity gradient to investigate the 15-year effect of ungulate (Cervus elaphus and Ovis aries) browsing on bilberry plant size and on bilberry-feeding herbivorous larvae (Lepidoptera and Symphyta), in a Norwegian old growth boreal forest ecosystem. Bilberry ramets in exclosure plots had nearly nine times higher dry mass and three times higher abundance of invertebrates feeding on them than in ungulate-access plots. Sweep-netting data verified these findings as larval numbers were twice as high in exclosure plots. The pattern in the large herbivore effects on bilberry size and abundance of herbivorous larvae were identical along the browsing gradient. Differences in larval abundance between treatments, as indicated by leaf-chewing, increased during the 15-year study period, and the community fluctuations were larger when ungulate herbivores were excluded. The browsing effect was moderated by plant quality as larval densities were lowest on both heavily-browsed and non-browsed plants, and highest on ramets that had 50–74% of annual shoots browsed. Our study supports previous findings in that bilberry is relatively disturbance tolerant and may recover quickly, but that ungulates may compete with herbivorous larvae for food biomass. Additionally, our results strongly indicates that population insect community peaks and fluctuations are dampened by ungulate consumption. Our findings add to the understanding on how ungulates may structure forest ecosystems directly and indirectly.     

Performance of moth larvae on birch in relation to altitude, climate, host quality and parasitoids

We studied topographical and year-to-year variation in the performance (pupal weights, survival) and larval parasitism of Epirrita autumnata larvae feeding on mountain birch in northernmost Finland in 1993–1996. We found differences in both food plant quality and parasitism between sites ranging from 80 m to 320 m above sea level. Variation in food plant quality had particularly marked effects on larval survival. The advanced phenology of the birches in relation to the start of the larval period reduced pupal weights. Parasitism rates were different between years and between sites. The clearest site differences were in the proportions of different parasitoid species: Eulophus larvarum was most abundant at the lowest-altitude sites, and Cotesia jucunda at the highest. Differences in the performance of E. autumnata were related to temperature conditions: at higher temperatures, survival and the egg production index were lower, and larval parasitism was higher than at lower temperatures. The higher parasitism at higher temperatures was probably due to greater parasitoid activity during warmer days. In the comparison of different sources of spatial and annual variation in the performance of E. autumnata, the most important factor appeared to be egg mortality related to minimum winter temperature, followed by parasitism and, finally, the variation in food plant quality. If, as predicted, the climate gradually warms up, the effects of warmer summers on the outbreaks of E. autumnata suggest a decrease in outbreak intensity. Received: 4 January 1999 / Accepted: 22 March 1999     

Residence time and drift patterns of larval June sucker Chasmistes liorus in the lower Provo River as determined by otolith microstructure

Estimates of age derived from daily ring counts from otoliths and capture rates of larval June sucker Chasmistes liorus were used to determine the relationship between discharge rates of the Provo River and residence time and patterns of larval drift. During 1997, larval drift occurred over a 22 day period when discharge rates were low (mean ±s.d. 3·2 ± 0·0 m³ s^?1). In 1998, larval drift occurred in two separate events over a 40 day period. Discharge was higher during the first larval drift period (19 days; 24·8 ± 1·3 m³ s^?1) and lower during the second larval drift period (17 days; 7·0 ± 0·9 m³ s^?1). In 1997, no larval fish were collected at the lowermost transect on the Provo River (nearest Utah Lake), and few larvae >21 days of age were found. During the first drift period of 1998, larval C. liorus were collected at all transects, and mean age of larvae collected between upstream and downstream transects increased by c. 7 days. During the second drift period of 1998, only a few were collected in the lowermost transects, and age did not increase with proximity to the lake. Patterns in catch and age distribution of larval C. liorus in the lower Provo River suggest that recruitment failure occurs during the larval drift period in years with insufficient discharge to transport larvae into the lake.     

