Effects of brood parasitism on host reproductive success: evidence from larval interactions among dung beetles

This paper investigates the effect of brood parasitism in a dung beetle assemblage in an arid region of Spain. The study was conducted during the spring season (March-May 1994-1998) using mesh cylinders buried into the ground, filled with sand and with sheep dung on top. We quantified the proportion of nests containing larvae of parasitic beetles and their effect on host larvae survival. Experiments on the effect of parasitic larvae on host-larvae survival were conducted by placing scarab brood masses (raised from captive scarabs in the laboratory) in containers with and without aphodiid larvae. During the spring, dung desiccation is rapid, preventing aphodiids nesting in the dung, and forcing these species to adopt brood parasitism as a nesting strategy. Parasitic aphodiids were found in 12-47% of scarab nests of three species. The incidence of brood parasitization was positively related with the number of brood masses contained in the nests, being also higher in the most abundant species. Field data and experiments showed that brood parasites significantly reduced host larvae survival from 74.8% in non-parasitized nests to 8.8% in parasitized nests. Because different rates of nest parasitization and mortality were caused by parasites, brood parasitism had a differential effect on different host species. Thus, brood parasitism constitutes an important mortality factor reducing the reproductive success of the host species and potentially affecting the beetle abundance in the area.     

A comparison of the energy budgets of three species of Pogonomyrmex harvester ants (Hymenoptera: Formicidae)

Summary This investigation compares the energy budgets of three species of Pogonomyrmex harvester ants along an altitudinal transect in southern California. All three demonstrate similar seasonal patterns, with high foraging activity and high respiratory costs in mid-summer and little or no activity during winter. Respiration, predominantely metabolism of the workers, was estimated to account for 84–92% of the energy assimilated by the nests. The remaining 8–16% of the energy was invested in the production of new individuals. However, total production was not correlated with food input. It is suggested that worker care of the brood may be the most important determinant of brood production, and thus food may not be a direct limiting resource in harvester ants.A higher percentage of production is invested in workers than in reproductives in all three species. The species usually partition similar proportions of energy between the production of males and females, but since females are larger, more males are produced. Although the species are in different habitats and have very different numbers of workers per nest, the numbers of sexuals produced per nest are similar. The sex-ratio appears to be ecologically determined. Nests that were provided with additional food invested more energy in the production of males. Control nests, nests which had food removed and older nests invested more in the production of females or invested equally in the production of the two sexes.     

Does ant predation favour leaf beetle specialization on toxic host plants?

Generalist predators are frequently seen as evolutionary forces that narrow the host range in herbivorous insects. Predators may favour specialization of herbivores on host plants containing toxic chemicals (which can be used by herbivores for their own defence) if host plant‐derived defences provide better protection from enemies than do autogenously produced defences. We compared the effectiveness of these two defensive strategies in the larvae of six species of leaf beetle (Chrysomelidae) against wood ants (Formica rufa group) in field experiments. Ants were more strongly repelled by larvae with host plant‐derived, salicylaldehyde‐containing secretions than by larvae with various autogenous secretions, but collectively foraging ants ultimately overcame any type of chemical defence by social interactions, chemical signalling, and olfactory learning. As a result, ants killed all larvae of Chrysomela lapponica defended by salicylaldehyde‐containing secretions within 2 days of their introduction to willows within 15 m of ant nests. We conclude that in the field neither type of chemical defence provides complete protection against wood ants in the vicinity of their nests, and that evolutionary shifts from autogenous production of secretion to sequestration of plant allelochemicals in leaf beetles may be favoured mostly at low ant densities on the periphery of ant foraging areas.     

