The effects of host plant species and larval density on immune function in the polyphagous moth Spodoptera littoralis

Immune functions are costly, and immune investment is usually dependent on the individual''s condition and resource availability. For phytophagous insects, host plant quality has large effects on performance, for example growth and survival, and may also affect their immune function. Polyphagous insects often experience a large variation in quality among different host plant species, and their immune investment may thus vary depending on which host plant species they develop on. Larvae of the polyphagous moth Spodoptera littoralis have previously been found to exhibit density‐dependent prophylaxis as they invest more in certain immune responses in high population densities. In addition, the immune response of S. littoralis has been shown to depend on nutrient quality in experiments with artificial diet. Here, I studied the effects of natural host plant diet and larval density on a number of immune responses to understand how host plant species affects immune investment in generalist insects, and whether the density‐dependent prophylaxis could be mediated by host plant species. While host plant species in general did not mediate the density‐dependent immune expression, particular host plant species was found to increase larval investment in certain functions of the immune system. Interestingly, these results indicate that different host plants may provide a polyphagous species with protection against different kinds of antagonisms. This insight may contribute to our understanding of the relationship between preference and performance in generalists, as well as having applied consequences for sustainable pest management.     

Selection on offspring size varies within and among families in relation to host nutritional quality

Life history theory often assumes a positive relationship between offspring size and fitness, although the strength and form of this relationship is expected to vary with environmental conditions. In arthropods, surprisingly few studies have examined the influence of larval environment on the offspring size–fitness relation. In phytophagous insects, the few studies that have examined variation in larval host plants have found a negative correlation between host plant nutritional quality and the strength of selection favoring larger offspring size, suggesting that this pattern might be general. I present experimental evidence for such a relationship in a population of the moth Rothschildia lebeau feeding on its three primary host plant species. Unlike previous studies, I consider the effect of offspring size on growth and survival at two levels, both among families and among siblings within families. Neonate caterpillar mass had a significant effect on growth and survival. The effect on growth, however, was weak, resulted primarily from variation among families, and did not differ among host plant diets. The effect on survival was stronger and varied among host plant diets, among families, and within families on different host plants in a manner that was generally consistent with the hypothesized negative correlation between host plant nutritional quality and the strength of selection favoring larger offspring size. Overall, results suggest that the consequences of variation in offspring size for survival within and among families are host plant-dependent in this system.     

Comparative morphology of the prothoracic leg in heliconian butterflies: Tracing size allometry,podite fusions and losses in ontogeny and phylogeny

Prothoracic legs of heliconian butterflies (Nymphalidae, Heliconiinae, Heliconiini) are reduced in size compared to mesothoracic and metathoracic legs. They have no apparent function in males, but are used by females for drumming on host plants, a behavior related to oviposition site selection. Here, taking into account all recognized lineages of heliconian butterflies, we described their tarsi using optical and scanning electron microscopy and searched for podite fusions and losses, and analyzed allometry at the static, ontogenetic and phylogenetic levels. Female tarsi were similar, club-shaped, showing from four to five tarsomeres, each bearing sensilla chaetica and trichodea. Male tarsi were cylindrical, formed from five (early diverging lineages) to one (descendant lineages) either partially or totally fused tarsomeres, all deprived of sensilla. Pretarsi were reduced in both sexes, in some species being either vestigial or absent. Tarsal lengths were smaller for males in almost all species. An abrupt decrease in size was detected for the prothoracic legs during molting to the last larval instar at both histological and morphometric levels. In both sexes, most allometric coefficients found at the population level for the prothoracic legs were negative compared to the mesothoracic leg and also to wings. Prothoracic tarsi decreased proportionally in size over evolutionary time; the largest and smallest values being found for nodes of the oldest and youngest lineages, respectively. Our results demonstrate that evolution of the prothoracic leg in heliconian butterflies has been based on losses and fusions of podites, in association with negative size allometry at static, ontogenetic and phylogenetic levels. These processes have been more pronounced in males. Our study provided further support to the hypothesis that evolution of these leg structures is driven by females, by changing their use from walking to drumming during oviposition site selection. In males the leg would have been selected against due to absence of function and thus progressively reduced in size, in association with podites fusions and lost.     

