Jean-Paul Lachaud

Graded recruitment and hunting strategies linked to prey weight and size in the ponerine ant Ectatomma ruidum

Abstract According to the weight and size of their prey, Ectatomma ruidum workers can employ different recruitment systems (solitary hunting, cooperative hunting and group hunting with recruitment) when mastering and retrieving prey items from short distances from the nest. Prey size determined the backwards entry typically adopted by this species, while prey weight determined the predatory strategy selected. After a common initial sequence (search for prey, detection, localization), predatory sequences varied in terms of the type of approach, the site of seizure, the reaction after stinging and the type of transport. Nevertheless, irrespective of prey weight and size, seizure was preferentially oriented towards the head and prey were always stung. Short-range recruitment and mass recruitment without trail laying were elicited by a large range of heavy prey (> 2.5 times the weight of an individual worker). According to the mortality risk associated with each prey, hunters exhibited a “prudent” stinging posture associated with an increase in the duration of the subsequent phase of waiting for prey immobilization. The overall time of capture was positively correlated with the weight of the prey. When collective hunting strategies were involved, E. ruidum colonies matched the number of recruited hunters to the size and weight of the prey. Compared to solitary hunting strategies, for short food–nest distances, this graded recruitment appeared to enhance the energetic benefits derived by this species from the use of recruitment systems: the higher the number of workers involved in the recruitment process, the greater the energetic benefits obtained. The exhibition or absence of trail laying behavior in the recruitment responses displayed by E. ruidum workers is discussed in relation to their involvement in scavenging or predatory behavior.

Diversity of Species and Behavior of Hymenopteran Parasitoids of Ants: A Review

Reports of hymenopterans associated with ants involve more than 500 species, but only a fraction unambiguously pertain to actual parasitoids. In this paper, we attempt to provide an overview of both the diversity of these parasitoid wasps and the diversity of the types of interactions they have formed with their ant hosts. The reliable list of parasitoid wasps using ants as primary hosts includes at least 138 species, reported between 1852 and 2011, distributed among 9 families from 3 superfamilies. These parasitoids exhibit a wide array of biologies and developmental strategies: ecto- or endoparasitism, solitary or gregarious, and idio- or koinobiosis. All castes of ants and all developmental stages, excepting eggs, are possible targets. Some species parasitize adult worker ants while foraging or performing other activities outside the nest; however, in most cases, parasitoids attack ant larvae either inside or outside their nests. Based on their abundance and success in attacking ants, some parasitoid wasps like diapriids and eucharitids seem excellent potential models to explore how parasitoids impact ant colony demography, population biology, and ant community structure. Despite a significant increase in our knowledge of hymenopteran parasitoids of ants, most of them remain to be discovered.

Insect gladiators: competitive interactions between three species of bethylid wasps attacking the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae)

The coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae), originates from Africa and has since invaded all major coffee growing areas in the world. The parasitoid species, Cephalonomia stephanoderis Betrem and Prorops nasuta Waterston (Hymenoptera: Bethylidae) have been introduced into many countries as biological control agents. Recently, a further bethylid, Cephalonomia hyalinipennis Ashmead, was found naturally attacking the coffee berry borer in southern Mexico. The biologies of these three species are broadly similar. We evaluate the potential for interspecific competition by observing direct behavioral contests for hosts occurring between adult female parasitoids. We show that such contests readily occur and the loser is frequently killed. Prior ownership of hosts and ovipositional experience influence contest outcome, probably via the dynamics of egg maturation. There are also competitive asymmetries between these species: C. stephanoderis is generally the most successful. We discuss the implications of interspecific competition on the question of the best number and combination of natural enemy species for biological pest control.

Efficiency in the exploitation of patchy environments by the ponerine antPaltothyreus tarsatus: an ecological consequence of the flexibility of prey capture behavior

Paltothyreus tarsatus workers show an adaptive predatory strategy compatible with central place theory which predicts that single-prey loading is an extension of the optimal diet choice while multiple-prey loading behavior would correspond to the optimal use of patches. The insight learning involved in the quick modifications of predatory strategy enablesP. tarsatus to hunt all available prey in a great diversity of sizes and species. Nevertheless, this generalist predator strongly preferred termites and very large prey such as giant diplopods and crickets to other choices within its diet. In the hunting of these favorite prey, the recruitment of nestmates enhanced the efficiency of total predation, though the release of a chemical trail appeared to depend on the hunger-satiety balance of the colony. In addition to the hunger, the miscapture of prey also triggered the release of chemical trails. The strategy for capturing grouped termites was characterized by the loading of multiple prey at a single time, by a concentrated search in a restricted area and by an optional recruitment of nestmates. These behavioral characteristics of ponerine ants probably account for the flexibility of their predatory strategy for hunting aggregated small prey.

