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We investigated the behavioral responses of the Asian citrus psyllid, Diaphorina citri , to the trail of the convergent ladybird beetle, Hippodamia convergens. We tested the hypothesis that H. convergens trails reduce D. citri host acceptance using choice tests. Citrus plants previously exposed to ladybird beetle larvae and adult trails were avoided by D. citri compared to untreated controls. Female D. citri settling on H. convergens -exposed plants decreased as the density of ladybird beetle larvae or adults used to expose treatment plants was increased. Larval and adult trails were equally repellent to D. citri . In laboratory olfactometer assays that measured orientation to volatile chemical cues, D. citri females avoided citrus plants that were pre-exposed to caged H. convergens larvae for 1, 5 or 10 days as compared with non-exposed controls. Diaphorina citri did not avoid the odor of citrus plants pre-exposed to caged adult H. convergens for 1 or 5 days as compared with the control. However, more female D. citri chose untreated control arms as compared with plants exposed to H. convergens adults for 10 days. We collected larval trails deposited by H. convergens and mechanically re-applied them to citrus plants as a spray solution. D. citri significantly avoided plants treated with previously collected H. convergens trail solutions in choice tests as compared with untreated controls; treatments caused 15 days of residual behavioral activity on D. citri . Our results indicate that chemical cues mediate avoidance of ladybird beetle trails by D. citri . Implications for biological and non-insecticidal control of D. citri are discussed. [ABSTRACT FROM AUTHOR]

The effects of the larval tracks of Episyrphus balteatus DeGeer (Diptera: Syrphidae) and Harmonia axyridis Pallas (Coleoptera: Coccinellidae) on the egg laying behavior of females of the predatory hoverfly E. balteatus were investigated in two-choice experiments. The oviposition response of H. axyridis to larval tracks of E. balteatus was also tested in one-choice experiments. Gravid E. balteatus females laid significantly fewer eggs on leaf discs with aphids and contaminated with tracks of conspecific or heterospecific larvae than on control leaf discs. H. axyridis females laid similar numbers of eggs in Petri dishes with aphids and contaminated with the tracks of E. balteatus larvae as in control Petri dishes. This indicates that E. balteatus females lay fewer eggs at sites where there are conspecific and heterospecific larval tracks, whereas the tracks of the syrphid larvae did not deter H. axyridis females from laying eggs.

The oviposition deterring effects of fresh larval tracks of Cheilomenes sexmaculata (F.), Ceratomegilla undecimnotata (Schneider), Cycloneda limbifer Casey, and Harmonia dimidiata (F.) on C. sexmaculata females were compared in standard laboratory choice tests. Moreover, the persistence of intraspecific effects of C. sexmaculata larval tracks were investigated. Fresh tracks of C. sexmaculata, C. limbifer and C. undecimnotata larvae effectively deterred C. sexmaculata females from ovipositing. The effect of fresh larval tracks of H. dimidiata was not statistically significant. The oviposition-deterring effects of 10 d-old conspecific larval tracks were considerably lower than those of fresh tracks, but remained significant. Clutch sizes were smaller in the blank test without larval tracks than in choice tests with fresh tracks of conspecific, C. limbifer, C. undecimnotata, H. dimidiata larvae and with 10 d-old tracks of conspecific larvae. The study indicates that semiochemicals in the tracks of conspecific and heterospecific coccinellid larvae can contribute considerably to the spacing of C. sexmaculata offspring among prey resources of differing quality and that conspecific as well as heterospecific larval tracks can influence clutch size.