Diversity of birch sawfly responses to seasonally atypical diets

Most insect herbivores are specialised on a particular plant taxon. To have a better understanding of host shift functions and consequences for insect herbivores, it is essential to gather more information on the effects of variation in host quality on specialists across species and environments. We examined the effects of seasonally atypical food on mortality, developmental time, and final body mass of six sawfly species (Hymenoptera: Symphyta) feeding on the foliage of mountain birch (Betula pubescens ssp. czerepanovii), whose pooled larval feeding periods form a gradient and cover the growing season. Insect phenology was manipulated so that the larvae of early-season species would feed on atypically mature leaves and mid- or late-season species would feed on atypically young leaves of their major host plant. Mortality increased dramatically for all species when the larval feeding schedule was advanced or delayed. This indicates a high degree of specialisation not only on a particular host but also to its phenological phases. The main cause of mortality on novel food was a rejection of the diet by the young larvae and their subsequent starvation. An interesting observation was that late-season species showed this response on nutritious young foliage. The effects of seasonally atypical diets on larval development and growth were species-specific and milder than the effects on mortality. Interestingly, for those individuals that accepted it, atypical food seemed to be most beneficial for species appearing at both ends of the seasonal gradient, which might be related to a wider exposure to variable food quality in natural conditions compared with other species. The diversity of responses to atypical food among closely related herbivore species with overlapping feeding periods on the same host plant is the most crucial finding of this study.     

Host plant induced variation in gut bacteria of Helicoverpa armigera

Helicoverpa are important polyphagous agricultural insect pests and they have a worldwide distribution. In this study, we report the bacterial community structure in the midgut of fifth instar larvae of Helicoverpa armigera, a species prevalent in the India, China, South Asia, South East Asia, Southern & Eastern Africa and Australia. Using culturable techniques, we isolated and identified members of Bacillus firmus, Bacillus niabense, Paenibacillus jamilae, Cellulomonas variformis, Acinetobacter schindleri, Micrococcus yunnanesis, Enterobacter sp., and Enterococcus cassiliflavus in insect samples collected from host plants grown in different parts of India. Besides these the presence of Sphingomonas, Ralstonia, Delftia, Paracoccus and Bacteriodetes was determined by culture independent molecular analysis. We found that Enterobacter and Enterococcus were universally present in all our Helicoverpa samples collected from different crops and in different parts of India. The bacterial diversity varied greatly among insects that were from different host plants than those from the same host plant of different locations. This result suggested that the type of host plant greatly influences the midgut bacterial diversity of H. armigera, more than the location of the host plant. On further analyzing the leaf from which the larva was collected, it was found that the H. armigera midgut bacterial community was similar to that of the leaf phyllosphere. This finding indicates that the bacterial flora of the larval midgut is influenced by the leaf surface bacterial community of the crop on which it feeds. Additionally, we found that laboratory made media or the artificial diet is a poor bacterial source for these insects compared to a natural diet of crop plant.     

Variation in susceptibility of Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) (Lepidoptera: Noctuidae) in Australia to two Bacillus thuringiensis toxins

Intra-specific variation in susceptibility of Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) in Australia to the Cry1Ac and Cry2Ab delta-endotoxins from Bacillus thuringiensis (Berliner) (Bt) was determined to establish a baseline for monitoring changes that might occur with the use of Bt cotton. Strains of H. armigera and H. punctigera were established from populations collected primarily from commercial farms throughout the Australian cotton belts. Strains were evaluated for susceptibility using two bioassay methods (surface treatment and diet incorporation) by measuring the dose response for mortality (LC50) and growth inhibition (IC50). The variation in LC50 among H. armigera (n=17 strains) and H. punctigera (n=12 strains) in response to Cry1Ac was 4.6- and 3.2-fold, respectively. The variation in LC50 among H. armigera (n=19 strains) and H. punctigera (n=12 strains) to Cry2Ab was 6.6- and 3.5-fold, respectively. The range of Cry1Ac induced growth inhibition from the 3rd to 4th instar in H. armigera (n=15 strains) was 3.6-fold and in H. punctigera (n=13 strains) was 2.6-fold, while the range of Cry2Ab induced growth inhibition from neonate to 3rd instar in H. armigera (n=13 strains) was 4.3-fold and in H. punctigera (n=12 strains) was 6.1-fold. Variation in susceptibility was also evaluated for two age classes (neonates and 3rd instars) in laboratory strains of H. armigera and H. punctigera. Neonates of H. punctigera had the same or higher sensitivity to Bt than 3rd instars. Neonates of H. armigera were more sensitive to Cry2Ab than 3rd instars, while being less sensitive to Cry1Ac than 3rd instars. Differences in the two methods of bioassay used affected relative sensitivity of species to Bt toxins, highlighting the need to standardize bioassay protocols.     

