Airborne differences in odors emitted byRattus norvegicus in response to reward and nonreward

To test the hypothesis that rats (Rattus norvegicus) emit airborne, differential odors in response to reward and nonreward, donor rats received random sequences of rewarded and nonrewarded placements in small compartments and an airstream transported odors from these compartments to test rats in a separate chamber. When donors remained in the compartments during, or were removed just prior to, air transport, test rats utilized transported odors as discriminative cues signaling their own reward and nonreward for a lever-press response. When the airstream was passed through a clean compartment containing paper flooring extracted from donor compartments, test rats were not able to discriminate. Test trials to assess for control by food odors suggest that donor-produced odors, rather than food odors per se, provided the discriminative signals for test rats. Results confirm the existence of somewhat volatile, although apparently stable, odors emitted in response to reward and nonreward, and implicate a differential in amount and/or type of odor produced by donors to these two events as the source of discriminative control.     

Scent,sex, and the self-calibrating rat

We propose that one mechanism whereby male rats,Rattus norvegicus, might gauge the reproductive condition of a female is by calibrating a stable odor with an odor that fluctuates through her reproductive cycle. We provide behavioral and histological evidence in support of such a self-calibration model. Male rats sniffed frequently at various body zones of females, and the proportion of sniffs deployed to each zone varied with the females' reproductive condition and relatedness. The females' haunches received more sniffs than any other part of their bodies, irrespective of their relatedness or reproductive condition. Furthermore, males tended to sniff the haunch after sniffing the forequarters, as part of a sequence of sniffing along a female from forequarters to hindquarters. Histology of the skin sebaceous glands indicated that the secretory activity of glands in the haunch, but not those in the forequarters, changed during estrus. Therefore, male rats had the opportunity to judge a female's reproductive status by calibrating the odor of her haunch against that of her forequarters. Self-calibration could represent a means of accommodating differences in odor within individuals.     

Responses of Wild Norway Rats (Rattus norvegicus) to Predator Odors

If rats could be shown to avoid the odors of predators, then conservation managers could manipulate this behavior to exclude rats from important conservation sites. We evaluated the ability of six predator odors to elicit avoidance responses by wild-caught Norway rats (Rattus norvegicus) from two New Zealand populations (Kapiti Island and North Island). Kapiti Island is free of mammalian predators, while the North Island has established populations of felids, canids, and mustelids. Three of the predator odors were real and three were synthesized volatile ingredients of real animal feces or urine. We compared the rats' responses to predator odors with their responses to three natural herbivore odors. We used a Y maze, and rats were offered the choice of an odor in one arm of the maze and distilled water in the other arm. Each choice arm was ducted at the entrance to remove air and the odor. We recorded: (1) the time until the rat left the first arm of the maze, (2) the time until the rat visited each arm, (3) the number of visits to each arm, (4) the amount of time spent in each arm, and (5) a total activity score for each rat. Kapiti rats showed an aversion to five of the six predator odors, despite never having encountered them before. Kapiti rats visited herbivore odors more often than carnivore odors and were less active in the presence of carnivore odors than they were when tested with herbivore odors. In addition, Kapiti rats approached some herbivore odors more quickly than they approached carnivore odors. North Island rats appeared to avoid cat urine, but despite being predator experienced, did not show a consistent aversion to the carnivore odors we tested. Both samples of rats, but particularly the North Island group, showed high individual variation. We conclude that predator odors are unlikely to be an effective management tool for all populations of this species of rat because of this high individual variability and the likelihood that each island population will differ in its responses to a given odor.     

Laboratory Evaluation of Predator Odors for Eliciting an Avoidance Response in Roof Rats (Rattus rattus)

We evaluated eight synthetic predator odors and mongoose (Herpestes auropunctatus) feces for eliciting avoidance responses and/or reduced feeding by wild captured Hawaiian roof rats (Rattus rattus). In a bioassay arena, we recorded: (1) time until each rat entered the arena, (2) time elapsed until first eating bout, (3) time spent in each half of the arena, (4) number of eating bouts, and (5) consumption. Rats displayed a response to the predator odors in terms of increased elapsed time before initial arena entry and initial eating bout, a lower number of eating bouts, and less food consumption than in the respective control groups. The odor that produced the greatest differences in response relative to the control group was 3,3-dimethyl-1,2-dithiolane [from red fox (Vulpes vulpes) feces and mustelid anal scent gland]. Mongoose fecal odor produced different responses in four of the five variables measured while (E,Z)-2,4,5-trimethyl-³-thiazoIine (red fox feces) and 4-mercapto-4-methylpentan-2-one (red fox urine and feces) odors were different from the control group in three of the five variables measured. These laboratory responses suggest that wild Hawaiian roof rats avoid predator odors.     

