Acetophenone superior to verbenone for reducing attraction of western pine beetle Dendroctonus brevicomis to its aggregation pheromone

1 The western pine beetle Dendroctonus brevicomis LeConte (Coleoptera: Scolytidae) is one of the most damaging insect pests of ponderosa pines Pinus ponderosa Douglas ex P. & C. Lawson in Western U.S.A. We compared the effect of verbenone, a well known bark beetle anti‐aggregation pheromone, with that of acetophenone on the attraction of D. brevicomis to its aggregation pheromone in a ponderosa pine forest in northern California. We tested the D. brevicomis aggregation pheromone alone and with three different release ratios of the aggregation pheromone (attractant) to verbenone or acetophenone (1 : 1, 1 : 2 and 1 : 5). 2 All treatments containing acetophenone or verbenone resulted in a significant reduction in the catch of D. brevicomis relative to the aggregation pheromone alone. When beetle responses to the three verbenone or three acetophenone treatments were pooled, the pooled verbenone treatment caught more D. brevicomis than the pooled acetophenone treatment. 3 There was no significant difference in the number of D. brevicomis caught among the three release rates of verbenone. By contrast, the 1 : 2 attractant : acetophenone ratio attracted significantly more D. brevicomis than the traps with the 1 : 5 attractant : acetophenone ratio. 4 Attraction of a major predator, Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), to the aggregation pheromone of D. brevicomis was reduced by verbenone, but not by acetophenone. Moreover, the T. chlorodia : D. brevicomis ratio for the pooled acetophenone treatment was 1.7‐fold greater than that for the attractant alone and two‐fold greater than the ratio for the pooled verbenone treatment, suggesting that acetophenone would not disrupt populations of this natural enemy. The importance of anti‐attractants in the biology of D. brevicomis and other bark beetles is discussed.     

Male specific natural products in the bug, Leptoglossus phyllopus: Chemistry and possible function

In the Coreoidea and some allied groups, male adults possess an abdominal gland opening through a midventral ostiole in the 7–8th abdominal intersegmental membrane. Using a GC-MS system, the following aromatic volatiles were identified in the abdominal gland secretion from males of the leaf footed bug, Leptoglossus phyllopus: guaiacol, benzyl alcohol, syringaldehyde, methyl p-hydroxybenzoate, acetosyringone, and vanillin. Males from which the glands were removed still mated and were competitive with control males for a limited number of females. The ventral abdominal gland secretion may act as a long-range attractant of females. The possibility that attraction of females by males in Heteroptera is an adaptation facilitating colonization of successional habitats is discussed.     

Olfactory memory in the mosquito Culex quinquefasciatus

The cosmotropical urban mosquito Culex quinquefasciatus Say (Diptera: Culicidae) uses chemical cues to locate suitable water pools for oviposition. Although gravid females are innately attracted to or repelled by certain compounds, this study found that an individual mosquito's preferences for these odours could be altered greatly by prior experience. Mosquitoes reared in water containing skatole, at a level normally repellent to ovipositing females, preferred to oviposit in water containing that compound rather than in water with an otherwise attractive odour compound (P-cresol). This behaviour occurred regardless of whether mosquitoes were tested individually or in groups of up to 50 per cage. The F1 progeny of conditioned mosquitoes did not exhibit the parental preference, but were as susceptible to conditioning as their parents. Moreover, rearing mosquitoes in infusions of hay or animal (guinea-pig) faeces produced a similar although less dramatic change, such that the innate propensity for hay infusion could be cancelled by rearing in guinea-pig faeces infusion. The results demonstrated a change in odour preference by Cx. quinquefasciatus following exposure to the odour during development or pupal eclosion, suggesting that some form of larval conditioning or early adult imprinting occurred. Precisely when that conditioning occurred remains to be determined.     