Colony characteristics influence the risk of nest predation of a polydomous ant by a monotreme

Although predation of individual social insect workers has little effect on colony fitness, nest predation may be a significant selective agent because it can result in substantial loss of reproductive success. Surprisingly, the consequences of predation on social insect nests are poorly understood. In the present study, we investigate the factors that correlate with the probability of predation by echidnas, Tachyglossus aculeatus , on nests and colonies of the facultatively polydomous meat ant, Iridomyrmex purpureus. In particular, we investigate whether colony fragmentation provides a mechanism for reducing the costs of echidna predation. Over 2 years, 138 of the 140 colonies on our study site were depredated. Nest predation was most common in woodlands but with no obvious seasonal patterns. The probability of nest predation was positively correlated with the size of the nest, and negatively correlated with the density of surrounding nests. Although polydomous colonies are at a similar risk of predation by echidnas, the proportion of depredated nests is negatively correlated with the number of nests; thus, the probability that one or more nests avoid predation is increased with increasing nest numbers. Surprisingly, we found no influence of the level of echidna predation on colony growth, measured by either changes in the number of nests or the number of nest entrance holes.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 1–8.     

Meat‐eating enhances larval development of Anthracophora rusticola Burmeister (Coleoptera: Scarabaeidae), which breeds in bird nests

The scarab beetle Anthracophora rusticola Burmeister breeds in the nests of carnivorous birds including the honey buzzard Pernis apivorus (Linnaeus), Chinese goshawk Accipiter soloensis (Horsfield), oriental stork Ciconia boyciana Swinhoe and great cormorant Phalacrocorax carbo (Linnaeus). Although larvae of the beetle probably feed on animal matter (e.g. remnants of birds' food) in the nests of these birds, the effect of eating flesh on the growth of larvae has not been investigated. Laboratory experiments clearly showed that the development was faster, survival rate higher and body heavier just before pupation in larvae fed dried chicken meat with humus soil than in those fed only humus soil. We also investigated feeding behaviors of larvae of the beetle. A piece of chicken meat placed on the surface of humus soil was pulled under the soil by the larva, mostly at night. Video recordings made during the night showed that larvae came to the humus soil surface and ate the dried chicken meat or tried to take the meat under the soil. Our laboratory observations suggest that larvae in nature stay under the humus accumulated in bird nests during the daytime, and then come up to the surface mostly at night to actively seek and eat remnants of the birds' food.     

Ecological characterization of Steinernema scarabaei,a scarab-adapted entomopathogenic nematode from New Jersey

This study describes the basic ecological characteristics of the entomopathogenic nematode Steinernema scarabaei (Rhabditida: Steinernematidae) that was originally isolated from epizootics in scarab populations in New Jersey turfgrass areas. Under laboratory conditions, S. scarabaei infected a limited range of insect species and appeared best adapted to scarab larvae as hosts. It uses a widely ranging foraging strategy with a low attachment rate to mobile hosts on the soil surface but with excellent infection of sedentary host placed at >or=2 cm soil depth. It has a wide thermal activity range with optimum infectivity from 17.5 to 25 degrees C. Because of its foraging strategy and adaptation to scarab larvae as hosts, S. scarabaei has outstanding potential for the control of scarab pests.     

Patterns in foraging and nesting ecology in the neotropical ant, <Emphasis Type="Italic">Gnamptogenys moelleri</Emphasis> (Formicidae,Ponerinae)

Summary This study provides quantitative field data on the natural history and foraging behaviour of the Neotropical bromeliad-nesting ant Gnamptogenys moelleri (Ponerinae) in a sandy plain forest in Southeast Brazil. The ant nested on different bromeliad species and the nests were more frequently found in bigger bromeliads. The species used a wide array of invertebrates in its diet, hunting for live prey and scavenging the majority of the items from dead animals. The food items varied greatly in size (1 to 26 mm). Hunting was always performed by solitary workers. Retrieving was performed by solitary workers (small items), or by a group of 3 to 12 workers recruited to the food source (large items). Almost all G. moelleri foraging activity was restricted to the nest bromeliad. In the warm period more ants left the nest to forage, and foraging trips achieved greater distances compared to the cool season. Trap data revealed that overall availability of arthropod prey is higher in the summer than in the winter. The opportunism in nest site use and in foraging behaviour, the small foraging area, as well as the seasonal differences in foraging activity are discussed and compared with other tropical ants.Received 30 May 2003; revised 22 September 2003; accepted 3 October 2003.     