Effects of larval host plants on over-wintering preparedness and survival of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Laboratory colonies of cotton bollworm larvae, Helicoverpa armigera, kept at 20 degrees C under a photoperiod of L:D=10:14 were fed on five host plants (cotton, corn, kidney bean, tobacco and tomato) and an artificial diet (control) to determine the effects of larval host quality on survival and pupal over-wintering preparedness. A separate experiment showed that diapausing pupae weighed more and contained greater nutrient stores than did non-diapausing pupae. Diapausing pupae reared on different host plants showed significant differences in terms of over-wintering reserve storage, and degree of cold-hardiness (extent of low-molecular-weight substances and SCPs), and survivorship. The more nutrients the host plant had, the more the pupae weighed and the higher the levels of total lipids and glycogen. Body water content was also significantly affected by larval food quality. The mean pupal super-cooling capacities varied significantly from -16.7 to -18.9 degrees C according to host plants the larvae feed on, and these significantly related to water content, pupal weight, lipid and glycogen content, and the levels of glycerol. Levels of trehalose, glycerol, and inositol, which were mainly low-molecular-weight substances, showed no significant differences among different host plants, except for trehalose. Pupal mortality varied from 39.7% on corn to 3.3% on the artificial diet, which was significantly related to pupal weight, total lipid content, trehalose levels, and super-cooling points. These results suggest that larval food quality can affect survival and influence the over-wintering preparedness of the cotton bollworm.     

Diet factors responsible for the change of the glucose oxidase activity in labial salivary glands of Helicoverpa armigera

We investigated the change of the glucose oxidase (GOX) activity in labial salivary glands of Helicoverpa armigera larvae fed with the artificial diet or host plant tobacco and the major factors responsible for such a change. Throughout larval development, the labial salivary GOX activities in caterpillars reared on the artificial diet were remarkably higher than those fed with the plant. After fifth-instar plant-fed caterpillars were transferred to the artificial diet, their labial salivary GOX activity increased quickly, which was closely correlated with the time spent feeding on the artificial diet. The total sugar content of the artificial diet was 68 times higher than that of the tobacco leaves. We hypothesized that sugars and secondary metabolites are the possible causes of induction of GOX activity. When fifth-instar caterpillars were fed with tobacco leaves coated with glucose or sucrose, their labial salivary GOX activity was significantly higher than those fed with leaves without sugar coating. Following native PAGE, 1 single band of the labial salivary GOX was observed in all the caterpillars fed with different diets, implying that only the activity of the isoenzyme was changed in response to different diets. Furthermore, the labial salivary GOX activity was determined after caterpillars were fed with artificial diets containing chlorogenic acid, rutin, and quercetin. The results showed that all these phenolic compounds had no effect on the GOX activity. We conclude that sugar in diets was a major factor influencing the labial salivary GOX activity of the larvae. Arch. Insect Biochem. Physiol. 2008.     

Effects of class-specific,synthetic, and natural proteinase inhibitors on life-history traits of the cotton bollworm Helicoverpa armigera

Herbivorous insects have more difficulty obtaining proteins from their food than do predators and parasites. The scarcity of proteins in their diet requires herbivores to feed voraciously, thus heavily damaging their host plants. Plants respond to herbivory by producing defense compounds, which reduce insect growth, retard development, and increase mortality. Herbivores use both pre- and postdigestive response mechanisms to detect and avoid plant defense compounds. Proteinase inhibitors (PIs) are one example of plant compounds produced as a direct defense against herbivory. Many insects can adapt to PIs when these are incorporated into artificial diets. However, little is known about the effect of PIs on diet choice and feeding behavior. We monitored the diet choice, life-history traits, and gut proteinase activity of Helicoverpa armigera larvae using diets supplemented with synthetic and natural PIs. In choice experiments, both neonates and fourth-instar larvae preferred the control diet over PI-supplemented diets, to varying degrees. Larvae that fed on PI-supplemented diets weighed less than those that fed on the control diet and produced smaller pupae. Trypsin-specific PIs had a stronger effect on mean larval weight than did other PIs. A reduction of trypsin activity but not of chymotrypsin activity was observed in larvae fed on PI-supplemented diets. Therefore, behavioral avoidance of feeding on plant parts high in PIs could be an adaptation to minimize the impact of this plant's defensive strategy.     