Behavioural responses of Varroa destructor (Acari: Varroidae) to extracts of larvae, cocoons and brood food of worker and drone honey bees, Apis mellifera (Hymenoptera: Apidae)

Abstract. Varroa destructor is a parasitic mite of the honey bee species Apis cerana Fabr . and A. mellifera L. Mature females reproduce on the immature stages of their hosts, producing more viable female offspring on drone hosts than on worker hosts. Thus, immature drones are more likely to be infested with mites than immature workers. To investigate the hypothesis that differences in host chemistries underlie the biased distribution of mites between worker and drone brood, the arrestment responses of mites to solvent extracts of a number of stimuli normally encountered by a mite during its life cycle were measured. Mites were arrested by cuticular extracts of worker and drone larvae obtained at 0, 24 and 48 h prior to the time when cell capping is completed. Mites were also arrested by extracts of worker and drone, brood food and cocoons, and by a blend of synthetic fatty acid esters previously shown to be active in the host acquisition process. In a wind tunnel bioassay, mites were attracted to odours from living fifth-instar worker and drone larvae, but not to volatiles from cocoons, brood food or a blend of fatty acid esters. The sex of the host was not an important factor affecting the behavioural responses of the mites in any assay. We conclude that host kairomones play a role in the host acquisition process, but we found no evidence to support the hypothesis that mites use these substances to differentiate between worker and drone brood.     

Responses of a generalist and a specialist parasitoid (Hymenoptera: Eucoilidae) to Drosophilid larval kairomones

Foraging parasitoids are thought to need more specific information than generalists on the presence, identity, availability, and suitability of their insect host species. In the present paper, we compare responses to host kairomones by two phylogenetically related parasitoid species that attack Drosophilidae and that differ in the width of their host range. As predicted, the behavioral response of the parasitoids to host kairomones reflected their difference in host range. The response of the specialist parasitoid Leptopilina boulardiwas restricted to contact kairomones from its natural hosts and one closely related species. In contrast, the generalist parasitoid Leptopilina heterotomaresponded to contact kairomones of a variety of Drosophilidae species.     

Study on foraging mechanism of leeches with different feeding habits based on chemoreception and foraging behavior

The leeches Whitmania pigra and Hirudo nipponia live in similar environments but have different feeding habits. At present, there are few studies of the foraging mechanism of leeches with different feeding habits. In this study, we first used maze tests to show that these two species of leeches could locate and distinguish their prey through chemosensory activity without mechanical stimulation. However, the two leech species have different foraging behaviors: Individuals of W. pigra move slowly and repeatedly adjust direction through probing and crawling to detect the location of prey (snails), whereas individuals of H. nipponia move quickly, and after determining the location of food (porcine blood), they quickly swim or crawl to the vicinity of their prey. Scanning electron microscopy (SEM) revealed that there are two types of sensory cilia and pore structures related to mucus secretion in the heads of both leeches. There are two differently sized types of chemoreceptors on the dorsal lip in W. pigra, which may have different functions during foraging, whereas in H. nipponia there is only one type of chemoreceptor, which is small. We detected the chemical components in the natural food of these two leech species by UHPLC–MS. There were 934 metabolites in the body fluid of snails and 751 metabolites in porcine serum; five metabolites unique to the body fluid of snails and to porcine serum were screened as candidate feeding attractants. Of these metabolites, betaine and arginine effectively attracted individuals of W. pigra and H. nipponia, respectively. In summary, leeches with different feeding habits use chemoreceptors to sense external chemical signals when foraging, and there are significant differences between species in foraging behavior, chemoreceptors, and attractants.     

Behavioral and physiological responses of Diaeretiella rapae to semiochemicals

Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae) parasitizes many aphid species, including cabbage aphids on cruciferous crops and Russian wheat aphids on cereal crops. We investigated the olfactory perception of D. rapae to semiochemicals that may be encountered in these two environments while searching for hosts or for mates. We conducted electroantennogram and flight-tunnel experiments on male and female D. rapae and found marked differences between sexes. Cruciferous volatiles elicited physiological and behavioral responses by females but not by males. Males and females responded similarly to (Z)-3-hexen-1-ol, a component of green-leaf volatiles, in both electroantennogram and flight-tunnel assays. Female wasps responded similarly regardless of prior oviposition experience or population origin. Likewise, mating history and aphid presence did not increase responsiveness toward these semiochemicals.     