Inheritance Of Resistance to Mammalian Herbivores and of Plant Defensive Chemistry in an <Emphasis Type="Italic">Eucalyptus</Emphasis> Species

Hybridization in plants provides an opportunity to investigate the patterns of inheritance of hybrid resistance to herbivores, and of the plant mechanisms conferring this resistance such as plant secondary metabolites. We investigated how inter-race differences in resistance of Eucalyptus globulus to a generalist mammalian herbivore, Trichosurus vulpecula, are inherited in their F₁ hybrids. We assessed browsing damage of 3-year-old trees in a common environment field trial on four hybrid types of known progeny. The progeny were artificial intra-race crosses and reciprocal inter-race F₁ hybrids of two geographically distinct populations (races) of E. globulus north-eastern Tasmania and south-eastern Tasmania. Populations of trees from north-eastern Tasmania are relatively susceptible to browsing by T. vulpecula, while populations from south-eastern Tasmania are more resistant. We assessed the preferences of these trees in a series of paired feeding trials with captive animals to test the field trial results and also investigated the patterns of inheritance of plant secondary metabolites. Our results demonstrated that the phenotypic expression of resistance of the inter-race F₁ hybrids supported the additive pattern of inheritance, as these hybrids were intermediate in resistance compared to the pure parental hybrids. The expression of plant secondary metabolites in the F₁ hybrids varied among major groups of individual compounds. The most common pattern supported was dominance towards one of the parental types. Together, condensed tannins and essential oils appeared to explain the observed patterns of resistance among the four hybrid types. While both chemical groups were inherited in a dominant manner in the inter-race F₁ hybrids, the direction of dominance was opposite. Their combined concentration, however, was inherited in an additive manner, consistent with the phenotypic differences in browsing.     

Induction of Plant Volatiles by Herbivores with Different Feeding Habits and the Effects of Induced Defenses on Host-Plant Selection by Thrips

Induced plant responses to attack by chewing insects have been intensively studied, but little is known about plant responses to nonchewing insects or to attack by multiple herbivores with different feeding habits. We examined volatile emissions by tobacco, Nicotiana tabacum, in response to feeding by the piercing–sucking insect western flower thrips (WFT), Frankliniella occidentalis, the chewing herbivore Heliothis virescens, and both herbivores simultaneously. In addition, we examined the effects of herbivore-induced plant defenses on host-plant selection by WFT. Plants responded to thrips feeding by consistently releasing five compounds. Simultaneous feeding by WFT and H. virescens elicited the same 11 compounds emitted in response to caterpillar feeding alone; however, two compounds, α-humulene and caryophyllene oxide, were produced in greater amounts in response to simultaneous herbivory. In choice tests, thrips consistently preferred uninduced plants over all other treatments and preferred plants damaged by caterpillars and those treated with caterpillar saliva over those treated with caterpillar regurgitant. The results are consistent with a previous finding that caterpillar regurgitant induces the release of significantly more volatile nicotine than plants damaged by caterpillars or plants treated with caterpillar saliva. A repellent effect of nicotine on WFT was confirmed by encircling unwounded plants with septa releasing volatile nicotine. Our results provide the first direct evidence that thrips feeding induces volatile responses and indicates that simultaneous herbivory by insects with different feeding habits can alter volatile emissions. In addition, the findings demonstrate that induced plant responses influence host-plant selection by WFT and suggest that the induction of volatile nicotine may play a role in this process.     

