Enzymatic decomposition of elicitors of plant volatiles in Heliothis virescens and Helicoverpa zea

Feeding by larvae of Heliothis virescens induces cotton, corn and tobacco plants to release blends of volatile organic compounds that differ in constituent proportions from blends released when Helicoverpa zea larvae feed on the same plant species. The same elicitors (and analogs) of plant biosynthesis and release of volatiles, originally identified in oral secretions of Spodoptera exigua larvae, were also found in oral secretions of H. virescens and H. zea. However, relative amounts of these compounds, particularly N-(17-hydroxylinolenoyl)-L-glutamine (volicitin), 17-hydroxylinolenic acid, and N-linolenoyl-L-glutamine, varied among batches of oral secretions, more so in H. virescens than in H. zea. This variation was due to cleavage of the amide bond of the fatty acid-amino acid conjugates by an enzyme, or enzymes, originating in the midgut. The enzymatic activity in guts of H. virescens was significantly greater than that found in guts of H. zea. Furthermore, H. zea frass contains N-linolenoyl-L-glutamine in more than 0.1% wet weight, while this conjugate comprises only 0.003% wet weight in H. virescens frass. These results indicated that physiological differences between these two species affect the proportions of volicitin and its analogs in the caterpillars. Whether this causes different proportions of volatiles to be released by plants damaged by each caterpillar species is yet to be determined.     

Genetic variation and virulence of nucleopolyhedroviruses isolated worldwide from the heliothine pests Helicoverpa armigera, Helicoverpa zea, and Heliothis virescens

To assess the diversity and relationships of baculoviruses found in insects of the heliothine pest complex, a PCR-based method was used to classify 90 samples of nucleopolyhedrovirus (NPV; Baculoviridae: Alphabaculovirus) obtained worldwide from larvae of Heliothis virescens, Helicoverpa zea, and Helicoverpa armigera. Partial nucleotide sequencing and phylogenetic analysis of three highly conserved genes (lef-8, lef-9, and polh) indicated that 67 of these samples contained isolates of the H. zea-H. armigera single nucleopolyhedrovirus (Hz/HaSNPV) species group. Eighteen of the samples contained isolates of a multiple NPV from H. armigera, HearMNPV, and five of the samples contained isolates of Autographa californica MNPV (AcMNPV). Sequencing and analysis of an additional seven loci (orf5/orf5b, hr3-orf62, orf26, orf79, orf124/orf117a, orf42, and a part of the region between hr2 and hr3) in the Hz/HearSNPV isolates further classified these viruses into two groups of HearSNPV variants mostly from India and China and a third group of HzSNPV variants. Some of the samples contained isolates of more than one virus. In bioassays of a selection of isolates against H. zea, the commercially available Gemstar® isolate of HzSNPV killed larvae faster than most other Hz/HaSNPV and HearMNPV isolates. Gemstar® and two HearMNPV isolates exhibited significantly higher LC₅₀s than the Hz/HearSNPV isolates tested. This study expands significantly on what we know about the variation of heliothine NPV populations, provides novel information on the distinct groups in which these NPVs occur, and contributes to the knowledge required for improvement of heliothine baculoviruses as biological control agents.     

Central role of hemocytes in Autographa californica M nucleopolyhedrovirus pathogenesis in Heliothis virescens and Helicoverpa zea

Autographa californica M nucleopolyhedrovirus (AcMNPV) can infect and kill a wide range of larval lepidopteran hosts, but the dosage required to achieve mortal infection varies greatly. Using a reporter gene construct, we identified key differences between AcMNPV pathogenesis in Heliothis virescens and Helicoverpa zea, a fully permissive and a semipermissive host, respectively. Even though there was more than a 1,000-fold difference in the susceptibilities of these two species to mortal infection, there was no significant difference in their susceptibilities to primary infections in the midgut or secondary infections in the tracheal epidermis. Foci of infection within the tracheal epidermis of H. zea, however, were melanized and encapsulated by 48 h after oral inoculation, a host response not observed in H. virescens. Further, H. zea hemocytes, unlike those of H. virescens, were highly resistant to AcMNPV infection; reporter gene expression was observed only rarely even though virus was taken up readily, and nucleocapsids were transported to the nucleus. Collectively, these results demonstrated that hemocytes-by removing virus from the hemolymph instead of amplifying it and by participating in the encapsulation of infection foci-together with the host's melanization response, formed the basis of H. zea's resistance to fatal infection by AcMNPV.     