Herbivory and pollen limitation at the upper elevational range limit of two forest understory plants of eastern North America

Studies of species' range limits focus most often on abiotic factors, although the strength of biotic interactions might also vary along environmental gradients and have strong demographic effects. For example, pollinator abundance might decrease at range limits due to harsh environmental conditions, and reduced plant density can reduce attractiveness to pollinators and increase or decrease herbivory. We tested for variation in the strength of pollen limitation and herbivory by ungulates along a gradient leading to the upper elevational range limits of Trillium erectum (Melanthiaceae) and Erythronium americanum (Liliaceae) in Mont Mégantic National Park, Québec, Canada. In T. erectum, pollen limitation was higher at the range limit, but seed set decreased only slightly with elevation and only in one of two years. In contrast, herbivory of T. erectum increased from <10% at low elevations to >60% at the upper elevational range limit. In E. americanum, we found no evidence of pollen limitation despite a significant decrease in seed set with elevation, and herbivory was low across the entire gradient. Overall, our results demonstrate the potential for relatively strong negative interactions (herbivory) and weak positive interactions (pollination) at plant range edges, although this was clearly species specific. To the extent that these interactions have important demographic consequences—highly likely for herbivory on Trillium, based on previous studies—such interactions might play a role in determining plant species' range limits along putatively climatic gradients.     

The unique interaction between the summer annual desert plant Salsola inermis Forssk and weevils residing on its roots: mutualism or parasitism?

1. Herbivores and parasites are likely to impose less damage on their host when their growth rate is slow and their dependency on the host is high. Accordingly, it was hypothesised that evolution would favour neutral or even beneficial interactions between a below-ground herbivore and a plant during the harsh season in a desert ecosystem. 2. This study characterised the relationship between the summer annual plant Salsola inermis Forssk (Chenopodiaceae) and weevils developing in a mud chamber attached to its roots in the Negev Desert of Israel. Plant seedlings were exposed to adult weevils (Conorhynchus palumbus Olivier or Menecleonus virgatus Schoenherr; Coleoptera: Curculionidae) in a controlled outside setting, to induce oviposition and larval establishment. The following were quantified: plant growth, above-ground biomass, fruit biomass, and fruit size, as well as relative C and N contents, and isotopic signatures (δ¹³C and δ¹⁵N) in plant tissues. 3. Exposure to weevils did not reduce plant survival but significantly and negatively affected plant growth and seed production. However, these effects were mainly due to above-ground herbivory by adults rather than root herbivory by larvae, and might have been overestimated. Interestingly, %N and δ¹⁵N were significantly higher, and the C:N ratio was significantly lower, in plants with larval establishment, suggesting that weevils affect the plant nitrogen budget. 4. The overall results do not support the notion of mutualistic interactions; yet, slow consumption, a low infestation level, and, possibly, N supplementation to the plant may enable the plant to tolerate herbivory under natural conditions.     

Effects of bird predation on arthropod abundance and tree growth across an elevational gradient

Considerable uncertainty surrounds the conditions under which birds can cause trophic cascades. In a three‐year experiment, we studied the direct and indirect effects of insectivorous birds on arthropod abundance, herbivory, and growth of striped maple Acer pensylvanicum saplings in a northern hardwood forest of central New Hampshire, USA. We manipulated bird predation by erecting exclosures around saplings and directly manipulated herbivory by removing herbivores. We also examined how climate modifies these interactions by replicating the experiment at three locations along an elevational gradient. Effects of bird predation were variable. Overall, mean arthropod biomass was 20% greater on saplings within bird exclosures than on controls (p<0.05). The mean biomass of leaf‐chewing herbivores, primarily Lepidoptera larvae, was 25% greater within exclosures but not statistically different from controls. To a lesser degree, mean herbivore damage to foliage within exclosures exceeded that of controls but differences were not significant. We also did not detect significant treatment effects on sapling shoot growth. The high understory vegetation density relative to bird abundance, and low rate of herbivory during the study (mean 5% leaf area removed, controls), may have limited the ability of birds to affect sapling growth. Climate effects operated at multiple scales, resulting in a complex interplay of interactions within the food web. Regional synchrony of climatic conditions resulted in annual fluctuations in herbivore abundance and tree growth that were shared across elevations. At the same time, local environmental variation resulted in site differences in the plant, herbivore, and bird communities. These patterns resulted in a mosaic of top–down strengths across time and space, suggesting an overall pattern of limited effects of birds on plant growth, possibly interspersed with hotspots of trophic cascades.     