ISOLATION, IDENTIFICATION AND SYNTHESIS OF THE FEMALE SEX PHEROMONE OF THE TEA TUSSOCK MOTH, EUPROCTIS PSEUDOCONSPERSA (LEPIDOPTERA: LYMANTRIDAE)

Abstract The sex attractant pheromone of the tea tussock moth, a serious economic pest of tea plantations in southern China, has been identified as 10,14-dimethylpentadecyl isobutyrate. A synthesis of the racemic form of the pheromone was developed, and traps baited with the synthetic compound at doses of 40–1000 micrograms captured male moths. The synthetic pheromone was as effective as a trap bait as, virgin female moths, or extracts of female moths.     

Effect of substrate formulation on the efficacy of the pea moth, Cydia nigricana, sex pheromone lures

Field experiments have shown that the activity of (E,E)-8,10-dodecadien-1-yl acetate, the sex pheromone of the pea moth, Cydia nigricana (F.) (Lepidoptera, Tortricidae), is significantly affected by the type of rubber substrate used for the preparation of dispensers. Rubber substrates cured with elemental sulphur or accelerators based on organic sulphur compounds isomerized pea moth pheromone faster than rubber substrates cured by organic peroxides. The degree of isomerization increased during field use and/or storage. Average catches of males were further dependent on the release rate of pheromone from the dispenser. In a 2×3 factorial experiment arranged in 6×6 Latin square design a statistically highly significant dispenser x dose interaction was demonstrated (P<0.01).

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Résumé Dans la nature, l'action de (E,E)-8,10-dodécadien-1-yl-acétate, phéromone sexuelle de C. nigricana F., est significativement modifiée par le type de caoutchouc utilisé poùr la réalisation du diffuseur. Le caoutchouc vulcanisé du soufre ou avec des accélérateurs à base de composés soufrés isomérise la phéromone sexuelle de C. nigricana plus rapidement que le caoutchouc vulcanisé avec des péroxydes organiques. Le taux d'isomérisation augmente pendant l'utilisation dans la nature et/ou pendant le stockage. Les captures moyennes de mâles dépendent avant tout de la libération de la phéromone par le diffuseur. Une étude de 2×3 facteurs organisée en carré latin (6×6) a mis en évidence une interaction hautement significative entre diffuseur et dose (P<0,01).

     

Host plant choice and location by larvae of the wheat bulb fly (Delia coarctata)

Wheat bulb fly (Delia coarctata Fallen, Diptera: Anthomyiidae) is an important pest of winter wheat in the eastern half of the UK, and in northern and eastern Europe. The larvae must find a host plant and invade a tiller soon after hatching in late January. Chemical controls are costly and weather conditions may reduce their efficacy or prevent their application. Post‐emergence control relies on organophosphate insecticides, which may soon be withdrawn due to concerns about their negative health and environmental effects. Winter wheat (Triticum aestivum L.) is the preferred cereal host, but other winter cereals and related grasses may also be attacked, while oats (Avena spp.) are shunned. In choice test bioassays, neonate larvae chose couch grass (Elytrigia repens (L.) Nevski syn. Elymus repens (L.) Gould, Agropyearon repens (L.) Beauv.) seedlings and exudates over wheat seedlings and exudates, and exhibited geotaxis and negative phototaxis. Analysis of larval trails in choice test bioassays of seedling exudates showed that couch exudates are more attractive than wheat exudates, and that wheat exudates are more arrestant than couch exudates. This suggests that infochemicals isolated from couch, wheat, and oats could be used in wheat bulb fly control; possible delivery mechanisms are discussed. These findings, previous research, and a comparison of the phenologies and geographical distributions of D. coarctata and its hosts suggest that E. repens is the natural host of D. coarctata.