Heliothis virescens and Manduca sexta lipid rafts are involved in Cry1A toxin binding to the midgut epithelium and subsequent pore formation

Lipid rafts are characterized by their insolubility in nonionic detergents such as Triton X-100 at 4 degrees C. They have been studied in mammals, where they play critical roles in protein sorting and signal transduction. To understand the potential role of lipid rafts in lepidopteran insects, we isolated and analyzed the protein and lipid components of these lipid raft microdomains from the midgut epithelial membrane of Heliothis virescens and Manduca sexta. Like their mammalian counterparts, H. virescens and M. sexta lipid rafts are enriched in cholesterol, sphingolipids, and glycosylphosphatidylinositol-anchored proteins. In H. virescens and M. sexta, pretreatment of membranes with the cholesterol-depleting reagent saponin and methyl-beta-cyclodextrin differentially disrupted the formation of lipid rafts, indicating an important role for cholesterol in lepidopteran lipid rafts structure. We showed that several putative Bacillus thuringiensis Cry1A receptors, including the 120- and 170-kDa aminopeptidases from H. virescens and the 120-kDa aminopeptidase from M. sexta, were preferentially partitioned into lipid rafts. Additionally, the leucine aminopeptidase activity was enriched approximately 2-3-fold in these rafts compared with brush border membrane vesicles. We also demonstrated that Cry1A toxins were associated with lipid rafts, and that lipid raft integrity was essential for in vitro Cry1Ab pore forming activity. Our study strongly suggests that these microdomains might be involved in Cry1A toxin aggregation and pore formation.     

Structure and development of antennae in a moth,Manduca sexta

The antenna of the moth, Manduca sexta, comprises two small basal segments and a long (2 cm) flagellum, which is divided into nearly 80 annuli. The annuli bear cuticular scales and small sensory organs, sensilla. A trachea, a blood vessel, and two nerve trunks run through the lumen of the antenna and into the head. Sensilla are arranged in an orderly pattern that is repeated on each flagellar annulus. Each flagellum bears about 10⁵ sensilla, which contain about 2.5 × 10⁵ primary sensory neurons. Clumps of undifferentiated cells (imaginal disks), present in the larva, form pupal antennae during the larval-pupal molt. During the subsequent metamorphic development of the adult, cell divisions, changes in cell shape, and cellular differentiation transform pupal into adult antennae. Sensilla and scales arise and differentiate in the antenna during metamorphosis; regions in which sensilla and scales will arise can be recognized before overt differentiation occurs. All of the flagellar annuli develop synchronously. The dense innervation and neuronal simplicity of antennal flagella, as well as their synchronous development at a late and accessible stage in the animal's life cycle, suit them for studies of neuronal differentiation.     

Isolation and identification of paralytic peptides from hemolymph of the lepidopteran insects Manduca sexta, Spodoptera exigua, and Heliothis virescens

Seven paralytic peptides were isolated and identified from lepidopteran hemolymph. All of these peptides cause rapid, rigid paralysis when injected into Manduca sexta and some other lepidopteran larvae. Each peptide contains 23 amino acid residues including 2 cysteines and the carboxyl termini are acidic. Synthetic peptides in the disulfide or reduced forms, and as carboxyl-terminal acids or amides were equally paralytic. The most potent paralytic peptide, Mas PP I, has the following sequence: H-Glu-Asn-Phe-Ala-Gly-Gly-Cys-Ala-Thr-Gly-Tyr-Leu- Arg-Thr-Ala-Asp-Gly-Arg-Cys-Lys-Pro-Thr-Phe-OH. The two peptides from M. sexta hemolymph are remarkable in that they are autoparalytic (i.e. factors in collected hemolymph that are paralytic when injected into the same larvae).     