Effect of Previous Exposure to Hydroxamic Acids in Probing Behavior of Aphid Sitobion fragariae on Wheat Seedlings

We hypothesized that aphids after previous exposure to hydroxamic acids (Hx), a family of secondary plant compounds deleterious to aphids, are able to reduce their subsequent exposure to them. This hypothesis was tested by evaluating the time to produce salivation into a sieve element (SSE) by the aphid Sitobion fragariae on seedlings of two wheat cultivars of Triticum aestivum differing in their concentration of Hx. The total time to produce a first SSE was significantly longer in the high-Hx cultivar; however, the subsequent, second SSE (first SSE after interruption of probing) in this cultivar was significantly reduced, reaching the level observed in the low-Hx plants. Therefore, a strategy to reduce the exposure to secondary compounds was observed only in the second SSE in high-Hx plants. When the experimental plant was replaced by a new unattacked plant after the first SSE, aphids did not change the behavior described, thus excluding an aphid-induced plant susceptibility. The number of cell punctures and accumulated duration was not affected by previous exposure to Hx, either in low or high Hx cultivars. Total time and pathway time but not cell punctures, seem to be the variables affected by previous exposure to Hx.     

Reproduction and Urine Marking in Laboratory Groups of Female Common Voles Microtus arvalis

In laboratory groups of common voles, Microtus arvalis, consisting of one mother, two of her daughters and one male, mainly the mother reproduced. The three females spent most of the time in close body contact. By using a modified method of coloring the urine of the three females by nonmetabolizable, nontoxic dyes, we found that mothers display a higher urine marking intensity than their daughters, and urine marks from the mother were distributed more frequently than those from the daughters. The results suggest that both pheromonal and behavioral mechanisms are involved in the regulation of reproduction in matriarchal groups of common voles.     

Intraspecific Variation in Plant Defense Alters Effects of Root Herbivores on Leaf Chemistry and Aboveground Herbivore Damage

Root herbivores can indirectly affect aboveground herbivores by altering the food quality of the plant. However, it is largely unknown whether plant genotypes differ in their response to root herbivores, leading to variable defensive phenotypes. In this study, we investigated whether root-feeding insect larvae (Agriotes sp. larvae, wireworms) induce different responses in Plantago lanceolata plants from lines selected for low and high levels of iridoid glycosides (IG). In the absence of wireworms, plants of the “high-IG line” contained approximately twofold higher levels of total IG and threefold higher levels of catalpol (one of the IG) in leaves than plants from the “low-IG line,” whereas both lines had similar levels of IG in roots. In response to wireworms, roots of plants from both lines showed increased concentrations of catalpol. Leaves of “low-IG line” plants increased catalpol concentrations in response to wireworms, whereas catalpol concentrations of leaves of “high-IG line” plants decreased. In contrast, glucose concentrations in roots of “low-IG” plants decreased, while they increased in “high-IG” plants after feeding by wireworms. The leaf volatile profile differed between the lines, but was not affected by root herbivores. In the field, leaf damage by herbivores was higher in wireworm-induced compared to noninduced “low-IG” plants and lower in wireworm-induced compared to noninduced “high-IG” plants, despite induction of catalpol in leaves of the “low-IG” plants and reduction in “high-IG” plants. This pattern might arise if damage is caused mainly by specialist herbivores for which catalpol may act as feeding stimulant rather than as deterrent. The present study documents for the first time that intraspecific variation in plant defense affects the outcome of plant-mediated interactions between root and shoot herbivores.     

The Defensive Role of Volatile Emission and Extrafloral Nectar Secretion for Lima Bean in Nature

Lima bean (Phaseolus lunatus) features two indirect anti-herbivore defenses—emission of volatile organic compounds (VOCs) and secretion of extrafloral nectar (EFN)—which are both inducible upon herbivore damage. In a previous field study, Lima bean benefited from the simultaneous induction of the two defenses, yet it remained unclear whether both had contributed to plant protection. Our experimental approach aimed at studying the defensive role of both indirect defenses simultaneously. Tendrils were sprayed with jasmonic acid (JA) to induce both defenses, and performance was compared to that of others that were treated with a synthetic blend of either EFN or VOCs. Confirming earlier results, JA treatment and application of the VOC mixture induced EFN secretion in treated tendrils in quantitatively similar amounts. The composition of the applied synthetic blend of EFN was adjusted to match the concentration of EFN secreted from JA- and VOC-treated tendrils. Repeated application of either enhanced the performance of several fitness-relevant plant parameters such as growth rate and flower production. Tendrils treated with JA showed a similar trend, yet some fitness-related parameters responded less to this treatment. This suggests a minor importance of any putative JA-dependent direct defense traits or higher costs of JA-elicited responses as compared to VOCS and EFN, as otherwise JA-treated tendrils should have outperformed VOC- and EFN-treated tendrils. Moreover, the beneficial effect of applying synthetic EFN alone equaled or exceeded that of VOCs and JA. Ants were by far the dominant group among the arthropods that was attracted to JA-, VOC-, or EFN-treated tendrils. The results suggest that EFN plays a more important role as an indirect defense of lima bean than VOCs or any other JA-responsive trait. Electronic supplementary material The online version of this article doi: contains supplementary material, which is available to authorized users.     