The ability of the aphidophagous coccinellids Cycloneda limbifer Casey and Ceratomegilla undecimnotata (Schneider) to discriminate between simultaneously provided clean paper strips and paper strips with oviposition-deterring larval tracks was studied after the ablation of different sense organs. Females oviposited similar numbers of eggs on paper strips with conspecific tracks and on clean paper strips only when deprived of both maxillary palpi. C. undecimnotata without maxillary palpi also did not differentiate between clean paper strips and paper strips with tracks of the coccinellid Leis dimidiata (F.). If both antennae and one maxillary palpus were simultaneously ablated, females of both species laid significantly more eggs on clean than contaminated paper strips. The results of this study indicate that females use contact chemoreceptors on maxillary palpi exclusively to detect oviposition deterring tracks of conspecific larvae.Intact females of C. limbifer laid significantly larger batches of eggs on paper strips with conspecific larval tracks, than on clean paper strips in blank test. In contrast, intact females of C. undecimnotata laid significantly smaller batches on paper strips with conspecific tracks than on clean paper strips in blank test. This is the first evidence of an opposite effect of conspecific oviposition deterring larval tracks on egg clustering in aphidophagous coccinellids.

The persistence of oviposition-deterring effects of coccinellid and chrysopid larval tracks on females of three aphidophagous coccinellid species was compared. One month old tracks of first instars of the coccinellid Cycloneda limbifer Casey deterred conspecific females from oviposition in choice tests with clean and contaminated substrates. Intraspecific effect of larval tracks in Semiadalia undecimnotata Schneider was statistically significant after 10 days. Although fresh tracks of conspecific first instars effectively deterred females in both tested populations of Coccinella septempunctata L., deterrent effects disappeared when tracks of larvae were only one day old. However, females of C. septempunctata laid fewer eggs on sites with 10 days old tracks of Chrysopa oculata Say or sites with one month old tracks of Chrysopa perla (L.) first instars than on clean sites. In contrast to females of C. septempunctata and S. undecimnotata, C. limbifer females left significantly more faecal spots on clean sites than on sites with 5-30 days old tracks of conspecific first instars. This indicates that sites with tracks of larvae can also effectively repel conspecific females of some coccinellid species from searching.

Choice tests showed that tracks left by coccinellid larvae have generally little effect on oviposition site selection by chrysopid females. Fresh tracks of first instar larvae of the coccinellid species Coccinella septempunctata, Cycloneda limbifer, Leis dimidiata and Semiadalia undecimnotata, did not deter females of the chrysopid Chrysopa oculata from laying eggs. Females of Chrysopa perla avoided ovipositing only on substrates with tracks of L. dimidiata larvae.

Larvae of aphidophagous ladybirds leave a cue in their tracks that deters oviposition. The influence of relatedness on this behaviour is for the first time explored in this paper. Two-spot ladybird females (Adalia bipunctata L.) under different conditions (young and naive, young and experienced, and old and naive) were exposed either to (i) clean filter paper, (ii) filter paper contaminated with unrelated larval tracks or (iii) filter paper contaminated with related larval tracks from their offspring. Oviposition time was recorded during nine hours. Oviposition was inhibited by larval tracks, and was more so by related than unrelated ones. Experienced females showed the same behaviour but with lower intensity. With old females, response was not significant with any type of larval tracks. This is the first report of the effect of relatedness on a ladybird's response to larval tracks. [ABSTRACT FROM PUBLISHER]

Cannibalism, where one species feeds on individuals of its own species, and intraguild predation (IGP), where a predator feeds on other predatory species, can both pose significant threats to natural enemies and interfere with their biological control of pests. Behavioral mechanisms to avoid these threats, however, could help maintain superior pest control. Here, we ask whether larvae of Coccinella septempunctata (Coleoptera: Coccinellidae) and Harmonia axyridis (Coleoptera: Coccinellidae) respond to larval tracks deposited by the other and whether this behavioral response reduces the threat of cannibalism and IGP. In petri dish experiments, we show that both H. axyridis and C. septempunctata avoid foraging in areas with conspecific larval tracks. Using a method of preventing larvae from depositing tracks, we then demonstrate that the frequency of cannibalism is greater for both species when larvae are prevented from depositing tracks compared with when the tracks are deposited. For multi-species interactions we show in petri dish experiments that C. septempunctata avoids H. axyridis larval tracks but H. axyridis does not avoid C. septempunctata larval tracks, demonstrating an asymmetry in response to larval tracks that parallels the asymmetry in aggressiveness between these species as intraguild predators. On single plants, we show that the presence of H. axyridis larval tracks reduces the risk of IGP by H. axyridis on C. septempunctata. Our study suggests that larval tracks can be used in more ways than previously described, in this case by changing coccinellid larval behavior in a way that reduces cannibalism and IGP. [ABSTRACT FROM AUTHOR]