Survivorship of Helicoverpa zea and Heliothis virescens on cotton plant structures expressing a Bacillus thuringiensis vegetative insecticidal protein

A series of tests quantified bollworm, Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.), larval survival on plant structures of a nontransgenic cotton (Gossypium hirsutum L.), 'Coker 312', and two transgenic cottons expressing Vip3A protein or both Vip3A + CrylAb proteins (VipCot). Vegetative and reproductive structures including terminal leaves, flower bud (square) bracts, whole debracted squares, flower petals, flower anthers, and intact capsules (bolls) were harvested from plants in field plots. Each structure was infested with 2-d-old larvae from one of the two heliothine species. Larvae were allowed to feed for 96 h on fresh tissue. Survivorship at 96 h after infestation was significantly lower on all structures of Vip3A and VipCot cotton lines compared with similar structures of Coker 312. VipCot plant structures generally resulted in lower larval survivorship compared with similar structures of the Vip3A cotton line. H. zea survivorship ranged from 4 to 28% and from 1 to 18% on Vip3A and VipCot plant structures, respectively. H. virescens survivorship ranged from 10 to 43% and from 2 to 12% on Vip3A and VipCot plant structures, respectively. H. virescens survivorship was higher on VIP3A plant structures compared with that for H. zea on similar structures. These differences between species were not observed on plants from the cotton line expressing VipCot proteins. The results for these plant structures demonstrate that the combination of proteins expressed in VipCot cotton lines are more effective than Vip3A cotton lines against this heliothine complex.     

Developmental changes in the protein composition of Manduca sexta lipid droplets

The lipid droplets (LDs) are intracellular organelles mainly dedicated to the storage and provision of fatty acids. To accomplish these functions the LDs interact with other organelles and cytosolic proteins. In order to explore possible correlations between the physiological states of cells and the protein composition of LDs we have determined and compared the proteomic profiles of lipid droplets isolated from the fat bodies of 5th-instar larvae and adult Manduca sexta insects and from ovaries. These LD-rich tissues represent three clearly distinct metabolic states in regard to lipid metabolism: 1) Larval fat body synthesizes fatty acids (FA) and accumulates large amounts as triglyceride (TG); 2) Fat body from adult insects provides FA to support reproduction and flight; 3) Ovaries do not synthesize FA, but accumulate considerable amounts of TG in LDs. Major qualitative and semi-quantitative variations in the protein compositions of the LDs isolated from these three tissues were observed by MS/MS and partially validated by immuno-blotting. The differences observed included changes in the abundance of lipid droplet specific proteins, cytosolic proteins, mitochondrial proteins and also proteins associated with the machinery of protein synthesis. These results suggest that changes in the interaction of LDs with other organelles and cytosolic proteins are tightly related to the physiological state of cells. Herein, we summarize and compare the protein compositions of three subtypes of LDs and also describe for the first time the proteomic profile of LDs from an insect ovary. The compositions and compositional differences found among the LDs are discussed to provide a platform for future studies on the role of LDs, and their associated proteins, in cellular metabolism.     

Long-term seasonal abundance patterns of Helicoverpa zea and Heliothis virescens (Lepidoptera: Noctuidae) in the Texas High Plains

Bollworm, Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.), male adult (moth) activities were monitored between 1982 and 1995 by using sex pheromone traps in the Texas High Plains. Moths were monitored weekly from early March to mid-November near Lubbock and Halfway, two prominent cotton production areas in the Texas High Plains region. Based on trap captures, the bollworm-budworm complex consisted of approximately 98% bollworms and approximately 2% tobacco budworms. Seasonal activity patterns varied between location for bollworm but not for tobacco budworm. The 14-yr average (+/- SE) bollworm moth abundance (moths per trap per week) at Lubbock was significantly higher (226.5 +/- 10.4) compared with that at Halfway (153.7 +/- 8.1). Correlation analyses showed a significant positive relationship between moth abundance and average weekly temperatures, whereas a significant negative relationship was observed between moth abundance and average weekly wind velocity for both species. Analyses also showed a positive correlation between moth abundance and cumulative degree-days (> 0.0 degrees C) from 1 January. A strong positive relationship was observed between moth abundance and weekly average precipitation for both species. Average weekly abundances were positively correlated between adjacent months during most of the active cotton fruiting season (June-September). However, the relationship between populations that contributed to the overwintering generation and the following spring populations varied between species and study sites. Nevertheless, data from this study indicated that late-season moth catches could be indicative of the dynamics of the early-season moth catches the following year in the High Plains. The mean population abundance curve based on 14-yr averages showed two bollworm population peaks at Lubbock, but only one peak at Halfway. Separate degree-day-based models were developed to describe long-term seasonal abundance patterns of bollworm moths for the Lubbock and Halfway sites.     