Genetic diversity of termite-egg mimicking fungi “termite balls” within the nests of termites

Antagonistic or mutualistic interactions between insects and fungi are well-known, and the mutualistic interactions of fungus-growing ants, fungus-growing termites, and fungus-gardening beetles with their respective fungal mutualists are model examples of coevolution. However, our understanding of coevolutionary interactions between insects and fungi has been based on a few model systems. Fungal mimicry of termite eggs is one of the most striking evolutionary consequences of insect–fungus associations. This novel termite–fungus interaction is a good model system to compare with the relatively well-studied systems of fungus-growing ants and termites because termite egg-mimicking fungi are protected in the nests of social insects, as are fungi cultivated by fungus-growing ants and termites. Recently, among systems of fungus-growing ants and termites, much attention has been focused on common factors including monoculture system for the ultimate evolutionary stability of mutualism. We examined the genetic diversity of termite egg-mimicking fungi within host termite nests. RFLP analysis demonstrated that termite nests were often infected by multiple strains of termite egg-mimicking fungi, in contrast to single-strain monocultures in fungus combs of fungus-growing ants and termites. Additionally, phylogenetic analyses indicated the existence of a free-living stage of the termite egg-mimicking fungus as well as frequent long-distance gene flow by spores and subsequent horizontal transmission. Comparisons of these results with previous studies of fungus-growing ants and termites suggest that the level of genetic diversity of fungal symbionts within social insect nests may be important in shaping the outcome of the coevolutionary interaction, despite the fact that the mechanism for achieving genetic diversity varies with the evolutionary histories of the component species.     

The influence of climate on patterns of termite eating in Australian mammals and lizards

Abstract The present paper examines patterns of termite eating in Australian mammals and lizards (total numbers of species, volume percentage of diet) relative to climate (arid, semi-arid, temperate-mesic). Most termite eaters in arid and semi-arid Australia are lizards. Termite consumptio as a proportion of total lizard diet decreases from arid to mesic climates. More mammal species are relatively termite specialized (>50%) in arid than in semi-arid and mesic regions. Termite consumption in echidnas resembles that of the lizards: relatively high in the arid and relatively low in the mesic zone. For the Dasyuridae, termites comprise only a minor fraction (< 10%) in their diet, irrespective of climate. It is argued that the climatic peculiarities of inland Australia (scant and variable rainfall) cause marked seasonality in termite availability, supporting specialized termite eaters in only the most energy-frugal forms (lizards, echidnas). Areas of future research are identified.     

Behavioral Interactions Between <Emphasis Type="Italic">Aphaenogaster rudis</Emphasis> (Hymenoptera: Formicidae) and <Emphasis Type="Italic">Reticulitermes flavipes</Emphasis> (Isoptera: Rhinotermitidae): The Importance of Physical Barriers

Predation pressure from ants is a major driving force in the adaptive evolution of termite defense strategies and termites have evolved elaborate chemical and physical defenses to protect themselves against ants. We examined predator–prey interactions between the woodland ant, Aphaenogaster rudis (Emery) and the eastern subterranean termite, Reticulitermes flavipes (Kollar), two sympatric species widely distributed throughout deciduous forests in eastern North America. To examine the behavioral interactions between A. rudis and R. flavipes we used a series of laboratory behavioral assays and predation experiments where A. rudis and R. flavipes could interact individually or in groups. One-on-one aggression tests revealed that R. flavipes are vulnerable to predation by A. rudis when individual termite workers or soldiers are exposed to ant attacks in open dishes and 100% of termite workers and soldiers died, even though the soldiers were significantly more aggressive towards the ants. The results of predation experiments where larger ant and termite colony fragments interacted provide experimental evidence for the importance of physical barriers for termite colony defense. In experiments where the termites nested within artificial nests (sand-filled containers), A. rudis was aggressive at invading termite nests and inflicted 100% mortality on the termites. In contrast, termite mortality was comparable to controls when termite colonies nested in natural nests comprised of wood blocks. Our results highlight the importance of physical barriers in termite colony defense and suggest that under natural field conditions termites may be less susceptible to attacks by ants when they nest in solid wood, which may offer more structural protection than sand alone.     

