Synthesis of sex pheromone components of the forest tent caterpillar,Malacosoma disstria (Hübner) and of the western tent caterpillar,Malacosoma californicum (Packard)

All four geometrical isomers of 5,7-dodecadien-1-ol have been stereoselectively synthesized by using Wittig condensation reactions. (5 Z,7E)-5,7-Dodecadien-1-ol and its corresponding aldehyde are components of the sex pheromone of the forest tent caterpillar. (5 E,7 Z)-5,7-Dodecadienal is a component of the pheromone of the western tent caterpillar. These compounds have been successfully tested in the field.     

Reassessment of the roles of the peritrophic envelope and hydrolysis in protecting polyphagous grasshoppers from ingested hydrolyzable tannins

We examined several of the mechanisms that have been reported to enable polyphagous grasshoppers (Orthoptera: Acrididae) to tolerate ingested hydrolyzable tannins: hydrolysis, adsorption on the peritrophic envelope, and peritrophic envelope impermeability. None of these mechanisms explain the tolerance ofMelanoplus sanguinipes to ingested tannic acid. In this species, tannin hydrolysis was 12–47% complete, adsorption accounted for less than 1% of the tannic acid contained in the midgut, and the peritrophic envelope was permeated by several gallotannins. The foregut is the main site for the chemical transformation of tannic acid in this species. InPhoetaliotes nebrascensis, hydrolysis was more extensive (82% complete), but the peritrophic envelope was readily permeated by two gallotannins. Oxidizing redox conditions were found in the guts of both species, and ingested tannins were oxidized inM. sanguinipes. We hypothesize that the tolerance of some polyphagous grasshoppers to ingested hydrolyzable tannins may be the consequence of their ability to tolerate the reactive oxygen species generated by polyphenol oxidation, whereas others may rely on rapid and extensive hydrolysis.     

Specificity of trail markers of forest and eastern tent caterpillars

Exploratory trails deposited on paper strips by the forest tent caterpillar (FTC),Malacosoma disstria Hubner, and the eastern tent caterpillar (ETC),M. americanum (Fabricius), as well as extracts of these trails, readily elicited interspecific trail-following behavior. In 2-choice tests involving simple Y mazes constructed from these paper strips, the caterpillars of both species preferred by approximately 31 the trails of the FTC. Studies involving whole colonies of the ETC maintained under nearnatural conditions in the laboratory, however, indicated that the trails deposited by successful foragers of the ETC as they returned to their tent from feeding sites were more attractive than the exploratory trails of either the ETC or FTC. The pronounced interspecific response of these congeners to each other's trails suggests that they utilize either qualitatively similar or identical trail-marking chemicals. Both species preferred their own trails to those ofArchips cerasivoranus (Fitch) (Tortricidae), providing the first evidence that more distantly related lepidopterous larvae utilize distinct trails.     

Phenolic Compounds in Red Oak and Sugar Maple Leaves Have Prooxidant Activities in the Midgut Fluids of <Emphasis Type="Italic">Malacosoma disstria</Emphasis> and <Emphasis Type="Italic">Orgyia leucostigma</Emphasis> Caterpillars

Phenolic compounds are generally believed to be key components of the oxidative defenses of plants against pathogens and herbivores. However, phenolic oxidation in the gut fluids of insect herbivores has rarely been demonstrated, and some phenolics could act as antioxidants rather than prooxidants. We compared the overall activities of the phenolic compounds in red oak (Quercus rubra) and sugar maple (Acer saccharum) leaves in the midgut fluids of two caterpillar species, Malacosoma disstria (phenolic-sensitive) and Orgyia leucostigma (phenolic-tolerant). Three hypotheses were examined: (1) ingested sugar maple leaves produce higher levels of semiquinone radicals (from phenolic oxidation) in caterpillar midgut fluids than do red oak leaves; (2) O. leucostigma maintains lower levels of phenolic oxidation in its midgut fluids than does M. disstria; and (3) phenolic compounds in tree leaves have overall prooxidant activities in the midgut fluids of caterpillars. Sugar maple leaves had significantly lower ascorbate:phenolic ratios than did red oak leaves, suggesting that phenolics in maple would oxidize more readily than those in oak. As expected, semiquinone radicals were at higher steady-state levels in the midgut fluids of both caterpillar species when they fed on sugar maple than on red oak, consistent with the first hypothesis. Higher semiquinone radical levels were also found in M. disstria than in O. leucostigma, consistent with the second hypothesis. Finally, semiquinone radical formation was positively associated with two markers of oxidation (protein carbonyls and total peroxides). These results suggest that the complex mixtures of phenolics in red oak and sugar maple leaves have overall prooxidant activities in the midgut fluids of M. disstria and O. leucostigma caterpillars. We conclude that the oxidative defenses of trees vary substantially between species, with those in sugar maple leaves being especially active, even in phenolic-tolerant herbivore species.     