Susceptibilities of Helicoverpa zea and Heliothis virescens (Lepidoptera: Noctuidae) populations to Cry1Ac insecticidal protein

Susceptibilities of bollworm, Helicoverpa zea (Boddie) and tobacco budworm, Heliothis virescens (F.) to Cry1Ac were measured via a diet-incorporated assay with MPV II at the University of Arkansas during 2002-2004. Lethal concentration-mortality (LC50) estimates of five laboratory, seven laboratory-cross, and 10 field populations of H. virescens varied 12-fold. Pooled susceptibilities of H. virescens across all laboratory and field populations varied five-fold. The LC50 estimates for H. virescens were higher than those reported by previous research before the introduction of transgenic crops. However, the ratio of susceptibility of laboratory and field populations was similar, suggesting no change in overall species susceptibility. Individual LC50 estimates of five laboratory, nine laboratory-cross, and 57 field populations of H. zea varied over 130-fold. Pooled susceptibilities across laboratory and field populations varied widely. Among the field populations, colonies from non-Bacillus thuringiensis (Bt) crops were generally more susceptible than those from Bt crops. Across the Bt crops expressing Cry protein, colonies from Bollgard (Monsanto Company) cotton had lower susceptibility to CrylAc than those from Bt corn and those from non-Bt crops.     

Brush border membrane binding properties of Bacillus thuringiensis Vip3A toxin to Heliothis virescens and Helicoverpa zea midguts

The binding properties of Vip3A, a new family of Bacillus thuringiensis insecticidal toxins, have been examined in the major cotton pests, Heliothis virescens and Helicoverpa zea. Vip3A bound specifically to brush border membrane vesicles (BBMV) prepared from both insect larval midguts. In order to examine the cross-resistance potential of Vip3A to the commercially available Cry1Ac and Cry2Ab2 toxins, the membrane binding site relationship among these toxins was investigated. Competition binding assays demonstrated that Vip3A does not inhibit the binding of either Cry1Ac or Cry2Ab2 and vice versa. BBMV protein blotting experiments showed that Vip3A does not bind to the known Cry1Ac receptors. These distinct binding properties and the unique protein sequence of Vip3A support its use as a novel insecticidal agent. This study indicates a very low cross-resistance potential between Vip3A and currently deployed Cry toxins and hence supports its use in an effective resistance management strategy in cotton.     

Acetylcholine and its metabolic enzymes in developing antennae of the moth, Manduca sexta.

Antennae of the moth, Manduca sexta, are thickly populated with sensory neurons, which send axons through antennal nerves to the brain. These neurons arise by cell divisions and differentiate synchronously during the 18 days of metamorphosis from pupa to adult. Biochemical studies support the hypothesis that antennal neurons use acetylcholine (ACh) as a neurotransmitter: (1) Antennae incubated with [¹⁴C]choline synthesize and store [¹⁴C]ACh; several other transmitter candidates do not accumulate detectably when appropriate radioactive precursors are supplied; (2) antennae and antennal nerves contain endogenous ACh; and (3) extracts of mature antennae contain choline acetyltransferase (ChAc) and acetylcholinesterase (AChE) with properties similar to those reported for the enzymes from other arthropods. Levels of ACh, ChAc, and AChE begin to increase in antennae soon after the sensory neurons are “born.” Levels rise exponentially for over a week as the neurons differentiate and then reach a plateau, at about the time the neurons reach morphological maturity, that is maintained into adulthood. In contrast, levels of carnitine acetyltransferase, cholinesterase, and soluble protein, presumably not confined to nervous tissue, change little during metamorphosis. Levels of ACh, ChAc, and AChE rise in an intracranial segment of antennal nerve at about the same time as in the antenna, indicating that axons can transport neurotransmitter machinery at an early stage in their development.     

2-Undecanone, a constituent of the glandular trichomes of Lycopersicon hirsutum f. glabratum: Effects on Heliothis zea and Manduca sexta growth and survival

The effects of 2-undecanone, a compound found in the glandular trichomes of the wild tomato, Lycopersicon hirsutum f. glabratum C. H. Mull, PI 134417, on the larvae of Heliothis zea (Boddie) and Manduca sexta (L.) were studied by rearing the larvae on artificial diets containing this chemical. 2-Undecanone increased larval mortality of H. zea in the first 48 h when combined with 2-tridecanone, but not alone, and caused deformity and mortality of H. zea pupae both alone and in combination with 2-tridecanone. 2-Undecanone had no effect on M. sexta larvae or pupae. Potential implications of these findings for insect pest management are discussed.