Demographic consequences of prey availability and diet of Red-billed Choughs Pyrrhocorax pyrrhocorax

Capsule Variation in prey availability appears to influence Chough fledging success and juvenile survival.

Aims To determine seasonal and annual variations in Chough prey and how these influence fledging success and juvenile survival.

Methods Chough faeces (n = 437, 3905 invertebrates) were collected year-round and analysed to determine diet composition. Seasonal and annual variation in prey abundance in Chough foraging habitat was assessed using pitfall trapping (n = 747, 27 124 invertebrates) between 1996 and 2003. Fledging success was estimated for a population of 12 breeding pairs; juvenile survival was estimated by year-round resighting (n < 2500) of individual birds that were colour-ringed as nestlings.

Results From April to June a high biomass of prey and a great variety of species were observed. Between July and October, both biomass and species diversity were reduced; prey consisted mainly of ants and a few beetle species. From November to March, biomass availability was intermediate, with the diet consisting mostly of Tipulidae larvae, plants and dung beetles. Chough juvenile monthly survival was low in August, November and December. Annual variation in fledging success was correlated with prey biomass availability in May.

Conclusion Seasonal variation in the availability of prey species and their biomass influences Chough demography.     

Temporal Variation in Insect-eating by Chimpanzees and Gorillas in Southeast Cameroon: Extension of Niche Differentiation

I studied insect-foraging strategies of great apes and aimed to define niche differentiation in their insect diet. I investigated seasonality in fruit-, foliage-, insect-, and meat-eating by great apes in southeast Cameroon via indirect methods and measured activity and nest densities of insect prey. I used a multinomial logistic regression to analyze the data. Gorilla and chimpanzee insect-, ant-, and termite-eating does not correlate with rainfall. Ant- and nonwinged termite-eating by chimpanzees increased in periods of succulent fruit scarcity and provided protein and energy, which might have compensated for the protein-low foliage eaten then. The apes ate winged termites when succulent fruit was abundant. Ant and winged termite consumption by gorillas correlates positively with that of chimpanzees. Ant-eating by gorillas increased when fruit was scarce, but was also associated with temporal ant activity and nest density. Both ape species also encountered more ant nests and trails in that period, as they predominantly foraged for herbs in vegetation types with high ant availability. In contrast, fruit-eating correlates positively with nonwinged termite-eating by gorillas, but again temporal prey availability is also associated. Termites might have provided 1) supplemental iron when tannin-rich fruits were eaten or 2) antidiarrheal properties when gorillas ate too much laxative fruit. Termite-eating by both ape species is not associated with spatial termite availability. In conclusion, there is niche differentiation in their insect diet. Based on the trade-off between foraging effort and nutritional gain, chimpanzees use a high-energy and gorillas a low-energy strategy when feeding on termites, but both use a low-energy strategy when feeding on ants. However, more information on the consumption of ant larvae is necessary to define niche differentiation in their ant diet.     