Ethyl m-Digallate from Red Maple, Acer rubrum L., as the Major Resistance Factor to Forest Tent Caterpillar, Malacosoma disstria Hbn.

An ethanolic extract of red maple (Acer rubrum L.) leaves (RME) applied to trembling aspen (Populus tremuloides Michx.) leaves reduced feeding in choice test assays with forest tent caterpillar larvae (Malacosoma disstria Hbn.) (FTC), whereas a trembling aspen foliage extract, similarly applied, stimulated feeding. Compounds isolated from the RME were gallic acid, methyl gallate, ethyl gallate, m-digallate, ethyl m-digallate, 1-O-galloyl--D-glucose, 1-O-galloyl--L-rhamnose, kaempferol 3-O--D-glucoside, kaempferol 3-O--D-galactoside, kaempferol 3-O--L-rhamnoside, kaempferol-3-O-rhamnoglucoside, quercetin 3-O--D-glucoside, quercetin 3-O--L-rhamnoside and quercetin 3-O-rhamnoglucoside, (–)-epicatechin, (+)-catechin and ellagic acid. All of the gallates, (–)-epicatechin, and kaempferol 3-O--L-rhamnoside deterred feeding on trembling aspen leaf disks when applied at 0.28 mg/cm². The two digallates deterred feeding by 90% and were the most effective. HPLC analysis indicated that ethyl m-digallate is present in amounts 10–100 × higher in RME (2.5–250 mg/g) than any other compound. Thus, ethyl m-digallate appears to be the major compound protecting red maple from feeding by FTC, with a minor contribution from other gallates.     

Insect antifeedant activity of clerodane diterpenoids against larvae ofSpodoptera Littoralis (Boisd.) (Lepidoptera)

Antifeedant activities of nine clerodane diterpenoids, isolated in this laboratory from different species ofAjuga plants, have been studied against larvae of Egyptian cotton leafwormSpodoptera littoralis (Boisd.) (Lepidoptera) by application of the leaf disk method. Evaluation of activity was carried out by calculating, at different time intervals, the feeding ratio (FR) from the relationship between the consumed areas of treated disks (CTD) and control disks (CCD); for comparison purposes a FR₅₀ defined as the FR at a CCD of 50% was established. Some compounds exhibited activity at a 0.01 g/cm² dose (0.3 ppm). Structure-activity relationships are discussed     

Feeding responses ofChilo partellus (Swinhoe) (Lepidoptera: Pyralidae) larvae to sorghum plant phenolics and their analogs

Phagostimulatory responses of third-instar larvae ofChilo Partellus to phenolic components identified in an ethyl acetate extract of the leaf whorls of 3-week-old plants ofSorghum bicolor cultivar IS 18363 were studied in no-choice bioassays. The major components in the extract were identified as 4-hydroxybenzaldehyde and 4-hydroxybenzoic acid, with 4-hydroxy-3-methoxycinnamic acid, 3,4-dihydroxycinnamic acid, and 4-hydroxycinnamic acid present in minor amounts. All but 4-hydroxycinnamic acid were stimulatory at the doses tested. 4-Hydroxybenzaldehyde was more stimulatory than other potential biogenetic analogs. Hydroxybenzoic acids generally elicited greater feeding response than cinnamic acids, and the pattern of oxygen substitution in the benzene ring was related to bioactivity.     

Identification of trail pheromone of larva of eastern tent caterpillarMalacosoma americanum (Lepidoptera: Lasiocampidae)

Previous studies have shown that larvae of the eastern tent caterpillar (Malacosoma americanum F.) mark trails, leading from their tent to feeding sites on host trees, with a pheromone secreted from the posterior tip of the abdominal sternum. 5-Cholestane-3,24-dione (1) has been identified as an active component of the trail. The larvae have a threshold sensitivity to the pheromone of 10^–11 g/mm of trail. Several related compounds elicit the trail-following response. Two other species of tent caterpillars also responded positively to the pheromone in preliminary laboratory tests.     