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Résumé Le 2-undécanone est une methyle cétone qui se trouve avec le 2-tridécanone dans les extrémités des poils glandulaires des feuilles de la tomate sauvage: Lycopersicon hirsutum f. glabratum C. H. Mull, PI 134417. Notre étude entreprendait à rechercher le rôle du 2-undécanone dans la resistance de cette plante à Heliothis zea et Manduca sexta.Les produits chimiques synthétiques s'étaient incorporés en diète artificièlle sur laquelle les insectes ont élevés. Le 2-undécanone a causé peu de mortalité des larves de H. zea sauf quand il soit combiné avec le 2-tridécanone, dans quel cas on trouve, dans les premiers 48 heures, une augmentation de mortalité, en comparaison au 2-tridécanone seul. Aussi le 2-undécanone a causé les difformités des nymphes de H. zea et la mortalité dans l'étage de nymphe, toutes les deux seul et en combinaison avec le 2-tridécanone. En contrast, le 2-undécanone n'a pas produit un effet sur les larves ou nymphes de M. sexta.L'élevage sélective des lignes de tomates de niveau plus élevé de 2-undécanone pourrait utile pour la lutte contre le H. zea. En combinaison avec des niveaux élevés du 2-tridécanone, c'est possible de reduire les populations nuisibles des larves. Il peut aussi réduire le nombre des lépidoptères adultes produit dans la récolte de tomate. Toutefois, il ne serait pas probablement de valeur dans la lutte contre le M. sexta.

     

Overwintering of Heliothis virescens (F.) and Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in cotton fields of northeast Mississippi

Following the 1995-2001 crop seasons, population densities of pupae of tobacco budworm, Heliothis virescens (F.), and corn earworm, Helicoverpa zea (Boddie), overwintering in cotton fields, Gossypium hirsutum L., in Monroe County, MS, were estimated by digging a total of 43,542 m-row. Densities of pupae varied greatly among years with the highest densities occurring in years with low rainfall in the late summer and early fall. The sex ratio of pupae was variable and significantly male-biased in some years. The total area-wide, tobacco budworm population emerging from all overwintering sites was estimated from catches in pheromone traps whose absolute efficiency is known. After the introduction of Bacillus thuringiensis Berliner (Bt)-transgenic cotton in 1996 but before a several-fold increase in use of herbicide resistant (HR)-transgenic cotton cultivars in 2001, local cotton fields accounted for <2% of the total overwintered tobacco budworm population. In the pretransgenic cotton production era, it is estimated cotton fields typically accounted for <10% of the overwintered tobacco budworm population. Driving surveys of the tillage status of cotton fields and pheromone trapping to determine the timing of adult emergence in the spring indicate that--until the 2000 crop season--postseason tillage destroyed most tobacco budworm and corn earworm pupae overwintering in cotton fields. Adoption of HR-transgenic cultivars has quintupled cotton field area planted no-till, but the contribution of cotton fields to overwintered tobacco budworm populations has remained low. Preemptive tillage of cotton fields to kill overwintering tobacco budworm pupae would not appreciably suppress in-season population densities of this pest. However, the absence of such tillage might increase the rate at which the tobacco budworm develops resistance to insecticides and counteradaptation to antibiotic host plant resistance traits including the Bt-transgenic trait.     

Neurons discovered in male Helicoverpa zea antennae that correlate with pheromone-mediated attraction and interspecific antagonism

Responses of single receptor neurons in the antennae of male Helicoverpa zea to sex pheromone components and to behavioral antagonists were recorded using a cut-sensillum extracellular recording technique. Three types of sensilla were identified from sampling 325 male-specific sensilla trichodea located at the lateral edge of antennomeres. The majority of these sensilla (71%) contained a receptor neuron tuned to the principal sex pheromone component (Z)-11-hexadecenal. A second sensillar type (10%) contained a receptor neuron that responded only to (Z)-9-tetradecenal. A third sensillar type (19%) contained a large-spiking neuron tuned to the secondary pheromone component (Z)-9-hexadecenal, but this neuron also could be stimulated to equivalent spike frequencies by the same emitted amounts of (Z)-9-tetradecenal. A smaller-spiking neuron in this sensillar type responded to two compounds known to act only as behavioral antagonists, (Z)-11-hexadecen-1-ol and (Z)-11-hexadecenyl acetate, and to (Z)-9-tetradecenal. Cross-adaptation studies confirmed the presence of one large- and one small-spiking neuron in the third sensillar type. Dose-response studies correlated to collected stimuli amounts showed that the large-spiking neuron in the third sensillar type was equally tuned to (Z)-9-hexadecenal and (Z)-9-tetradecenal, whereas the smaller-spiking neuron was far more sensitive to (Z)-11-hexadecen-1-ol and to (Z)-11-hexadecenyl acetate than to (Z)-9-tetradecenal. Accepted: 29 September 1997     

