Intensification and prolongation of host searching inLeptopilina heterotoma (Thomson) (Hymenoptera: Eucoilidae) through a kairomone produced byDrosophila melanogaster

A chemical cue (kairomone) of the host, larvae ofDrosophila, was found to influence patch-time allocation of the parasiteLeptopilina heterotoma. This kairomone is soluble in water and chloroform. The kairomone was purified using thin-layer chromatography. The concentration of the kairomone increases with an increasing number of hosts. The parasites may use presence and concentration of the kairomone as cues to determine patch-time allocation.     

Host-recognizing kairomones for parasitic wasp,Anisopteromalus calandrae,from larvae of azuki bean weevil,Callosobruchus chinensis

Host-recognizing kairomones for the stinging behavior of the parasitic wasp, Anisopteromalus calandrae, were identified on host azuki bean weevil larvae, Callosobruchus chinensis (L.). The kairomones were extracted with acetone from Chinese green beans, from which emerged wasps and host weevils had been removed. The kairomones are a mixture of triacylglycerols and fatty acids, each of which is separately active, and with no observable synergistic effect between them. These compounds are known to be constituents of an oviposition-marking pheromone of host azuki bean weevils. However, they differ from the previously reported saturated hydrocarbons and diacylglycerols of the kairomone that another parasitic wasp, Dinarmus basalis, uses for the host recognition of C. chinensis. Thus, A. calandrae and D. basalis selectively utilize different constituents of the oviposition-marking pheromone of C. chinensis as host-recognizing kairomones.     

Host egg kairomones essential for egg-larval parasitoid,Ascogaster reticulatus watanabe (Hymenoptera: Braconidae)

An artificial egg with a Parafilm membrane was devised for the oviposition ofAscogaster reticulatus Watanabe (Hymenoptera: Braconidae), an egg-larval parasitoid of the smaller tea tortrix,Adoxophyes sp. (Lepidoptera: Tortricidae). Both external and internal kairomones were essential. The external kairomone, needed for host location and acceptance, was extracted with 70% ethanol, and the internal kairomone, needed for oviposition, was extracted with water. Female parasitoids responded to the external kairomone and oviposited through the membrane into the artificial egg when the supernatant of host egg-mass homogenate was inside, whereas they did not when water or saline solutions were inside. Thus an internal kairomone is responsible for the oviposition in the host egg. The internal kairomone apparently was not specific for the host egg mass because oviposition activity was found not only in egg, larval, and pupal stages of the host, but also in larvae of other species of Lepidoptera and Coleoptera.     

Behavioral and biological responses ofCotesia marginiventris to kairomones of the fall armyworm,Spodoptera frugiperda

Potential kairomone sources of the fall armyworm (FAW),Spodoptera frugiperda (J.E. Smith), were bioassayed with females ofCotesia marginiventris (Cresson) in Petri dishes (10 cm diam). MatedC. marginiventris females, ranging in age from 1 to 3 days exhibited the most intense bioassay responses to potential sources of kairomone. Contacting a FAW-damaged corn leaf modified the pattern of movement inC. marginiventris from random to one exhibiting a significant increase in klinokinesis. No significant differences were present in kairomone responses of nonconditioned and conditioned parasitoids and parasitoid response to kairomones did not change throughout the photophase (0800–1800 hr). Removal of one, both, or the first eight antennal segments reduced or eliminated the response of the parasitoid to kairomones. Female parasitoids did not exhibit a preference for corn leaves damaged by a particular fall armyworm instar and parasitization rates were highest in larvae 48 hr old.Submitted in partial fulfillment of the requirements for Doctor of Philosophy, Department of Entomology and Nematology, University of Florida, Gainesville.     

Identification and synthesis of a kairomone inducing oviposition by parasitoidAphytis melinus from California red scale covers

The parasitoid waspAphytis melinus uses a kairomone from the cover of its scale host, California red scale (Aonidiella aurantii), as an oviposition stimulant. The kairomone was isolated from extracts of scale covers, and identified asO-caffeoyltyrosine by a combination of spectroscopic methods. The kairomone was synthesized, and the synthetic compound was determined to be as active as the chemical isolated from scale covers.     