Overwintering ecology of <Emphasis Type="Italic">Philonthus rotundicollis</Emphasis> (Coleoptera,Staphylinidae) in the nest of the carpenter ant <Emphasis Type="Italic">Camponotus herculeanus</Emphasis> on the coast of the Sea of Okhotsk

A widespread rove beetle species, Philonthus rotundicollis, whose distribution range stretches across different climatic zones, including the coldest regions of the Asian northeast, was discovered as an inquiline within the nests of the carpenter ant Camponotus herculeanus on the coast of the Sea of Okhotsk in winter. It remained unclear if the beetles had significant cold-hardiness and whether they overwintered deep in the soil or were confined to particularly warm habitats. To clarify these aspects, the following metrics of cold-hardiness were measured: supercooling point (SCP), freezing point (FP), supercooling capacity (SCP-FP), and temperature minima at the beetles’ overwintering sites. In Ph. rotundicollis, mean SCP was -11.1 ± 0.7°C (ranging from - 7.9 to -18.8°C, n + 15), which was insufficient for successful overwintering even on the coast, since temperature minima in leaf litter during a snow-deficient winter fell to -14°C at the depth of 5 cm and -12°C at 20 cm. The beetles could not burrow deep into stiff soil and made use of crevices in dry peat-like soil layers as well as tunnels of soil- and rootdwelling animals, including carpenter ants. The presence of this rove beetle species in the ant nest was probably due to feeding on ant larvae because, at near-zero temperatures, the activity threshold of the beetles was lower than that of the ants that guarded the larvae.     

Assessment of reproductive status in male echidnas

This study reports the development and application of techniques to assess the reproductive status of male echidnas. The pattern of testosterone secretion over a 24-h period in five echidnas was documented. Testosterone secretion after injection i.m. of either 1000 IU hCG (n=4) or 4 microg GnRH agonist (n=6) was determined to establish whether this could be used as a practical index of the prevailing steroidogenic capacity of the testes. hCG (1000 IU) was also used to assess seasonal changes in testosterone secretion in six echidnas over a 13-month period. Seasonal changes in testicular volume were examined by transabdominal ultrasonography. Electroejaculation was attempted to monitor seasonal changes in sperm production, which was also determined by spermatorrhea. There was no apparent diurnal pattern of testosterone secretion in echidnas and circulating concentrations of testosterone remained relatively low (maximum 1.2 ng/mL) and stable over 24h. Injection of hCG resulted in an increase (P<0.01; n=4) in testosterone concentration with a peak (2.9+/-0.3 ng/mL) approximately 4h after injection. GnRH also induced an increase (P<0.01; n=6) in circulating testosterone that was apparent after 1h (2.6+/-0.3 ng/mL) and concentrations remained elevated (3.4+/-0.3 ng/mL) for up to 8h after injection. Seasonal changes in testosterone secretion determined after injection of hCG, increased (P=0.03; n=6) from late-autumn, peaked in late-winter, and decreased by early-spring. Testicular volume followed a similar seasonal pattern (P<0.01; n=6) with an increase from late-autumn, peak in winter and a decline in mid-spring. There was no seasonal change in live weight. Electroejaculation was attempted throughout two breeding seasons but no semen was obtained. Spermatorrhoea in the echidna was described for the first time and was subsequently used to assess seasonal sperm production. Spermatozoa were found in the urine from June to September. This study has demonstrated that exogenous hormones can be used to obtain an index of the prevailing steroidogenic capacity of the testes in echidnas, which is not apparent with repetitive non-stimulated samples over 24 h. The assessment of testosterone secretion after injection of trophic hormones provides a valuable and practical procedure for the assessment of reproductive status. Testicular ultrasonography and spermatorrhea are useful in assessing reproductive status and in this study were successfully used to determine seasonal reproduction in captive echidnas.     