Cuticular Hydrocarbons of Kapala sulcifacies (Hymenoptera: Eucharitidae) and Its Host, the Ponerine Ant Ectatomma ruidum (Hymenoptera: Formicidae)

Abstract Cuticular hydrocarbons from the ponerine ant Ectatomma ruidum Roger and a highly integrated eucharitid myrmecophile, Kapala sulcifacies (Cameron), associated with it, have been characterized. Ninety hydrocarbons were identified from the ant, 55 hydrocarbons from the female wasp and 54 hydrocarbons from the male wasp. The wasps and ants share 40 hydrocarbons. These shared 40 hydrocarbons represent 92.6% of their hydrocarbon composition for female Kapala, 84.3% for male Kapala and 67.7% for the ants. The wasps have a carbon number range of C27 to C35; the ants have a range of C23 to C35. Both species possess n-alkanes, C27 to C33 for the wasps, C23 to C34 for the ants. Both species also possess major quantities of Z-7- and Z-9 alkenes: C29 to C33 for the wasps; C23 to C35 for the ants. The female wasps possess a low amount of a conjugated C31 diene (neither the ants nor the male wasps possess this hydrocarbon), and the ants, but not the wasps, contain low quantities of nonconjugated dienes (carbon numbers of C23 to C29) with double bonds at Δ9, and Δ14. Both wasps and ants share homologous series of 3-, 5-, 10-, 11-, 12-, 13-, 15- and 17-methyl branched alkanes. Ants and wasps also share a homologous series of 3,7-dimethyl alkanes. Other internally branched dimethyl alkanes are found in both ants and wasps, but only 11, 15-DiMeC29 is shared. Wasps have 7, 15- and 10, 14-dimethyl alkanes while the ants have 15,19-dimethyl alkanes. Kapala sulcifacies and E. ruidum both possess hydrocarbons of the 5, X-, 11, X-, 12, X- and 13, X-DiMe series, but the compounds involved are not shared because they represent different compounds. Behavioral observations indicate that the ants accept the newly emerged adult parasitoids with no evidence of agonistic behavior for a period of time after adult eclosion. Nevertheless, the chemical deception is not completely efficient because young adult Kapala are soon ejected from the nest by transportation by their host. These transportations frequently occur after seizure at the base of the wasps’ characteristic scutellar spines, such structures allowing for easy transportation without injury for the parasite. Moreover, if no method of escaping the colony is provided, the ants ultimately attack the parasitoids. The substantial chemical overlap of the cuticular hydrocarbon profiles of the ants and wasps are discussed in the context of the social life of the colony.

Ecology and behavior of the seed-eating ponerine antBrachyponera senaarensis (Mayr)

SummaryColonies ofBrachyponera senaarensis, a species known for its adaptation to dry tropical conditions in Sudanes savannas, can also flourish in a wet tropical environment if it is particularly sunny and well-drained, e. g. in sandy regions. The feeding strategy of this species is opportunistic, with great flexibility of nesting, foraging, and diet according to the nature of the environmental constraints. Swarming takes place at the height of the rainy season. Foundation is partially claustral and haplometrotic or, more rarely, pleometrotic. Daily foraging activity of workers, which is mainly diurnal, peaks between 07∶00 h and 09∶00 h and then ceases between 11∶00 h and 14∶00 h. The size of workers varies between colonies, depending on the richness of their environment. Moreover, two worker subcastes may be distinguished in a colony: (1) individuals which are nonpigmented at birth and represent the majority of the worker population; and (2) larger workers, whose level of maturation is more advanced both morphologically and behaviorally, as shown by an age-polyethism study.