Copulation releaser pheromone in body scales of female whitemarked tussock moth,Orgyia leucostigma (Lepidoptera: Lymantriidae): Identification and behavioral role

The copulatory behavior of the male whitemarked tussock moth,Orgyia leucostigma, was released by extracts of female body scales applied to rubber septum models baited with a female sex pheromone gland. The major compounds in the scale extracts were identified by GC-MS as a series ofn-alkanes from C-21 to C-29. Of these,n-tricosane,n-tetracosane,n-pentacosane, andn-heptacosane, applied at 10 ng/septum, caused significantly more males to attempt copulation than hexane-treated controls. Mixtures of then-alkanes, resembling the composition in the scale extracts, were no better than the two most active alkanes,n-tetracosane andn-pentacosane, alone. The releaser effect of then-alkanes was dose dependent. EAG responses to the identifiedn-alkanes were small suggesting, along with the behavioral observations, that their perception occurred at very close range. Other factors releasing male copulatory behavior are discussed.     

Importance of quinolizidine alkaloids in the relationship between larvae ofUresiphita reversalis (Lepidoptera: Pyralidae) and a host plant,Genista monspessulana

Larvae ofUresiphita reversalis feed almost exclusively on legumes in the tribe Genisteae, which characteristically contain a variety of quinolizidine alkaloids. The larvae are aposematic, and onGenista monspessulana, a major host in California, they feed on the youngest leaves, at the periphery of the plant. These leaves, which were preferred over older foliage in choice tests, contained four to five times the level of alkaloid found in older leaves. The major alkaloids detected in these plants were dehydroaphylline andN-methylcytisine, together accounting for 74% of the total. Preliminary analyses showed the alkaloid profile of exuviae from larvae feeding on these plants was very similar to that of the plants. Two alkaloids, sparteine and cytisine, which are known components of some hosts ofU. reversalis, were phagostimulants for fifth-instar larvae when added to sucrose-impregnated glass-fiber disks. In addition, when sparteine was added to foliage ofG. monspessulana, effectively doubling the percent dry weight of alkaloid, the growth rate of late-instar larvae was positively affected. Cytisine added to plants had no discernible effect on growth of larvae. Alkaloid levels in larvae and in their frass were proportional to levels in the plants on which they fed. Although the majority of alkaloid was excreted, that which was sequestered by the insect was found entirely in the integument, possibly confering some protection from predators.     

Protective action of midgut catalase in lepidopteran larvae against oxidative plant defenses

Catalase activity was detected in the midgut tissues and regurgitate of several lepidopteran pests of the tomato plant. Greatest activity in the midgut was detected in larvalHelicoverpa zea, followed bySpodoptera exigua, Manduca sexta, andHeliothis virescens. We present evidence that catalase, in addition to removing toxic hydrogen peroxide, may inhibit the oxidation of plant phenolics mediated by plant peroxidases. Small amounts of larval regurgitate significantly inhibited foliar peroxidase activity via removal of hydrogen peroxide. Treatment of foliage with purified catalase nearly eliminated peroxidase activity and was superior as a larval food source compared to untreated foliage. Tomato foliar peroxidases oxidize an array of endogenous compounds including caffeic acid, chlorogenic acid, rutin, coumaric acid, cinnamic acid, and guaiacol. The oxidized forms of these compounds are potent alkylators of dietary and/or cellular nucleophiles (e.g., thiol and amino functions of proteins, peptides, and amines). When tomato foliar protein was pretreated with peroxidase and chlorogenic acid and incorporated in artificial diet, larval growth was reduced compared to larvae fed untreated protein. Thus, the diminution of peroxidase activity and removal of hydrogen peroxide by catalase may represent an important adaptation to leaf-feeding. The secretion of catalase in salivary fluid during insect feeding is also suggested to be a potential mechanism for reducing hydrogen peroxide formation as an elicitor of inducible plant defenses.     

Orientation behavior of second-instar larvae of eastern spruce budwormChoristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae) in a y-type olfactometer

A two-choice, wind-tunnel olfactometer was designed and contructed to determine whether second-instar eastern spruce budworm larvae,Christoneura fumiferana (Clem.), could detect and discriminate among host-plant volatiles. Volatiles of current year's growth ofPicea glauca were preferred over those ofP. rubens, P. mariana, or air.Abies balsamea was preferred overP. mariana or air.P. rubens andP. mariana were both preferred over air. Two-year-old growth ofP. glauca, A. balsamea, P. rubens, andP. mariana were all preferred over air. Current year's growth of these host evergreen species was usually preferred over former year's growth of the same species in each case.     