The effect of rainfall on tick challenge at Kyle Recreational Park,Zimbabwe

The effect of rainfall pattern on tick challenge was investigated at Kyle Recreational Park, Zimbabwe, from 1991 to 1992 using drag and removal plot methods to sample environmental tick density. The abundance of adults and nymphs of the brown ear-tick Rhipicephalus appendiculatus and larvae of the bont tick Amblyomma hebraeum was positively correlated with monthly rainfall, whereas no relationship with rainfall was revealed for larval R. appendiculatus, adults of the red-legged tick R. evertsi, or larvae of the blue tick Boophilus decoloratus. A comparison between 1991 (490 mm rainfall) and the drought year of 1992 (161 mm) revealed significant differences in the abundance of R. appendiculatus, A. hebraeum, and B. decoloratus. During the wet season, R. appendiculatus adults were 2–3 time more numerous in the environment during the higher rainfall year of 1991. A. hebraeum larval abundance exhibited a similar pattern to that of R. appendiculatus adults, but B. decoloratus larvae were more abundant in the drought year of 1992 during both the wet and dry seasons. Comparable tick abundance data collected at Kyle during the above-average rainfall years of 1975–1977 (mean = 1029 mm) were compared with tick challenge during the below-average rainfall years of 1991–1992 (mean = 326 mm). In grassland sand habitat and all habitats combined R. appendiculatus adults, nymphs, and larvae were much more abundant during the high rainfall years. In contrast, larvae of B. decoloratus were more numerous during the drier years. A. hebraeum larvae were also more abundant during the drier years. The strong positive correlation of adult R. appendiculatus abundance with rainfall and the coincidence of increased adult tick challenge with increased rainfall indicates that adult R. appendiculatus tick burden on hosts would be heaviest during the wet season and high rainfall years.     

Factors affecting calculation of nutritional induces for foliage-fed insects: an experimental approach

To determine how nutritional indices for insects fed leaves are affected by the experimental conditions and the physiology of the plant material, we used larvae of the buckmoth, Hemileuca lucina Hy. Ed. (Saturniidae) and their hostplant Spiraea latifolia Ait. Bork (Rosaceae). Under experimental conditions identical to those used to determine larval nutritional indices, we found that the age of leaves (new versus mature) significantly affected their metabolism and water loss, but simulated herbivory did not directly affect leaf metabolism. Over a 6-day test, nitrogen concentration showed an initial increase followed by a gradual decline, and was higher in new leaves compared to mature leaves. New leaves increased in protein concentration and then gradually returned to the initial level, whereas mature leaves changed little over the 6-day test. These changes in percent nitrogen and protein may largely reflect the disproportional changes in non-nitrogenous materials. Solitary and grouped larvae had similar growth rates on new leaves, but they differed on mature leaves. Deliberate manipulation of larvae during the course of an experiment significantly reduced relative growth rates by increasing duration of the stadium rather than by decreasing biomass gained. Two methods of estimating larval gut contents at mid-stadium were compared: weight of frass produced and weight of digestive tract and contents. After the end of the 4-day test period used to determine nutritional indices, the digestive tracts with food accounted for 10.8% of the larval dry weight. Larval frass produced in 24 h after the end of the test period comprised 9.3% of the larval dry weight. Correction factors for plant metabolism changed nutritional indices by 1 to 8%, while those for larval gut contents altered indices by 2 to 15%.     