Growth-related changes in predation behavior in incipient colonies of the ponerine antEctatomma tuberculatum (Olivier)

SummaryWe traced the development in the laboratory of 18 young colonies of the arboricolous ponerine antEctatomma tuberculatum. Colony foundation is of the partially-claustral type. During the early stages, when the colony is entirely dependent on the queens behavior, the growth of the colony in terms of number of workers produced over time was relatively predictable. Afterwards, divergence in colony growth in function of the time increases as fast as the number of workers influences the efficiency of colony provisioning.Comparative analysis indicated clear changes in the predation behavior of foundresses and workers as colonies developed. For any stage of colony growth, all individuals provisioned the nest with dead prey or sugar-rich substances in the same way. However, prey hunting involves two different strategies. Foundresses and nanitic workers (originating from colonies with 9–15 workers) foraged actively, catching prey as the result of random encounters. Post-nanitic foragers (originating from colonies with 20–30 workers) and those from nature colonies developed an ambush strategy. Workers in these colonies gained experience at catching and handling prey during a period when they acted as nest guards, and so tended to be more efficient hunters than poorly experienced foundresses or nanitic foragers. The change in strategy was also positively correlated with an increase in the size of workers as the colony matured. A stable maximum in workers size is apparently reached only after the appearance of efficiently hunting foragers, presumably in numbers sufficient to provide adequate quantity and quality of larval food. Such a correlation between worker size and colony growth, assumed general for all ants, has not been demonstrated for Ponerinae before this work.

Use of Long-Term Stored Vector Information in the Neotropical Ant Gigantiops destructor

We investigated how the formicine ant Gigantiops destructor can use vector information to navigate within the cluttered environment of the rain forest. Displaced foragers use skylight information to move in the theoretical feeder-to-nest direction, whether they are prevented from updating their path-integrator during foraging or captured at the departure from their nest, i.e. with a current accumulator state very close to zero. Only ants that have collected food are able to download a long-term stored reference vector pointing in the nest direction, irrespective of the current accumulator state of their path-integrator stored in a working memory and independent of familiar landmarks. Depending on the release sites, ants that became lost at a maximum distance of 50 cm could still hit and recognize their familiar route, or they engaged in a systematic search for it centered on the release sites. In contrast to Cataglyphis desert ants, Gigantiops ants do not rely primarily on the current accumulator state of their egocentric path integrator. Such a long-term vector-based navigation primed by food capture is well adapted for a tropical ant foraging during periods spanning several hours. This could prevent the numerous cumulative errors in the evaluation of the angles steered that might result from a continuously running path-integrator operating during complex foraging patterns performed at ground or arboreal levels and during passive displacement in response to heavy rain.

Biology and Behavior of Kapala (Hymenoptera: Eucharitidae) Attacking Ectatomma, Gnamptogenys, and Pachycondyla (Formicidae: Ectatomminae and Ponerinae) in Chiapas, Mexico

Abstract Kapala (Hymenoptera: Eucharitidae) are among the most frequently collected chalcidoid wasps from the Neotropics, but general information about their host plants, behavior, and life history is scarce. A new species, Kapala izapa n. sp., parasitizing Ectatomma ruidum Roger (Hymenoptera: Formicidae), is described from Chiapas, Mexico, with a general account of its biology. Field observations on the behavior of adults of Kapala iridicolor (Cameron), which also attack E. ruidum, Gnamptogenys regularis Mayr, Gnamptogenys sulcata (Fr. Smith), Gnamptogenys striatula Mayr, and Pachycondyla stigma (F.) (Hymenoptera: Formicidae), are included. Immature stages of Kapala izapa n. sp. follow the general morphology and behavior described for other eucharitids known to attack Ectatomminae and Ponerinae. More than one parasitoid can complete development on a single host larva. K. iridicolor females were observed laying masses of eggs on undeveloped flower buds of Melampodium divaricatum (L.C. Richard) D.C. (Asteraceae). Extrafloral nectaries of this plant are visited by several insects, including predatory foraging worker ants of E. ruidum. Dissection of recently emerged females of K. iridicolor yielded ≈4,500 fully developed eggs.

Polyethism within hunters of the ponerine ant, Ectatomma ruidum Roger (Formicidae, Ponerinae)

SummaryDuring laboratory experiments, two categories of prey-foraging workers were found inEctatomma ruidum: stingers and transporters. When numerous live drosophila were offered to the ants, one group of hunters specialized in killing the prey and another in transporting simultaneously the dead drosophila to the nest. Sometimes, there was a transfer of prey by a stinger towards a transporter, after an active soliciting of the transporter by antennation or by using the forelegs. We found high positive correlations between the colony size and the number of ants in each subcaste. A negative correlation existed between the colony size and the proportion of hunters. However, the proportion of workers in the two behavioral subcastes of hunters was stable in spite of differences in colony size. The phylogenetic interest of this type of cooperative predation is discussed.