Caterpillar Footprints as Host Location Kairomones for <Emphasis Type="Italic">Cotesia marginiventris</Emphasis>: Persistence and Chemical Nature

Herbivores walking over the epicuticular wax layer of a plant may leave tracks that disclose their presence to hunting predators or parasitoids. The braconid wasp Cotesia marginiventris is a solitary parasitoid of young noctuid caterpillars. It can locate potential hosts from a distance by orienting toward the scent of herbivore-damaged plants. Upon landing on the caterpillars’ food plant, the female parasitoid searches for further cues (kairomones) that confirm the presence of a suitable host. In a previous study, we showed that C. marginiventris recognizes the chemical footprints of absent Spodoptera frugiperda caterpillars on a leaf. Here, we report on the persistence and chemical nature of this host location kairomone. In a series of behavioral assays, we confirmed that caterpillars of S. frugiperda leave chemical tracks that elicit characteristic antennation behavior in C. marginiventris for up to 2 days. Both hexane extracts of caterpillar footprints and of the larvae’s ventral cuticle induced antennation and contained almost identical long-chain hydrocarbons, thus suggesting the prolegs and claspers as the kairomones’ main source. A series of linear C₂₁ to C₃₂ alkanes accounted for ca 90% of all identified compounds. Female wasps showed significant antennation responses on leaves treated with a reconstructed blend of these n-alkanes. However, wasp responses were relatively weak. Therefore, we presume that minor compounds, such as monomethyl-branched alkanes, which were also found, may contribute additionally to host recognition.     

Kairomonal activities of 2-acylcyclohexane-1,3 diones produced byEphestia kuehniella zeller in eliciting searching behavior by the parasitoidBracon hebetor (say)

2-Acylcyclohexane-1,3-diones produced in the mandibular glands ofEphestia kuehniella Zeller (Lepidoptera: Pyralidae) fifth instars acted as arrestment and host-trail following kairomones for the parasitoid,Bracon hebetor (Say) (Hymenoptera: Braconidae). The behavioral response of the parasitoids to the kairomone varied with kairomone concentration and distribution. However, only small differences in activity were noted for the different mandibular gland components.B. hebetor females that encountered filter paper patches impregnated with the kairomone exhibited antennation and probing behavior. Females followed trails formed with 2-[(Z,E)12,14-hexadecadienoyl]cyclohexane-1,3-dione in the same manner exhibited with host-made trails. At concentrations of 1.0 g/mm and above, trail following was interrupted by frequent probing.     

Effects on behavior ofApanteles melanoscelus females caused by modifications in extraction,storage, and presentation of Gypsy moth silk kairomone

Choice experiments were performed to investigate details of femaleApanteles melanoscelus (Ratzeburg) behavior when exposed to gypsy moth silk kairomone [Lymantria dispar (L.)] and to host larvae when kairomone is present. Female parasites only responded to the kairomone when it had been placed on thin strands such as cotton fibers. Both gypsy moth silk and silk glands contain the same or similar kairomones. Silk gland extracts were more active than head, alimentary canal, or hemolymph extracts of host larvae. Female responses decreased when low concentrations of silk gland extract or small numbers of treated fibers were presented to them. Silk gland extract was stable when frozen for 2 weeks, heated to 100 °C for 0.5 hr, freeze dried, or treated with 95% ethanol. The active component was nondialyzable. Silk deposited on the substrate increased host contacts and oviposition attempts, more so if wider areas were covered with silk, and even if the areas having silk were separated from the host. A theory of host selection inA. melanoscelus is proposed.Hymenoptera, Braconidae. Lymantria dispar L. (Lepidoptera: Lymantriidae).     