A trail pheromone from silk produced by larvae of the range caterpillarHemileuca oliviae (Lepidoptera: Saturniidae) and observations on aggregation behavior

Methylene chloride-extractable chemical(s) from range caterpillar larval silk facilitates trail-following and aggregation by early-instar larvae, but late-instar larvae are less responsive to the pheromone. Larval aggregation does not reduce water loss when larvae are exposed to low humidity, nor does aggregation prevent predation by the antFormica neoclara Emery. Grouped larvae gain weight and complete early stadia more rapidly as compared to solitary larvae. Aggregation may provide increased visibility to herbivores and increase the impact of urticating spines, thereby decreasing inadvertant predation.     

Fate of iridoid glycosides in different life stages of the Buckeye,Junonia coenia (Lepidoptera: Nymphalidae)

The buckeye butterfly,Junonia coenia (Lepidoptera: Nymphalidae), specializes on plants that contain iridoid glycosides. To determine the fate of these compounds in larvae, pupae, and adults of this species, we reared larvae on artificial diets with and without iridoid glycosides, and on leaves of a host plant,Plantago lanceolata (Plantaginaceae). Quantification by gas chromatography showed that newly molted third-, fourth-, and fifth-instar larvae reared on leaves ofP. lanceolata contained means of 5.13, 2.88, and 6.83% dry weight iridoid glycoside. In contrast, the mean iridoid glycoside concentration of actively feeding fifth-instar larvae was 0.28% dry weight, that of pupae was 0.19% dry weight iridoids, and adults contained no detectable iridoids. Feeding experiments suggested that this reduction in actively feeding larvae was due to the metabolism of iridoid glycosides.P. lanceolata leaves in these experiments contained a mean of 1.00% dry weight iridoid glycoside, with a 2:1 ratio of aucubin to catalpol. Calculation of iridoid consumption and utilization indices showed that larvae fed artificial diets consumed, digested, and sequestered aucubin and catalpol in similar ways. When these indices were calculated for larvae fed leaves ofP. lanceolata, catalpol was sequestered twice as efficiently as aucubin.     

Repellency of oral exudate to eastern and western spruce budworm larvae (Lepidoptera: Tortricidae)

A two-choice feeding bioassay was used to investigate the intra-specific repellency of the larval oral exudate of eastern and western spruce budworms,Choristoneura fumiferana (Clem.) andC. occidentalis Free., respectively. Results of the bioassay indicated that feeding behavior on artificial diet-drop feeding stations was modified in the presence of exudate, with feeding stations treated with conspecific exudate being avoided when an untreated station was available 3 cm away. Feeding was suppressed when a single, exudate-treated station was provided, or when the treated and untreated stations were separated by only 1 cm. The repellent effect functioned both inter- and intraspecifically. When induced to produce exudate,C. occidentalis larvae were not immediately repelled by either their own or other individuals' exudate. However, 24 hr after induction, test larvae were repelled by exudate from either source. In both species, larval oral exudate probably functions to repel conspecific competitors.     

A chemical trail factor from the silk of the eastern tent caterpillarMalacosoma americanum (Lepidoptera: Lasiocampidae)

The leaf-feeding larvae of the eastern tent caterpillarMalacosoma americanum (Fabricius) follow silk trails laid down on branches leading from their communal tent to distant foraging sites. The response of colonies reared in the laboratory under seminatural conditions to silk trails washed in methylene chloride and to chemical trails prepared from a solvent extract of their tent or trail silk, showed that one or more soluble components of their trail is essential to the elicitation of the following response. The demonstrated ability of the caterpillars to distinguish between old and newly reinforced silk trails most likely occurs in response to a temporal change in the detectable chemical properties of their trail.     