Structure-activity relationship of stress-inducing odorants in the rat

The stress for 12 sulfur-containing synthetized volatiles was evaluated in male Wistar rats and compared to that for fox-dropping extract concentrate. Stress behavior was analyzed by quantifying various stress responses in a standard open field and measuring the increase in plasma corticosterone concentration. Nine compounds induced stress—a dihydrothiazole, two cyclic polysulfides, five mercaptoketones, and a mercaptan. For the mercaptoketones, the following structure-activity relationships were observed. Size can vary considerably; the mercapto group can be either alpha or beta and either secondary or tertiary. The keto group is not essential, since a structurally related mercaptan remains active. The mercapto group is essential for activity in mercaptoketones, since conversion to a methyl sulfide resulted in a neutral response. This type of odorant could function as an allomone and may have potential in rat control as an area repellent.     

Consumption of c9,t11-18:2 or t10,c12-18:2 enriched dietary supplements does not influence milk macronutrients in healthy, lactating women

Substantial research suggests that the t10,c12–18:2, but not the c9,t11–18:2, isomer of conjugated linoleic acid (CLA) reduces milk fat synthesis in lactating bovine and rodent species. Because fat is the major energy-yielding component in human milk, we were interested in whether this is true for women as well. Thus, the effects of c9,t11–18:2 and t10,c12–18:2 on milk fat were examined in breast-feeding women (n = 12) in a double-blind, placebo-controlled, crossover study with latin-square design. The study was divided into six periods: baseline (3 days), three intervention periods (5 days each), and two washout periods (9 days each). During each intervention period, women consumed 750 mg/day of a supplement containing predominantly c9,t11–18:2, t10,c12–18:2, or 18:1 (olive oil placebo). Milk was collected by complete breast expression on the final day of each period. Infant milk consumption was estimated by 24 h weighing on the penultimate day of each intervention and washout period, and maternal adiposity (% body fat) was determined at baseline using dual energy X-ray absorptiometry. Milk c9,t11–18:2 and t10,c12–18:2 concentrations were greater (P < 0.05) during the corresponding CLA treatment periods as compared to the placebo period, providing strong evidence of subject compliance. Both CLA isomers were transferred into milk fat at relatively high efficiency; average transfer efficiency was estimated to be 23.3%. Compared to the placebo treatment, milk fat content was not reduced during either CLA treatment. Data indicate that body fatness did not modify any putative effect of isomeric CLA consumption on milk fat concentration. The evidence from this study suggests that the sensitivity of lactating women’s mammary tissue to an anti-lipogenic effect of the t10,c12–18:2 isoform of CLA may be less than previously hypothesized.     

Effect of Wind Speed on the Pheromone-Mediated Behavior of Sexual Morphs of the Potato Aphid, Macrosiphum euphorbiae (Thomas) Under Laboratory and Field Conditions

The effect of wind on the potato aphid, Macrosiphum euphorbiae, male responsiveness to the sex pheromone, and on the calling behavior of virgin oviparae, was studied under constant wind speeds in the laboratory and in the field. A significant proportion of females called at wind speeds up to 4 m/sec, whereas male flight behavior in clean air was inhibited at velocities > 2 m/sec. However, males continued to walk over the range of wind speeds at which females called. Under constant wind velocities in a wind tunnel, males downwind of calling females oriented on the upwind edge of the release stand, and fewer individuals took flight at low constant wind speeds than in a clean air plume. In all cases, whether calling females were present or not, the males that took flight moved downwind. However, when a bridge was available, a significant proportion of males walked upwind to the pheromone source. The same orientation and walking behaviors were observed when males were placed downwind of calling females under variable wind conditions in the field. However, contrary to the laboratory results, 30% of the males tested flew upwind and landed on the source. A more detailed examination found that males orienting toward a source would walk if wind speeds were high but initiated flight in an “upwind” direction if there was a lull in wind velocity. These findings suggest that for the potato aphid, and probably for many other insect species with weak flight capacity, walking behavior is a significant component of pheromone-mediated mate location. This would permit males to continue foraging for calling females in the vicinity when wind velocities inhibit flight.     