Mite predator responses to prey and predator-emitted stimuli

We found that the searching behavior of two acarine predators,Amblyseius fallacis andPhytoseiulus macropilis, for prey,Tetranychus urticae, is affected by the following stimuli: (1) prey silk and associated feces, whose combined physical and chemical properties elicit reduction in the rate of predator movements and longer halts; (2) kairomone extracted from prey silk and associated feces, which, upon contact, elicits frequent predator return to prey-inhabited locales; and (3) predator-emitted marking pheromone, which elicits shorter duration of search in presearched prey locales. We also found that treatment of filter paper with prey kairomone or silk enhanced predator location of prey eggs, leading us to speculate that application of synthetic prey kairomone could be useful in pest management programs.     

Influence of trichome exudates from species ofLycopersicon on oviposition behavior ofHeliothis zea (Boddie)

Cage experiments revealed that accessions of the wild tomato speciesLycopersicon hirsutum were preferred sites for oviposition byHeliothis zea. Hexane extracts from the leaves ofL. hirsutum were also preferred sites of oviposition in choice experiments among extracts from severalLycopersicon species. Extracts ofL. hirsutum were still biologically active several days after application, indicating that the phytochemical(s) involved are relatively stable and of low volatility. Gas Chromatographic analysis of leaf hexane extracts from 12 different accessions of theL. hirsutum complex and three tomato cultivars revealed substantial qualitative and quantitative variation in the chemical composition of these extracts. Comparison of these results with extract oviposition studies implicate a group of structurally related compounds as the active agents. Mass spectroscopy has tentatively identified these compounds as sesquiterpenes with the chemical formula C₁₅H₂₂O₂. These compounds are apparently synthesized and secreted from glandular trichomes on the leaf surface. These phytochemicals did not stimulate ovipositional behavior in females of the cabbage looper,Trichoplusia ni. The existence of genetic variation for the presence and amount of kairomones that serve as cues for insect orientation and oviposition could be utilized in a breeding program to develop tomato cultivars with genetically modified allelochemic profiles that would disrupt the sequential behavioral processes of insect host-plant selection.     

Behavioral and Chemical Investigations of Contact Kairomones Released by the Mud Dauber Wasp <Emphasis Type="Italic">Trypoxylon politum</Emphasis>, a Host of the Parasitoid <Emphasis Type="Italic">Melittobia digitata</Emphasis>

Contact kairomones from the host mud dauber wasp Trypoxylon politum Say (Hymenoptera: Crabronidae) that mediate behavioral responses of its ectoparasitoid Melittobia digitata Dahms (Hymenoptera: Eulophidae) were investigated. Chemical residues from host by-products, the cocoon, and the meconium, induced arrestment behavior of macropterous female parasitoids, while those from the host stage attacked, i.e., the prepupa, did not. Melittobia digitata response to polar and apolar extracts of host by-products indicated kairomone(s) solubility mainly in hexane. GC and GC/MS analysis of cocoon and meconium apolar extracts revealed a mixture of linear carboxylic acids from C₆ to C₁₈, and both extracts contained almost identical compounds. When a reconstructed blend of host by-product carboxylic acids was tested, M. digitata females showed only a weak response, thus suggesting that other unidentified compounds present in small quantities also may be involved. Melittobia digitata’s response to contact kairomones was innate and not affected by previous host exposure experience. Our results provide evidence of contact kairomone exploitation in the genus Melittobia. The ecological significance of these findings in the host selection process of M. digitata is discussed.     

Earthworm mucus stimulates oviposition in a predatory fly (Diptera: Anthomyiidae)

Coenosia tigrina larvae feed on earthworms. We hypothesized that earthworm mucus contains a kairomone that stimulates oviposition behavior in adultC. tigrina females, thus minimizing the search area in the soil required for newly eclosed larvae to find earthworms. In bioassays, adult females responded with extension of the ovipositor 25–43% of the time to earthworm-mucus-soaked filter paper disks compared to 6–7% in response to water-soaked disks. Ovipositor extension on mucus-soaked disks was followed by egg-laying 29% of the time and 0% of the time on water-soaked disks. Egg-laying byC. tigrina followed a diurnal periodicity, with most eggs laid in the latter half of the photophase even in the absence of earthworm mucus. More eggs were deposited from 1600 to 1800 hr by females given access to earthworm mucus during that period than were deposited by females not given access. There was no difference in the number of eggs deposited from 0600 to 0800 hr, by females given access to earthworm mucus or not. This is a time of day when few eggs are normally laid. This paper is the first report of an earthworm-produced kairomone in an insect-earthworm interaction. The kairomone may have potential for enhancing biological control of the onion maggot,Delia antiqua, which is a prey of adultC. tigrina.     