Abstract: The food available to coccinellid larvae and their exposure to predation is influenced by where they are placed as eggs. This review examines adult distribution and female oviposition strategies which in turn determine the distribution of coccinellid larvae in habitats. Immigration into a habitat can be influenced by visual and olfactory cues related to habitat quality. Adults are retained in a habitat if sufficient food resources are present. The abundance and quality of food in a habitat affects the reproductive output of a female and survival of larvae. Consequently, there is higher retention and oviposition preference for sites with abundant essential prey. Coccinellids also increase reproduction in response to non-prey foods (i.e., pollen), but avoid ovipositing in areas with copious amounts of honeydew. In laboratory studies, many plant-derived chemicals have been demonstrated to be attractants and oviposition stimulants. The need to place eggs in proximity to food for offspring must be weighed against the risk of cannibalism and intraguild predation. Lady beetles avoid egg predation by reducing oviposition where other adults are present, ovipositing on plants associated with less exposure or incidence of intraguild predation, and avoiding areas with tracks and frass of con- and heterospecific larvae. Indeed, deterrent cues for avoiding predation seem stronger than the positive ones associated with food. An understanding of the resources needed for successful reproduction and larval development in a habitat and the sensory cues that signal these resources, and thus elicit oviposition, may enhance our understanding of the underlying mechanisms affecting coccinellid distribution in habitats. [Copyright &y& Elsevier]

1. Dynamic models of optimal foraging predict that an animal's decision to accept or reject a patch depends not only on the environment and patch quality, but also on its internal state. Previous experiments have shown that the two-spot ladybird beetle,Adalia bipunctata(L.), is reluctant to lay eggs in a patch of prey contaminated by the oviposition-deterring pheromone produced by conspecific larvae.2. An experiment was conducted to test whether the internal state of anA. bipunctatafemale affects its oviposition response to oviposition-deterring pheromone. Firstly, the oviposition response to oviposition-deterring pheromone of young and old females was compared. Secondly, the oviposition response to oviposition-deterring pheromone of females previously exposed continuously to oviposition-deterring pheromone was compared with that of females of the same age but with no previous experience of oviposition-deterring pheromone.3. Old females and females with previous experience of oviposition-deterring pheromone were less reluctant to lay eggs in the presence of oviposition-deterring pheromone than young and naive females. These results are consistent with the predictions of optimal foraging theory. [ABSTRACT FROM AUTHOR]

Gravid females of the two-spot ladybird, Adalia bipunctata (L.), were deterred from ovipositing when kept in petri dishes that had previously contained conspecific larvae but not conspecific adults, or the larvae of another two species of ladybird, Adalia decempunctata (L.) and Coccinella septempunctata L. The deterrent effect was density dependent and mediated via a chloroform-soluble contact pheromone present in the larval tracks. Similarly, gravid females of C. septempunctata were deterred from ovipositing by conspecific larval tracks and chloroform extracts of these tracks, but not by the tracks or extracts of tracks of A. bipunctata larvae. That is, in ladybirds the larvae produce a species-specific oviposition-deterring pheromone. In the field, the incidence of egg cannibalism in ladybirds increases very rapidly with the density of conspecific eggs or larvae per unit area. Thus, in responding to the species specific oviposition deterring pheromone female ladybirds reduce the risk of their eggs being eaten and spread their offspring more equally between patches. [ABSTRACT FROM AUTHOR]