0000000000314659
AUTHOR
Daniela Lo Giudice
Plant surfaces of vegetable crops mediate interactions between chemical footprints of true bugs and their egg parasitoids.
During the host location process, egg parasitoids can eavesdrop on chemical cues released from immature and adult hosts. These indirect host-related cues are highly detectable, but of low reliability because they lead egg parasitoid females to an area where oviposition is likely to occur rather then providing wasps with direct information on the presence of eggs and their location. In the host-parasitoid associations between true bugs and their scelionid egg parasitoids, female wasps perceive the chemical residues left by host adults walking on substrates as contact kairomones, displaying a characteristic arrestment posture. In this study, we demonstrated that epicuticular waxes of leaves o…
Plant surface mediates interaction between true bug chemical footprints and scelionid egg parasitoids
Chemical footprints left behind by true bugs act as contact kairomones inducing an arrestment response in scelionid egg parasitoids. Once in contact with contaminated substrates, female wasps display a characteristic arrestment posture followed by an increase of the host searching time. Previous studies were conducted on artificial substrates as filter papers, so that little is known about the effects of natural substrates on behavioural response by wasps. In field, the substrate where these interactions occur, i.e. the surface of plants, is covered by wax layers that can have a role in trophic interactions between insects. In this study, we investigated the influence of plant surfaces on a…
Individuazione di un feromone sessuale marcante traccia nell’imenottero parassitoide Metaphycus luteolus
Metaphycus luteolus Timberlake (Hymenoptera: Encyrtidae) è un parassitoide gregario facolativo di Coccidi (Homoptera: Coccidae). Nel presente studio, si è indagato sull’esistenza in questa specie di un feromone che potesse guidare l’incontro fra i sessi nei siti di emergenza. In altri imenotteri calcidoidei, parassitoidi di ospiti che vivono in dense aggregazioni come colonie di cocciniglie o afidi, l’incontro fra i sessi nei siti di emergenza è mediato da feromoni a corto raggio. Il presente studio mette in evidenza l’esistenza di un feromone di traccia in M. luteolus. I biosaggi sono stati eseguiti con l’ausilio di un’arena aperta, costituita da una piastra di vetro, sulla quale sono stat…
Chemo-orientation responses in hymenopteran parasitoids induced by substrate-borne semiochemicals
Hymenopteran parasitoids can utilize substrate-borne semiochemicals released by conspecifics or by their hosts, increasing the likelihood of successful mating and host location. According to the literature, two substrate-borne chemo-orientation patterns can occur: (1) biased random searching, a non-directional reaction toward the chemicals (kinesis), and (2) trailfollowing searching, a directional response toward the source emitting the chemical compounds (taxis). These two different strategies can be adopted by parasitoids to locate hosts and mates. In host location, random searching is induced by allelochemicals indirectly associated with the host, whereas trail-following behavior is indu…
Biology and behavior of Metaphycus angustifrons Compere (Hymenoptera: Encyrtidae), a newly discovered parasitoid of soft scale insects (Hemiptera: Coccidae) in California
Abstract Metaphycus angustifrons Compere has recently been found to be the most abundant parasitoid of brown soft scale, Coccus hesperidum L., in southern California. In laboratory experiments we examined several biological parameters of this species. M. angustifrons both oviposits and host feeds in brown soft scale and is a facultatively gregarious endoparasitoid of this soft scale insect. In contrast with other Metaphycus spp., M. angustifrons is a koinobiont parasitoid, allowing its host to grow up to 40% beyond its size at parasitism. Despite its high abundance on brown soft scale in the field, in the laboratory, high rates of parasitoid egg encapsulation are observed; about half of par…
Host sex discrimination by an egg parasitoid on Brassica leaves.