Alteration of kairomone-induced antipredator response of the freshwater amphipod Gammarus roeseli by sediment type

The importance of sediment type and of kairomones released by juvenile burbot (Lota lota) on behavioral responses of the freshwater amphipod Gammarus roeseli was studied in laboratory experiments. In the absence of kairomones, G. roeseli preferred coarse substrates; the highest preference was shown for the most coarse sediment. In the presence of kairomones, the amphipods preferred the less-coarse substrate pebbles over gravel. This difference is an effective antipredator response; G. roeseli is able to hide efficiently in the interstices of the pebbles. Juvenile burbot have a low foraging efficiency on pebbles and preferentially forage in the interstices of coarser sediments. G. roeseli responded differently to kairmones in different sediment types. The amphipods decreased their activity only in pebbles. In gravel, the rate of exploration behavior increased, and on a bare surface, the area containing fish kairomones was avoided.     

Parasitic Wasp, Dinarmus basalis, Utilizes Oviposition-marking Pheromone of Host Azuki Bean Weevils As Host-Recognizing Kairomone

A host-recognizing kairomone responsible for the stinging behavior of the parasitic wasp, Dinarmus basalis, was studied. Fresh azuki beans coated with an acetone extract of the azuki beans, from which both emerged wasps and their host weevils were removed, elicited stinging behavior from female wasps. The kairomone is a mixture of saturated hydrocarbons and diacylglycerols, both of which are required for activity. The kairomone is composed of normal and methyl-branched hydrocarbons with carbon numbers ranging from 25 to 35, most of which are known as the hydrocarbon constituents of an oviposition-marking pheromone of the host azuki bean weevils, Callosobruchus chinensis. This indicates that D. basalis utilizes the oviposition-marking pheromone of its host weevils as a host-recognizing kairomone.     

Kairomone strains of Euclytiaflava (Townsend), a parasitoid of stink bugs

Tachinid flies commonly use the pheromones and allomones of stink bugs (Pentatomidae) as host-finding kairomones. Pheromone-baited traps for predaceous (Podisus spp.) and phytophagous (Euschistus spp.) pentatomids were used to obtain tachinid parasitoids in order to study the semiochemical relationships between these parasitic flies and their stink bug hosts. Gas chromatography–electroantennogram detector (GC-EAD) experiments and field tests were conducted to determine if pheromone strains of the tachinids, Euclytia flava and Hemyda aurata, occur in nature and to determine if the EAD-active compound, (E)-2-octenal (a common allomone compound of Heteroptera), affects attraction of tachinid parasitoids to synthetic Podisus pheromones. Addition of (E)-2-octenal to Podisus spp. synthetic pheromones in field traps tended to suppress attraction of the bugs, whereas (E)-2-octenal decreased, did not affect, or increased pheromonal attraction of tachinid parasitoids depending on the host species pheromone being tested and the habitat type in which the traps were deployed. Evidence from GC-EAD experiments of E. flava associated with different stink bug hosts suggested that kairomone-strains of this tachinid parasitoid coexist naturally. The significance of cryptic kairomone strains of parasitoids for classical biological control is disc ussed, and the mechanisms whereby parasitoids evolve kairomonally mediated host-shifts is considered.     

Kairomones and their use for management of entomophagous insects

Data are presented that demonstrate the responsiveness ofChrysopa carnea Stephens larvae to kairomones in the moth scales ofHeliothis zea (Boddie). Rates of predation byC. carnea on eggs ofH. zea were increased whenH. zea moth scales or a hexane extract of the scales was applied to the search area under laboratory and greenhouse conditions.Lepidoptera:NoctuidaeNeuroptera:ChrysopidaeIn cooperation with the University of Georgia College of Agriculture Experiment Stations, Coastal Plain Station, Tifton, Georgia 31794.Mention of a commercial or proprietary product in this paper does not constitute endorsement of this product by the USDA.     