Foraging Behavior of Anastrepha Ludens, A. obliqua, and A. serpentina in Response to Feces Extracts Containing Host Marking Pheromone

Following oviposition, females of many Tephritid flies deposit host marking pheromones (HMPs) to indicate that the host fruit has been occupied. We describe the foraging behavior of these three economically important species (Anastrepha ludens and A. obliqua from the fraterculus species group and A. serpentina from the serpentina species group) when they encounter an artificial fruit (green agar spheres wrapped in Parafilm) marked with intra- and interspecific feces extracts that contain, among other substances, host marking pheromone. When flies encountered fruit treated with either 1 or 100 mg/ml feces extract, there were drastic and statistically significant reductions in tree residence time, mean time spent on fruit, and in the number of oviposition attempts or actual ovipositions when compared to the control treatment (clean fruit). These responses were almost identical irrespective of extract origin (i.e., fly species), indicating complete interspecific HMP cross-recognition by all three Anastrepha species tested. We discuss the ecological and practical implications of our findings.     

DIMBOA Glucoside, a Wheat Chemical Defense, Affects Host Acceptance and Suitability of Sitobion avenae to the Cereal Aphid Parasitoid Aphidius rhopalosiphi

The influence of hydroxamic acids (Hx), plant secondary metabolites associated with aphid resistance in wheat, on the host acceptance and suitability of the aphid Sitobion avenae to the cereal aphid parasitoid Aphidius rhopalosiphi was evaluated. Aphids showed a reduction in mean relative growth rate and in body size in the wheat cultivar with higher Hx level. Reduction in aphid size was related to a decreased success in avoiding parasitoid oviposition. A minor increase in A. rhopalosiphi developmental time was observed in aphids feeding on the higher Hx cultivar. Experiments with different concentrations of DIMBOA glucoside, the main Hx in wheat, in artificial diets showed an increase in parasitoid developmental time at the highest concentration, with no change in other performance variables. The evidence is discussed in relation to the compatible utilization of host-plant resistance and biological control in integrated pest management.     

Foraging Behavior and Microhabitat Use by Spiny Mice, Acomys cahirinus and A. russatus, in the Presence of Blanford's Fox (Vulpes cana) Odor

We investigated the responses of common and golden spiny mice (Acomys cahirinus and A. russatus, respectively) to the fecal odor of Blanford's fox (Vulpes cana), a predator of Acomys, which overlaps in habitat use with the mice. Neither species of mouse showed a significant response to the presence of fox odor compared with the presence of the fecal odor of a local herbivore (Nubian ibex, Capra ibex nubia). One explanation is that the impact of predation from V. cana may be sufficiently low that the cost of avoidance, in terms of missed feeding opportunities, conveys little selective advantage. Alternatively, fecal odor may not provide a focused cue of immediate danger for spiny mice. The diurnal A. russatus showed a stronger (near significant) response than the nocturnal A. cahirinus to fecal odor of this nocturnal predator. This may be a legacy of the underlying nocturnal activity rhythm of A. russatus or may indicate a generally more cautious response to predator odors, as A. russatus has a much stronger preference for sheltered microhabitats than A. cahirinus.     

Use of odor baits in traps to test reactions to intra- and interspecific chemical cues in house mice living in outdoor enclosures