Host selection and utilisation of Sonchus oleraceus (Asteraceae) by Helicoverpa armigera (Lepidoptera: Noctuidae): A genetic analysis

The cotton bollworm (Helicoverpa armigera) prefers the common sowthistle (Sonchus oleraceus L.) to cotton (Gossypium hirsutum L.), sorghum (Sorghum bicolor L.) and maize (Zea mays L.) for oviposition in the field in Australia. Using the common sowthistle and cotton as host plants, we carried out this study to evaluate genetic variation in both oviposition preference and larval growth and genetic correlation between maternal preference and larval performance. There was a significant genetic component of phenotypic variation in both characters, and the heritability of oviposition preference was estimated as 0.602. Helicoverpa armigera larvae survived slightly better and grew significantly faster on common sowthistle than on cotton, but genetic correlation between maternal preference and larval growth performance was not detectable. Instead, larval growth performance on the two hosts changed with families, which renders the interaction between family and host plant significant. As a result, the genetic correlation between mean values of larval growth across the two host species was not different from zero. These results are discussed in the context of the relationship between H. armigera and the common sowthistle and the polyphagous behaviour of this insect in general.     

Preference for high concentrations of plant pyrrolizidine alkaloids in the specialist arctiid moth Utetheisa ornatrix depends on previous experience

Secondary metabolites are one the most pervasive defensive mechanisms in plants. Many specialist herbivores have evolved adaptations to overcome these defensive compounds. Some herbivores can even take advantage of these compounds by sequestering them for protection and/or mate attraction. One of the most studied specialist insects that sequesters secondary metabolites is the arctiid moth Utetheisa ornatrix. This species sequesters pyrrolizidine alkaloids (PAs) from its host plant, the legume Crotalaria spp. The sequestered PAs are used as a predator repellent and as a mating pheromone. We used this species to test larval preference for different concentrations of PAs. We purified PAs from plant material and added them at different concentrations to an artificial diet. Larvae of U. ornatrix previously feeding on low and high PA concentration artificial diets were allowed to choose between two new artificial diets with different PA concentrations. The amount of PAs sequestered and larval preference were dependent on their previous exposure to low or high PA content in the diet. Larvae that were pretreated with a low PA diet significantly consumed more diet with the high PA concentration, while larvae that were pretreated with a high PA diet showed no discrimination between future feeding of different PA concentration diets. We discuss our results using mechanistic and evolutionary approaches. Finally, we discuss how these results have important implications on the evolution of plant herbivore interactions and how specialist herbivores may decrease the levels of chemical defenses on plant populations.     

Quantitative genetics of preference and performance on chickpeas in the noctuid moth, Helicoverpa armigera

If a novel, resistant host-plant genotype arises in the environment, insect populations utilising that host must be able to overcome that resistance in order that they can maintain their ability to feed on that host. The ability to evolve resistance to host-plant defences depends upon additive genetic variation in larval performance and adult host-choice preference. To investigate the potential of a generalist herbivore to respond to a novel resistant host, we estimated the heritability of larval performance in the noctuid moth, Helicoverpa armigera, on a resistant and a susceptible variety of the chickpea, Cicer arietinum, at two different life stages. Heritability estimates were higher for neonates than for third-instar larvae, suggesting that their ability to establish on plants could be key to the evolution of resistance in this species; however, further information regarding the nature of selection in the field would be required to confirm this prediction. There was no genetic correlation between larval performance and oviposition preference, indicating that female moths do not choose the most suitable plant for their offspring. We also found significant genotype by environment interactions for neonates (but not third-instar larvae), suggesting that the larval response to different plant genotypes is stage-specific in this species.     

Responses of midgut amylases of Helicoverpa armigera to feeding on various host plants

Midgut digestive amylases and proteinases of Helicoverpa armigera, a polyphagous and devastating insect pest of economic importance have been studied. We also identified the potential of a sorghum amylase inhibitor against H. armigera midgut amylase. Amylase activities were detected in all the larval instars, pupae, moths and eggs; early instars had lower amylase levels which steadily increased up to the sixth larval instar. Qualitative and quantitative differences in midgut amylases of H. armigera upon feeding on natural and artificial diets were evident. Natural diets were categorized as one or more members of legumes, vegetables, flowers and cereals belonging to different plant families. Amylase activity and isoform patterns varied depending on host plant and/or artificial diet. Artificial diet-fed H. armigera larvae had comparatively high amylase activity and several unique amylase isoforms. Correlation of amylase and proteinase activities of H. armigera with the protein and carbohydrate content of various diets suggested that H. armigera regulates the levels of these digestive enzymes in response to macromolecular composition of the diet. These adjustments in the digestive enzymes of H. armigera may be to obtain better nourishment from the diet and avoid toxicity due to nutritional imbalance. H. armigera, a generalist feeder experiences a great degree of nutritional heterogeneity in its diet. An investigation of the differences in enzyme levels in response to macronutrient balance and imbalance highlight their importance in insect nutrition.     