Egg parasitoids are able to find their hosts by exploiting their chemical footprints as host location cues. In nature, the apolar epicuticular wax layer of plants that consists of several classes of hydrocarbons serves as the substrate that retains these contact kairomones. However, experiments on chemical footprints generally have used filter paper as substrate to study insect behavior. Here, we explored the ability of Trissolcus basalis (Scelionidae) females to discriminate between footprint cues left by male and female Nezara viridula (Pentatomidae) on leaves of their host plant Brassica oleracea (broccoli). Furthermore, we analyzed the chemical composition of the outermost wax layer of …
Leaf epicuticular waxes effects egg parasitoid’s response to host adult footprint contact kairomone
Chemical footprints left behind by true bugs are perceived as a contact kairomones by scelionid egg parasitoids. In the system Nezara viridula and its egg parasitoid Trissolcus basalis, previous studies have shown that the kairomone mediating such behavior is part of N. viridula’s cuticular hydrocarbons. In this study, the effect of epicuticular waxes of leaves of broad bean, Vicia faba, on wasp response to footprints of N. viridula females are investigated. Plants with intact waxes layer were used (1) without host chemical contamination, or (2) contaminated by host female footprints. Mechanically de-waxed plants were tested (3) without host chemical contamination, or (4) de-waxed a few min…
L’orientamento guidato da semiochimici di contatto in imenotteri parassitoidi
Il Chemio-orientamento negli imenotteri parassitoidi e più genericamente negli insetti, si manifesta con movimenti nel tempo e nello spazio guidati da informazioni chimiche a differente grado di volatilità. Nel caso dei semiochimici di contatto, la ricezione è affidata a sensilli gustativi uni e multiporo e si manifesta con un periodo di immobilità, durante il quale le antenne vengono mantenute aderenti alla superficie esaminata. Successivamente si possono, generalmente, distinguere due tipi di comportamento: ricerca random e ricerca direzionale. La ricerca random è caratterizzata da un decremento della velocità lineare di locomozione e da un incremento della velocità angolare, in tal modo …
La localizzazione dell’ospite nei parassitoidi oofagi: il ruolo delle cere epicuticolari delle piante
La localizzazione dell’ospite nei parassitoidi oofagi è il risultato di un complesso comportamento di foraggiamento influenzato prevalentemente da stimoli di natura fisica e chimica. I segnali chimici (semiochimici) possono derivare dall’interazione tra la pianta e l’uovo ospite (sinomoni indotti dall’ovideposizione), dall’uovo tal quale (cairomoni diretti) e/o da stadi diversi da quello di uovo, come per esempio l’adulto (cairomoni indiretti). I sinomoni indotti con l’ovideposizione, capaci di richiamare i parassitoidi delle uova ancor prima che il fitofago possa causare danni, sono un efficace esempio del coinvolgimento “diretto” della pianta nel processo di localizzazione dell’ospite da …
Emergence, dispersal, and mate finding via a substrate-borne sex pheromone in the parasitoidMetaphycus luteolus
Metaphycus luteolus Timberlake (Hymenoptera: Encyrtidae) is a facultatively gregarious parasitoid of soft scale insects. We conducted behavioral experiments to better understand the mating structure of this species. Emergence of male and female offspring is synchronized, beginning at the onset of photoperiod. Both sexes are able to disperse, although dispersal of males from natal patches appears to take longer than dispersal of females. We demonstrated the presence of a female-produced contact pheromone using open arena bioassays and motion tracking software, testing residues deposited by walking females, and extracts of females. Males responded to the females' chemical footprints' and to a…
The response of Trissolcus basalis to footprint contact kairomones from Nezara viridula females is mediated by leaf epicuticular waxes.
Chemical footprints left behind by true bugs are perceived as contact kairomones by scelionid egg parasitoids. Female wasps encountering a contaminated artificial substrate display a characteristic arrestment posture, holding the body motionless and antennating the surface. In the system Nezara viridula (L.) and its egg parasitoid Trissolcus basalis (Wollaston), previous studies have shown that the kairomone mediating such behavior is part of N. viridula's cuticular hydrocarbons (CHC) and furthermore that the wasp's ability to discriminate host male and female footprints is mainly based on the presence/absence of nonadecane (nC(19)). In this study, the effect of epicuticular waxes of leaves…