Identification and Synthesis of a Kairomone Mediating Host Location by Two Parasitoid Species of the Cassava Mealybug Phenacoccus herreni

Two encyrtid species, Acerophagus coccois and Aenasius vexans, parasitoids of the cassava mealybug Phenacoccus herreni use a contact kairomone from the body surface of their host as a host-location stimulant. The kairomone was synthesized and identified as O-caffeoylserine based on a combination of chromatographic methods. The synthetic compound was determined to be active.     

A long-range attractant kairomone for egg parasitoidTrissolcus basalis,isolated from defensive secretion of its host,Nezara viridula

A short-chain ,-unsaturated aldehyde, (E)-2-decenal, present in the defensive metathoracic gland ofNezara viridula (L.) (Heteroptera: Pentatomidae), stimulates a behavioral response in the egg parasitoidTrissolcus basalis (Woll.) (Hymenoptera: Scelionidae). Preliminary studies showed thatT. basalis are attracted to an area containing adultN. viridula, but we also found that femaleT. basalis would examine and probe glass beads coated with an acetone extract of the metathoracic gland from males or females. Using this bioassay, the kairomone was isolated by bioassay directed by preparative gas chromatography and identified by NMR and mass spectrometry as (E)-2-decenal. The biological activity of the identified aldehyde was compared with analogs to determine specificity. An unstable Z isomer was found to be more active but not present in detectable or behaviorly relevant levels in the host, based on the bell-shaped dose-response curve of the two isomers. An investigation was also designed to determine if theE isomer was also responsible for the egg recognition kairomone activity previously reported. However, no 2-decenal isomers were detected in host egg extracts and the chemical characteristics of the 2-decenal isomers differ from the unidentified egg recognition kairomone. The role of the (E)-2-decenal in attracting femaleT. basalts toN. viridula was demonstrated in a Y-tube olfactometer; this alk-2-enal appears to act as a long-range kairomone orientingT. basalis toNezara populations.     

Effect of kairomones from egg and female adult stages ofOstrinia nubilalis (Hübner) (Lepidoptera,Pyralidae) onTrichogramma brassicae Bezdenko (Hymenoptera,Trichogrammatidae) female kinesis

Volatile chemicals emanating from the different developmental stages ofOstrinia nubilalis Hübner (Lepidoptera, Pyralidae) increase the mobility ofTrichogramma brassicae Bezdenko (Hymenoptera, Trichogrammatidae) in a linear airflow olfactometer. In this paper, we have demonstrated that airborne chemicals from egg masses and virgin females during calling activity stimulate an intensive search behavior byTrichogramma females. On the other hand, emanations from mated females with extruded abdominal tips do not incite the parasitoid's movement. For the moment we cannot elucidate, with these bioassays, the real role of these kairomones as attractants, guides, stimulants, or retainers.     

Brook Char (Salvelinus fontinalis) Can Differentiate Chemical Alarm Cues Produced by Different Age/Size Classes of Conspecifics

A wide diversity of aquatic organisms release chemical alarm cues when captured by a predator. For most animals, it is not known whether the specific chemicals that comprise the alarm cue are conserved as prey animals age. In this study, we tested whether brook char (Salvelinus fontinalis) can differentiate alarm cues produced by individuals of different ages/sizes. In separate laboratory experiments we exposed small brook char and large brook char to chemical alarm cues from small brook char, large brook char, and a control of swordtails (Xiphophorus helleri). Both small and large brook char responded with antipredator behavior to chemical alarm cues from both small and large char, but not to those from swordtails. Small char responded with a greater response intensity to cues of small char than to cues of large char. In contrast, large char responded with a greater response intensity to cues of large char than to cues of small char. These results suggest that chemical(s) that act as the alarm cue for fish of different age/size classes may be: (1) identical and that there may be other chemical(s) that allow the test fish to distinguish between cues from fish of different ages/sizes, or (2) the cues are not identical, but similar enough to be recognized.