Differential responses of midgut soluble aminopeptidases of Helicoverpa armigera to feeding on various host and non-host plant diets

Differential responses of midgut soluble aminopeptidases were studied in Helicoverpa armigera larvae fed on various host (chickpea and pigeon pea) and non-host (bitter gourd and chili) plant diets. Larval growth was significantly reduced by non-host plant diets. Although the serine proteinase activities were inhibited, aminopeptidase activities were significantly increased in the larvae fed on non-host plant diets. Results were qualitatively and quantitatively confirmed with in vivo and in vitro analyses. It was noted that aminopeptidases had given more preference to ApNA than LpNA on non-host plant diets and vice versa on host plant diets. However, optimum pH for aminopeptidase activity (around pH 7.0–8.0) and susceptibility to inhibitors was similar in the larvae fed on host as well as non-host plant diets. These results suggest that H. armigera regulates digestive enzyme levels to obtain better nourishment from the diet and avoid toxicity due to nutritional imbalance. A detailed biochemical and molecular analysis of gut aminopeptidases upon exposure of the insect to a particular diet will highlight their specific roles.     

Development, fecundity and survival of the herbivore Lymantria dispar and the number of plant species in its diet

ABSTRACT.

• 1 Larval gypsy moth Lymantria dispar (L.) mortality depends upon the number and type of plant species consumed as well as the sequence in which they are consumed.
• 2 When a two-species diet is composed of a favourable and an unfavourable species, larval mortality is higher on the two-species diet than on the diet of the favourable species alone.
• 3 When a two species diet is composed of a favourable and unfavourable coniferous species, larval mortality is higher on the single conifer species diet than on the two-species diet.
• 4 Two-species diets, in which one species is a conifer, produce individuals with a greater fecundity than diets of either species alone.
• 5 The influence of diets composed of two favourable species, on development, size and fecundity, depends both on the relative quality of each of the two plant species and which of the two is consumed by older instars.

     

棉花单宁-黄酮类化合物对棉铃虫的抗性潜力

陆地棉棉叶甲醇提取物包含了棉花的大部分单宁-黄酮类化合物。这些化合物对棉花多种病虫害具有抗性作用。将这些化合物定量加入人工饲料中饲养棉铃虫龄幼虫5d,结果表明,培儿茶素、缩合单宁、芸香苷和异槲皮苷在饲料中的浓度增加均与幼虫体重生长呈显著负相关,ED50分别为0．81％,0．49％,0．57％和0．83％;儿茶素则不存在这种关系;用含0．8％的浓度桔儿茶素、缩合单宁,芸香苷和异槲皮苷的饲料测试棉铃虫,发现随取食量的增加,相对生长率的增加显著低于对照(不含次牛物质),即这些物质属于慢毒剂,而儿茶素仅有阻食作用。     

Effect of 13 single and eight mixed host plant diets on survival, post-embryonic development and morphology of variegated grasshopper in laboratory

Zonocerus variegatus (Orthoptera: Pyrgomorphidae) is known as an agricultural pest in West and Central Africa. In this study, the effects of 13 single and eight mixed host plant diets on the survival, post-embryonic development and morphology of Z. variegatus in the laboratory were investigated. In each cage, 20 one-day larvae were provided with these diets and their survival monitored every two days, from August 2000 to September 2002, until all individuals died. Results showed that the number of larval stages varied from six to eight according to the diet. Six larval stages were most frequent. Development to the adult stage (complete development) was only noted with 52% of diets. All the mixed host plant diets induced complete development of Z. variegatus except that of Cajanus cajan + Synedrella nodiflora + Chromolaena odorata . Complete development was observed with four single host plant diets: Lablab purpurea , C. cajan , Manihot esculenta and S. nodiflora . Compared to leguminous species and Asteraceae, M. esculenta (Euphorbiaceae) was the species that resulted in the highest level of survival and development of Z. variegatus . Chromolaena odorata and S. nodiflora (Asteraceae) induced late appearance of the different Z. variegatus nymphal instars and the appearance time was shorter on legumes. The supernumerary stage 7 has the same color as the larva in stages 1–6, but this larva was significantly larger than stage 6 and smaller than the adult stage. These results indicate that legumes for short fallows affected the survival and post-embryonic development of Z . variegatus in the laboratory.     