House mice (Mus musculus) living in outdoor enclosures were tested for urinary chemical cue preferences using odor-baited traps. In the first experiment, with only volatile cues available, odors from conspecific males and females of various age classes and reproductive conditions were tested; no preferences were exhibited. In the second experiment mice had both nonvolatile and volatile cues available from the same sources as in experiment I. All age and sex class and female reproductive condition groups exhibited odor cue preferences except juvenile females. There were no specific odor cue preferences exhibited by any of the responder types with regard to odors from juvenile females. In the third and fifth experiments, mice were presented with nonvolatile plus volatile or only volatile urine odor cues, respectively, from four genera,Mus, Peromyscus, Microtus, andHomo. Mice of all age classes and both sexes preferredMus musculus odor, were neutral towardMicrotus ochrogaster odor, and avoided odors fromPeromyscus leucopus andHomo sapiens; these patterns were the same regardless of whether only volatile or both volatile and nonvolatile cues were presented. The fourth and sixth experiments involved testing volatile cues only and volatile cues plus nonvolatile cues from human sweat or feces from dogs, cats, or shrews. Mice avoided the human sweat and feces from cats and shrews, but were neutral toward the odor of dog feces. There were effects on whether mice were trapped in the interior of the enclosure or on the perimeter for some odors tested in these six experiments. The findings provide insights regarding possible functions of odor cues in the behavioral ecology of house mice. Odor-baiting traps can be an effective tool with respect to testing some, but not all questions pertaining to olfactory cues and house mouse social biology.     

Identification of Volatile Compounds Used in Host Location by the Black Bean Aphid, <Emphasis Type="Italic">Aphis fabae</Emphasis>

Behavioral and electrophysiological responses of winged Aphis fabae to volatiles of faba bean, Vicia faba (var. Sutton dwarf), plants were studied and semiochemicals used in host location were identified. In olfactometer bioassays, aphids spent significantly more time in the region of the olfactometer where V. faba volatiles from an intact plant were present than in control regions with clean air. This response also occurred when an air entrainment sample of a V. faba plant was used as the odor source. Coupled gas chromatography-electroantennography revealed the presence of 16 electrophysiologically active compounds in the air entrainment sample. Fifteen of these were identified as (Z)-3-hexen-1-ol, 1-hexanol, (E)-2-hexenal, benzaldehyde, 6-methyl-5-hepten-2-one, octanal, (Z)-3-hexen-1-yl acetate, (R)-(-)-linalool, methyl salicylate, decanal, undecanal, (E)-caryophyllene, (E)-beta-farnesene, (S)-(-)-germacrene D, and (E,E,)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. An olfactometer response was observed to a 15-component synthetic blend that comprised all identified compounds at the same concentration and ratio as in the natural sample, with the aphids spending significantly more time in the treated regions of the olfactometer where volatiles were present than in the control regions. These data are discussed in the context of insect host location and crop protection.     

Orientation of boll weevil,Anthonomus grandis boh. (Coleoptera: Curculionidae), to pheromone and volatile host compound in the laboratory

Behavioral responses of male and female boll weevils to the aggregation pheromone, grandlure, and the major volatile of cotton, -bisabolol, were investigated using a new dual-choice olfactometer. Dosage-response experiments revealed both males and females to be attracted by the aggregation pheromone at the 1.0 g dosage. However, only males were attracted to -bisabolol (1.0 g). Both sexes were repelled by the highest dosage of-bisabolol tested (10 g). In preference experiment, males chose grandlure over -bisabolol, while both sexes chose the combination of grandlure + -bisabolol over -bisabolol alone. There was some evidence for synergism between pheromone and plant odor for the females. The results correlate well with previous electrophysiological and behavioral experiments.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Roles of amino acids,protein, and fiber in leaf-feeding resistance of corn to the fall armyworm

The free amino acids have been shown by isolational work and choice bioassays to be more important than all other factors evaluated in defining leaf-feeding resistance of corn (Zea mays L.) to fall armyworm (FAW) [(Spodoptera frugiperda J.E. Smith)] larvae. 6-MBOA (6-methoxybenzoxazolinone) and maysin, toxins present in corn, were shown not to be significant factors for leaf-feeding resistance to first-instar FAW larvae because of their low concentrations in the whorl. Amino acid analysis showed that while the ratios of the essential amino acids in susceptible (S) and resistant (R) lines were similar, there were differences in the nonessential amino acids, particularly aspartic acid, which was higher in R lines. Also, the ratio of essential amino acids to nonessential amino acids was important, being too low in expressed whorl leaf juice (obtained from V₈–V₁₀ growth stage plants) to support larval growth, although juice was stimulatory in choice tests. The total protein content of whorls in S lines was about 15% higher than in R lines, but the significance of this difference is uncertain, because nutritional tests showed that larval growth increased with total protein only up to 12% protein. Sugars were only slightly stimulatory. Thus, the amino acids along with higher hemicellulose content of R lines, established by us earlier, appear to explain much of the basis of resistance in corn to larval leaf-feeding of the FAW.