Locust adipokinetic hormone stimulates lipid mobilization in Manduca sexta

Adipokinetic hormone, a decapeptide isolated from the locust, stimulates mobilization of diacylglycerols from the locust fat body and loading of the lipid transport protein, lipophorin. Injection of the synthetic locust adipokinetic hormone into a sphinx moth, Manduca sexta, causes lipid loading of lipophorin. The lipophorin decreases in density from 1.11 to 1.06 g/ml, and a soluble protein from the hemolymph (apolipophorin III) associates with the lipophorin particle. Administration of intermediate doses of hormone indicates that lipophorin is converted directly to the low density form; no appreciable amounts of intermediate density particles are formed.     

Effects of allatotropin and allatostatin on in vitro production of juvenile hormones by the corpora allata of virgin females of the moths of Heliothis virescens and Manduca sexta

Retrocerebral complexes (RCs) were isolated from adult females of the moths Heliothis virescens and Manduca sexta. Different homologs of juvenile hormone (JH) produced by the isolated RCs were identified and amounts measured by capillary gas chromatography-chemical ionization (isobutane)-mass spectroscopy. Only JH I, II and III were identified. Incubation of RCs from both species in media containing acetate, but no propionate, induced production of approximately equal amounts of JH II and JH III, but the amount of JH I present was very low in all samples. Incubation of RCs with synthetic Manduca sexta allatotropin stimulated significant increases in production of all three homologs but increases in JH I and JH II were greater than those for JH III. The effect of allatotropin was mimicked by addition of propionate to the medium, which indicated that allatotropin increased supply of acetyl- and propionyl-CoA precursors. Incubation of tissue from H. virescens females during the first 24 h after eclosion with synthetic Manduca sexta allatostatin did not reduce production of JH. However, incubation of tissue from 3-day-old females with allatostatin significantly reduced production of JH. Similarly, incubation of tissue from H. virescens females during the first 24 h after eclosion with both allatotropin and allatostatin did not increase JH over the amount present in extracts from tissue incubated without the neuropeptides, indicating that allatostatin negated the action of allatotropin. Incubation of tissue from H. virescens females with allatostatin plus farnesol or JH III acid resulted in significant production of JH III, but neither JH I nor JH II was detected. These findings indicated that allatostatin acts prior to formation of the sesquiterpene alcohol precursors of JH.     

Dietary self-selection for vitamins and lipid by larvae of the corn earworm, Heliothis zea

Last instar larvae of the corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), require lipid and certain vitamins in their diet in order to complete larval development. When experimental larvae were offered two nutritionally incomplete diets, each lacking a different one of the requirements, they invariably ate from both diets, self-selecting a mixture that was nutritionally superior to either diet alone.

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Résumé Les chenilles de dernier stade d' H. zea (Boddie) (Lep.:Noctuidae) ont besoin de lipides et de certaines vitamines dans leur régime alimentaire, probablement parce qu'elles n'en contiennent pas assez provenant des stades précédents. Quand deux régimes incomplete ont été fournis aux chenilles (chacun privé différemment de l'un de ces consituants: lipide, chlorure de choline ou un ensemble de vitamines), elles ont consommé systématiquement des deux régimes et autosélectionné un aliment de qualité supèrieure à celle de chaque régime séparément. D'un autre côté, les chenilles témoins à qui on a offert deux régimes identiques et nutritionnellement complets, ont choisi apparemment leur aliment au hasard, et presque la moitié d'entre elles ont consommé exclusivement on presque exclusivement l'un des régimes, tandis que l'autre moitié a choise exclusivement or presque exclusivement l'autre.