Excavated substrate modulates growth instability during nest building in ants

In social insects, the nests of the same species can show a large difference in size and shape. Despite these large variations, the nests share the same substructures, some appearing during nest growth. In ants, the interplay between nest size and digging activity leads to two successive morphological transitions from circular to branched shapes (budding along the perimeter of the circular cavity and tunnelling of the galleries). Like several other self-organized collective behaviours, this phenomenon, as well as the entire nest-digging process, is thought to be modulated by environmental properties. The present study investigates the effect of excavated substrate on the nest morphogenesis and the morphological transitions by using two materials with different cohesions. Here, we show that the two morphological transitions occur more frequently with a cohesive substrate than with a granular one: 96 per cent of cohesive experiments showed both transitions, whereas only 50 per cent did in granular experiments. We found that transitions and excavation cessation follow area–response thresholds: the shape transitions take place and the digging activity stops when the dug area reaches the corresponding threshold values. The shape transition thresholds are lower with the cohesive substrate and that of stopping digging is independent of nest shape and material. According to simulations, the experimental frequencies of transitions found their origin in the competition between transitions and activity cessation and in the difference between the transition threshold values of each substrate. Our results demonstrate how the substrate properties modulate the collective response and lead to various patterns. Considering the non-specific mechanisms at work, such effects of substrate coarseness have their counterparts in various collective behaviours, generating alternative patterns to colonize and exploit the environment.     

Larvae of Maculinea rebeli, a large-blue butterfly, and their Myrmica host ants: wild adoption and behaviour in ant-nests

The behavioural interactions between caterpillars of Maculinea rebeli Hir. and their Myrmica ant hosts were studied, both in the wild at the time of adoption, and inside captive nests of six Myrmica species.
In the wild, freshly moulted, final instar caterpillars left their food-plants at a time of day that coincided with the peak foraging activity of Myrmica (18:00-20:00 h). Once on the ground, caterpillars made no attempt to search for Myrmica but settled and waited for foraging ants to find them, which took up to 1.5 h. There was no adoption ritual: foragers of any Myrmica species picked up the caterpillars within 1–4 sec of discovery, and carried them directly to their nests.
Caterpillars grew from < 2 mg to 110 mg in laboratory ant-nests. About 60 mg was gained in autumn but 40% of this was lost during the winter, while the temperature was < 14 °C. Although caterpillars survived best with their normal host, Myrmica schencki , they could also survive in the nests of other Myrmica species. The presence of queen ants had no effect upon survival. The behaviour of the caterpillars was described and illustrated: this included the production of secretions that were drunk by the ants, begging for food and direct feeding by ants. The preferred solid food was ant eggs.
The results are discussed in terms of the social biology of Myrmica ants. It is hypothesized that Maculinea rebeli caterpillars mimic the touch pheromones of ant worker-larvae. This would explain the inability of ants to recognize caterpillars before touching them, their immediate adoption by any Myrmica species after discovery, host specificity inside wild ant-nests, the absence of queen-effect and the intimate attention of host workers.     

Predation by Australian magpies (Gymnorhina tibicen) on pasture invertebrates: Are non-territorial birds less successful?

Diet composition and prey intake rates of Australian magpies in a New Zealand population were investigated to determine whether flocking, non-territorial birds were less successful predators of pasture invertebrates than territorial birds. Time-activity budgets showed that flock magpies foraged throughout the day during February and March, indicative of a prey shortage at that time. Prey abundance was therefore measured in the autumn months but there was no evidence of a large quantitative difference in the food supply of flock and territorial magpies. Significantly fewer invertebrates were collected from pitfall traps in the flock foraging area, but these were counterbalanced by significantly more scarab beetle larvae and more flying insects, obtained by sweep-netting. When compared with territorial magpies, flock birds exhibited similar peck rates, prey intake rates, and earthworm intake rates. While there were qualitative differences in the diets of flock and territorial magpies, determined by faecal analysis, five of seven prey items analysed were captured in the same relative proportions by the flock and territorial birds. Earthworms exceeded their relative availability in the diets of flock birds, and more scarab larvae were found in the diets of territorial magpies. Non-territorial magpies were therefore no less successful than territorial birds during the autumn, and it is suggested that the function of flocking behaviour may eventually be discovered through consideration of why non-territorial birds never occur as solitary individuals, rather than emphasizing comparisons with territorial magpies.     