Fine‐tuning of defences and counter‐defences in a specialised plant–herbivore system

1. The plant–herbivore arms race has been postulated to be a major driver for generating biological and biochemical diversity on Earth. Herbivore feeding is reduced by the production of chemical and physical barriers, but increases plant resistance against subsequent attack. Accordingly, specialisation is predicted to be an outcome of herbivores being able to circumvent plant‐induced defences. 2. Using a specialised plant–herbivore system, in which adult chrysomelid beetles (Chrysochus auratus) feed on leaves and larvae feed on roots of dogbane (Apocynum spp.), this study investigated whether root latex and cardenolides are effective against the soil‐dwelling larvae, and whether such defences could be circumvented by the herbivore. 3. Across two Apocynum species, C. auratus larvae were not affected by latex production or cardenolide amounts and diversity. By contrast, cardenolide apolarity was detrimental to larval growth. Yet larval feeding decreased average root cardenolide apolarity in A. cannabinum and larvae performed better on those plants. Finally, above‐ground induction rendered the plants more toxic by increasing root cardenolide apolarity and maintaining it, even during subsequent larval herbivory. 4. Therefore, the intimate relationship and interaction between Chrysochus and Apocynum are maintained by a delicate balance of herbivore manipulation and plant chemical induction.     

The influence of pre‐settlement and early post‐settlement processes on the adult distribution and relative dominance of two invasive mussel species

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First report of Avicennia germinans (Acanthaceae) as a larval host of Junonia litoralis (Nymphalidae) causing higher foliar damage in seedlings than trees

Herbivory is considered an important biotic interaction in mangroves. Nevertheless, detailed information on specific plant–herbivore interactions that might have considerable influence in ecological and evolutionary processes is still very poor and fragmented. Herbivory damage was quantified during December 2015 in seedlings and trees in monospecific stands of Avicennia germinans in Laguna Madre of Tamaulipas, Mexico. The use of this mangrove species as a larval host is well documented; however, this is the first report for Junonia litoralis. These lepidopteran larvae consumed, on average, 10.2% of the leaf area; but herbivory was higher on seedlings (mean 15%) than on trees (mean 2.3%). These values are comparable to estimations of 10% mean herbivory damage in other field studies. This indicates that herbivores cause greater damage in seedlings than in trees. Herbivore activity by J. litoralis only occurred in A. germinans and did not affect associated herbs or shrubs of other species. The close interaction between J. litoralis and A. germinans may have profound implications for ecological and evolutionary processes of mangroves and enables a better understanding of ecosystem function and its conservation. Further studies are needed to investigate such interactions and their implications including long-term monitoring of interstitial salinity and leaf chemistry at different stages of growth and maturity of the host species.     

The Herbivore Assemblage, Herbivory and Leaf Chemistry of the Mangrove Kandelia obovata in Two Contrasting Forests in Hong Kong

The herbivore assemblage, intensity of herbivory and factors determining herbivory levels on the mangrove Kandelia obovata (previously K. candel, Rhizophoraceae) were studied over a 13-month period at two forests with contrasting growing conditions in Hong Kong. Mai Po was part of an eutrophic embayment in the Pearl River estuary and generally offered more favourable conditions for mangrove growth, whereas Ting Kok had a rocky substratum and oceanic salinity. Twenty-four insect herbivore species were recorded on K. obovata, with lepidopteran larvae that consume leaf lamina being the dominant species. While leaf litter production was similar at the two forests, herbivory level at Mai Po (mean = 3.9% in terms of leaf area loss) was more severe than that at Ting Kok (mean = 2.3%). Peak herbivory levels were found in summer at both locations (6.5% for Mai Po and 3.8% for Ting Kok). Young leaves of K. obovata at both locations were generally preferred by the herbivores from the period of late spring to summer. Concentrations of most feeding deterrents (ash, crude fibre, and total soluble tannins) were significantly higher in both young and mature leaves at Ting Kok, whereas leaf nutrients (total nitrogen and water) were the same at the two sites. Young leaves at Ting Kok contained about 30% more tannins than their counterparts at Mai Po. Significant differences in leaf chemistry also existed between young and mature leaves at either site. The differences were concomitant with the observed patterns of leaf herbivory on K. obovata, and suggest a potential relationship between environmental quality and plant defence against herbivory.     