Effects of host switching on gypsy moth (Lymantria dispar (L.)) under field conditions

Effects of various single and two species diets on the performance of gypsy moth (Lymantria dispar (L.)) were studied when this insect was reared from hatch to population on intact host trees in the field. The tree species used for this study were red oak (Quercus rubra L.), white oak (Q. alba L.), bigtooth aspen (Populus grandidentata Michaux), and trembling aspen (P. tremuloides Michaux). These are commonly available host trees in the Lake States region. The study spanned two years and was performed at two different field sites in central Michigan. Conclusions drawn from this study include: (1) Large differences in gypsy moth growth and survival can occur even among diet sequences composed of favorable host species. (2) Larvae that spent their first two weeks feeding on red oak performed better during this time period than larvae on all other host species in terms of mean weight, mean relative growth rate (RGR), and mean level of larval development, while larvae on a first host of bigtooth aspen were ranked lowest in terms of mean weight, RGR, and level of larval development. (3) Combination diets do not seem to be inherently better or worse than diets composed of only a single species; rather, insect performance was affected by the types of host species eaten and the time during larval development that these host species were consumed instead of whether larvae ate single species diets or mixed species diets. (4) In diets composed of two host species, measures of gypsy moth performance are affected to different extents in the latter part of the season by the two different hosts; larval weights and development rates show continued effects of the first host fed upon while RGRs, mortality, and pupal weights are affected strongly by the second host type eaten. (5) Of the diets investigated in this study, early feeding on red oak followed by later feeding on an aspen, particularly trembling aspen, is most beneficial to insects in terms of attaining high levels of performance throughout their lives.     

A tree in the eyes of a moth – temporal variation in oak leaf quality and leaf-miner performance

When examined at any moment in time, different parts of an individual oak tree exhibit almost as large differences in quality as different trees. But how consistent are such patterns in time? In this paper, we use intraclass correlations to assess the temporal consistency of host plant quality at several spatial scales. As measures of quality, we use both individual chemical attributes (phenolic contents) and the overall performance (larval survival) of the host‐specific leaf‐miner Tischeria ekebladella. Concentrations of 24 phenolic compounds were monitored on seven trees throughout a season. Variation in mine initiation and larval survival rates was assessed for individuals transplanted to another set of trees early versus later in the season, while year‐to‐year variation in larval survival was studied through stratified surveys of wild individuals during three years. At all time scales considered, measures of host quality were moderately consistent: a tree favourable in quality at one point in time often remained so, but there was abundant variation around this relationship (ρ=0.4–0.6). One hierarchical level deviated from this general pattern: on individual branches, larval survival rates varied randomly among years (ρ=0). Our study suggests that the quality of trees, and in particular of smaller units within trees, may be difficult to predict both in space and in time. To account for this, insects might benefit from adopting a bet‐hedging strategy when selecting resources.     

Geographic and parental influences on diapause by a polyphagous insect herbivore

1 Facultative diapause permits insects to initiate an additional generation when conditions are favourable, or to enter diapause when they are not. Although the principle environmental cues for diapause induction are often temperature and photoperiod, we demonstrated recently that the quality of host plant consumed by the larvae of Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) influences the proportion of larvae that enter diapause and therefore voltinism. 2 Previous work has also suggested that non‐Mendelian parental effects influence diapause by C. rosaceana larvae, but the mechanism was not established. Here, we report further evidence for parental effects on diapause and examine whether parental diet influences diapause induction. 3 We collected larvae of C. rosaceana from six sites at three latitudes in the Province of Québec. There was an increase in the proportion of larvae entering diapause with increasing latitude. Rearing larvae under identical conditions on artificial diet for two generations significantly reduced variation in diapause among populations within a given latitude, and supported the existence of parental effects that influence offspring diapause. 4 Experiments with different host plants and high‐ vs. low‐quality artificial diets provided no evidence that the parental effects on offspring diapause were based on the quality of food consumed by parents. Diapause in C. rosaceana appears influenced by a hierarchy of cues, including temperature, photoperiod, current larval diet and parental environment.