Community interactions between ants and arboreal-nesting termites in New Guinea coconut plantations

Summary: We investigated the incidence of inquiline ants and of arboreal-nesting ants on a community of three arboreal-nesting termites living in New Guinea coconut plantations. Inquiline ants were present in 10 % of Microcerotermes biroi nests and in 4 % of Nasutitermes princeps nests. Live termite nests inhabited by the most common inquiline ant, Camponotus sp. A, were generally left by the ant after several months. In some nests, Camponotus sp. A was observed coexisting with its host during the whole observation period (3 years). Therefore, Camponotus sp. A was apparently an opportunistic inquiline which did not affect significantly the mortality of termite colonies. The arboreal-nesting ant, Crematogaster irritabilis, was locally found occupying up to 99 % of the trees present in 1 ha plots. In such hot spots, the overall abundance of termites was approximately half that of plots devoid of Crematogaster irritabilis. The high density of Crematogaster irritabilis may be an important limiting factor for the termite assemblage, by hastening the death or hindering the establishment of arboreal termite colonies.     

Resource density regulates the foraging investment in higher termite species

1. Resource density can regulate the area that animals use. At low resource density, there is a conflict in terms of balance between costs of foraging and benefits acquired. The foraging of the higher termite Nasutitermes aff. coxipoensis consists of searching throughout trails and a building galleries phase. 2. In this study, a manipulative field experiment was used to test the hypothesis that colonies of N. aff. coxipoensis forage towards a more profitable balance between the establishment of trails and gallery construction at low resource density. 3. The experiment was conducted in north‐eastern Brazil. Seven experimental plots were established with a continuous increase in resource density (sugarcane baits). Entire colonies of N. aff. coxipoensis were transplanted from their original sites to the experimental plot, totalling 35 nests. The number, branches and total length of trails and galleries were quantified. 4. The results show that N. aff. coxipoensis optimises its foraging output, intensifying the establishment of trails at the cost of gallery construction when resource density is low. The number of trails, the number of trail branches and the total length of trails decreased with increasing resource density. Interestingly, at low resource density, the search effort was concentrated on forming longer and a greater number of trails, a small proportion of which were converted into galleries. The opposite relationship was observed at high resource density. 5. These results suggest an optimisation of search efforts during foraging depending on resource density, a mechanism that may help researchers to understand the use of space by higher termite species.     

Effectiveness of protein-rich pea flour for the control of stored-product beetles

Abstract The association between visiting ants and the extrafloral nectaries (EFN)‐bearing shrub Hibiscus pernambucensis Arruda (Malvaceae) was investigated in two different coastal habitats – a permanently dry sandy forest and a regularly inundated mangrove forest. In both habitats the frequency of plants with ants and the mean number of ants per plant were much higher on H. pernambucensis than on non‐nectariferous neighbouring plants. In the sandy forest the proportion of live termite baits attacked by ants on H. pernambucensis was much higher than on plants lacking EFNs. In the mangrove, however, ants attacked equal numbers of termites on either plant class. Ant attendance to tuna/honey baits revealed that overall ant activity in the sandy forest is higher than in the mangrove area. The vertical distribution (ground vs. foliage) of ant activity also differed between habitats. While in the mangrove foraging ants were more frequent at baits placed on foliage, in the sandy forest ant attendance was higher at ground baits. Plants housing ant colonies were more common in the mangrove than in the sandy forest. Frequent flooding in the mangrove may have resulted in increased numbers of ant nests on vegetation and scattered ant activity across plant foliage, irrespective of possession of EFNs. Thus plants with EFNs in the mangrove may not experience increased ant aggression towards potential herbivores relative to plants lacking EFNs. The study suggests that the vertical distribution of ant activity, as related to different nest site distribution (ground vs. foliage) through a spatial scale, can mediate ant foraging patterns on plant foliage and probably affect the ants’ potential for herbivore deterrence on an EFN‐bearing plant species.