Numerical and temporal relationships in a three-level food chain

Summary Densities were examined in natural populations consisting of horsenettle (Solanum carolinense), larvae of a horsenettle-specific phytophagous moth (Frumenta nundinella), and a polyphagous parasitoid wasp (Scambus pterophori), that parasitized the moth. Herbivore and parasitoid densities were both positively associated with fruit density, but moth larval density was linear while parasitoid density increased parabolically; thus, optimum moth survivorship was at intermediate moth densities. There was no evidence of escape from herbivory in time by plant populations due to either mean flowering date or a spread of flowering in seasonal time. However, one plant population and one moth population apparently escaped in space due to isolated location. Although plant reproductive success is reduced whether or not moth larvae are parasitized, both presence of a numerical herbivore refuge and parasitoid attack at high fruit and moth densities would be expected to stabilize long-term temporal dynamics of this simple food chain.     

Interactions of root and leaf herbivores on purple loosestrife (<Emphasis Type="Italic">Lythrum salicaria</Emphasis>)

Interspecific interactions of herbivores sharing a host plant may be important in structuring herbivore communities. We investigated host plant-mediated interactions of root (Hylobius transversovittatus) and leaf herbivores (Galerucella calmariensis), released to control purple loosestrife (Lythrum salicaria) in North America, in field and potted plant experiments. In the potted plant experiments, leaf herbivory by G. calmariensis reduced H. transversovittatus larval survival (but not larval development) but did not affect oviposition preference. Root herbivory by H. transversovittatus did not affect either G. calmariensis fitness or oviposition preference. In field cage experiments, we found no evidence of interspecific competition between root and leaf herbivores over a 4-year period. Our data suggest that large populations of leaf beetles can negatively affect root-feeding larvae when high intensity of leaf damage results in partial or complete death of belowground tissue. Such events may be rare occurrences (or affected by experimental venue) since field data differed from data obtained from potted plant experiments, particularly at high leaf beetle densities. Interspecific interactions between G. calmariensis and H. transversovittatus are possible and may negatively affect either species, but this is unlikely to occur unless heavy feeding damage results in partial or complete plant death.     

Egg cluster size variation in relation to the larval food abundance inLuehdorfia puziloi (Lepidoptera: Papilionidae)

Mean egg cluster size of Luehdorfia puziloi yessoensis varied among habitats. The mean egg cluster size tended to be large when abundance of the larval food leaves expressed as the fresh weight of leaves per unit area at a given habitat was high. Since this variation was observed among closely located study plots (butterflies can easily move between study plots), the egg cluster size variation among habitats is likely to be a result of flexible response by females to varying food abundance for larvae.     

Feeding damage by larvae of the mustard leaf beetle deters conspecific females from oviposition and feeding

Herbivorous insects may be informed about the presence of competitors on the same host plant by a variety of cues. These cues can derive from either the competitor itself or the damaged plant. In the mustard leaf beetle Phaedon cochleariae (Coleoptera, Chrysomelidae), adults are known to be deterred from feeding and oviposition by the exocrine glandular secretion of conspecific co-occurring larvae. We hypothesised that the exocrine larval secretion released by feeding larvae may adsorb to the surface of Chinese cabbage leaves, and thus, convey the information about their former or actual presence. Further experiments tested the influence of leaves damaged by conspecific larvae, mechanically damaged leaves, larval frass and regurgitant on the oviposition and feeding behaviour of P. cochleariae. Finally, the effect of previous conspecific herbivory on larval development and larval host selection was assessed. Our results show that (epi)chrysomelidial, the major component of the exocrine secretion from P. cochleariae larvae, was detectable by GC-MS in surface extracts from leaves upon which larvae had fed. However, leaves exposed to volatiles of the larval secretion were not avoided by female P. cochleariae for feeding or oviposition. Thus, we conclude that secretion volatiles did not adsorb in sufficient amounts on the leaf surface to display deterrent activity towards adults. By contrast, gravid females avoided to feed and lay their eggs on leaves damaged by second-instar larvae for three days when compared to undamaged leaves. Mechanical damage of leaves and treatment of artificially damaged leaves with larval frass or regurgitant did not affect oviposition and feeding of P. cochleariae. Since no adverse effects of previous herbivory on larval development were detected, we suggest that female P. cochleariae avoid Chinese cabbage leaves damaged by feeding larvae for other reasons than escape from competition or avoidance of direct negative effects that result from consuming induced plant material.