Chemical composition of North American bee propolis and biological activity towards larvae of greater wax moth (Lepidoptera: Pyralidae)

Bee propolis is a sticky amalgamation of plant resins collected by honeybees (Apis mellifera L.) and used in the hive for filling cracks and repairing combs. Propolis contains a diversity of compounds of plant origin, and is reported to have medicinal, antimicrobial, insecticidal, and phytotoxic properties. We examined the physical and chemical composition of North American samples of bee propolis from several sites in North America and tested for bioactivity against larvae of the greater wax moth (Galleria mellonella L.), a common apiary pest. The amount of methanol-extractable resin in samples from Ohio and Georgia ranged from 24% to 79% by weight. Propolis collected from hives in Ohio was more chemically diverse (over 30 compounds detected by paper chromatography) than material from south Georgia (fewer than 10 major compounds) and contained a lower proportion of methanol-insoluble beeswax. The paper chromatographic surveys revealed little variation in the chemical profile of specific hives over a six-month period and no differences between propolis from adjacent hives. Four flavonoids were identified from propolis collected in Ohio: kaempferol, galangin, 3,3-dimethoxyquercetin and 3-methoxykaempferol. When mixed into artificial diet, fractionated propolis reduced larval growth of the greater wax moth, but not dramatically. An array of phenolics reported from propolis (caffeic acid, chrysin, ferulic acid, galangin, kaempferol, and quercetin) were bioassayed individually for effects on larvae, but none reduced larval growth at the concentrations tested, suggesting that wax moths are tolerant of some phenolics in their diet.     

Sex pheromone of tomato pestScrobipalpuloides absoluta (Lepidoptera: Gelechiidae)

The sex attractant ofScrobipalpuloides absoluta females is a 90:10 mixture of (3E,8Z,11Z)-3,8,11-tetradecatrien-1-yl acetate and (3E,8Z)-3,8-tetradecadien-1-yl acetate. Tetradecadienyl acetates bearing 8Z,11Z; 3E,8Z; and 3E,11Z double bonds were synthesized by stereospecific procedures; the mass spectral and gas chromatographic properties of the 3E,8Z isomer were found to be congruent with those of the tetradecadienyl acetate fromS. absoluta. In wind tunnel bioassays, a 10:1 mixture of synthetic (3E,8Z,11Z)-3,8,11-tetradecatrien-1-yl acetate and (3E,8Z)-3,8-tetradecadien-1-yl acetate was highly attractive toS. absoluta males. Interestingly, the presence of (8Z,11Z)-8,11-tetradecadien-1-yl acetate (10%) inhibited the response to (3E,8Z,11Z)-3,8,11-tetradecatrien-1-yl acetate completely.     

Olfactory sensitivity of two sympatric species of rice leaf folders (Lepidoptera: Pyralidae) to plant volatiles

Electroantennograms (EAGs) were recorded from male and female moths of two sympatric leaf folder species,Cnaphalocrocis medinalis (Gue-née) andMarasmia patnalis Bradley (Lepidoptera: Pyralidae) to 91 volatile chemicals of plant origin. Responses of both leaf folder species were similar to all compounds except to three monoterpenes--myrcene, menthone, and isomenthone- and two sesquiterpenes-cis-nerolidol and isophytol. Response ofM. patnalis, an oligophagous leaf folder, to these compounds was higher compared with that of polyphagousC. medinalis. EAG responses of males to saturated and unsaturated aliphatic aldehydes were significantly higher than those of conspecific females in both species. A higher response ofC. medinalis males also was observed for 1-nonanol, 3-nonen-2-one, andtrans, trans-2,6-dimethyl-2,4,6-octatriene. In contrast, females of both species responded more to monoterpenes, borneol, isoborneol, and fenchyl alchohol. Response ofC. medinalis female was higher for terpinen-4-ol, carveol, dihydrocarveol, (–)-myrtenal, and perillaldehyde. In both species and sexes, high EAG responses were recorded for compounds of the green leaf odor complex. EAG responses to nonanal and hexanal were maximum among the aliphatic aldehydes while 1-hexanol elicited the highest response among the alcohols tested. EAG responses to terpene compounds-citronellal,-terpineol, and (–)-myrtenal-were equal to the response to 1-hexanol. While all compounds tested elicited a negative potential, thymol and carvacrol elicited a positive EAG potential. The EAG data are discussed with regard     

Enniatins fromFusarium avenaceum isolated from balsam fir foliage and their toxicity to spruce budworm larvae,Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae)

Material extracted from hyphae ofFusarium avenaceum, isolated from foliage of balsam fir,Abies balsamea, was toxic to spruce budworm larvae when incorporated into insect diet. The major insecticidal component of the toxic fraction was identified by chemical and spectroscopic methods as enniatin complex, rich in enniatin A/A₁. Possible ecological implications of these observations are considered.