Ontogenetic shifts in competitive interactions and intra-guild predation between two wolf spider species

Abstract. 1. The wolf spiders (Araneae: Lycosidae) Hogna helluo (Walckenaer) and Pardosa milvina Hentz co-occur in soybean fields of south-west Ohio, U.S.A. As adults, Hogna is the larger species and has the competitive advantage in most interactions; due to differing phenologies, however, their size-classes frequently overlap and as such there is potential for shifts in competitive ability and intra-guild predation. The hypothesis that competitive interactions and intra-guild predation will favour Pardosa when Pardosa is similar-sized, or has a size advantage over Hogna , was tested in laboratory and field experiments.
2. Studies in laboratory arenas, pairing similar-sized individuals of these species and Hogna spiderlings with larger spiders of both species, revealed that intra-guild predation seldom occurs with similar-sized Hogna and Pardosa , however Pardosa will consume small Hogna individuals in laboratory arenas.
3. Field experiments involved stocking high densities (50 m^{– 2} ) of Pardosa and Hogna in enclosures placed in soybean fields. In experiments with spiders of similar size, no interspecific effects were uncovered, but an intraspecific effect was found for Pardosa as its survival and weight gain were lower in the presence of more conspecifics. Large Hogna or Pardosa had no effect on the survival or weight gain of Hogna spiderlings.
4. Although Hogna is a better competitor as an adult, it has no advantage over Pardosa when their size-classes overlap, and Pardosa effects on Hogna may be inconsequential under field conditions. Therefore, the co-existence of these species is fostered by the fact that there are few negative interspecific interactions during their ontogeny.     

草地贪夜蛾幼虫自残捕食量分析

为了明确草地贪夜蛾Spodoptera frugiperda幼虫对同类低龄幼虫的捕食作用,在实验室条件下研究了草地贪夜蛾3~6龄幼虫对不同密度2龄幼虫和4~6龄幼虫对不同密度3龄幼虫的日捕食量,同时从捕食功能的角度解析了草地贪夜蛾高龄幼虫对低龄幼虫的捕食行为;并对不同龄期幼虫进行称重比较,用不同龄期幼虫间的重量关系来替换不同龄期幼虫间的捕食量,得到不同龄期幼虫间的捕食量方程。结果表明,草地贪夜蛾3~6龄幼虫对2龄幼虫和4~6龄幼虫对3龄幼虫的捕食功能反应均符合Holling Ⅱ型功能反应类型。草地贪夜蛾3~6龄幼虫对2龄幼虫的最大捕食量分别为76.47头、85.70头、117.92头、96.05头;4~6龄幼虫对3龄幼虫的最大捕食量分别为38.83头、59.49头、58.87头。高龄幼虫对低龄幼虫的捕食量随猎物密度的增加而增加。最大理论捕食质量方程y=47.231x^0.4591,捕食者的捕食量随着猎物虫态的增大而逐渐减小。研究结果为理解草地贪夜蛾幼虫的种间自残行为规律奠定了一定的理论基础。     

Jack of all trades, master of all: a positive association between habitat niche breadth and foraging performance in pit-building antlion larvae

Species utilizing a wide range of resources are intuitively expected to be less efficient in exploiting each resource type compared to species which have developed an optimal phenotype for utilizing only one or a few resources. We report here the results of an empirical study whose aim was to test for a negative association between habitat niche breadth and foraging performance. As a model system to address this question, we used two highly abundant species of pit-building antlions varying in their habitat niche breadth: the habitat generalist Myrmeleon hyalinus, which inhabits a variety of soil types but occurs mainly in sandy soils, and the habitat specialist Cueta lineosa, which is restricted to light soils such as loess. Both species were able to discriminate between the two soils, with each showing a distinct and higher preference to the soil type providing higher prey capture success and characterizing its primary habitat-of-origin. As expected, only small differences in the foraging performances of the habitat generalist were evident between the two soils, while the performance of the habitat specialist was markedly reduced in the alternative sandy soil. Remarkably, in both soil types, the habitat generalist constructed pits and responded to prey faster than the habitat specialist, at least under the temperature range of this study. Furthermore, prey capture success of the habitat generalist was higher than that of the habitat specialist irrespective of the soil type or prey ant species encountered, implying a positive association between habitat niche-breadth and foraging performance. Alternatively, C. lineosa specialization to light soils does not necessarily confer upon its superiority in utilizing such habitats. We thus suggest that habitat specialization in C. lineosa is either an evolutionary dead-end, or, more likely, that this species' superiority in light soils can only be evident when considering additional niche axes.     

Leaf surface waxbloom in Pisum sativum influences predation and intra-guild interactions involving two predator species

Suppression of shared prey populations by insect predators can be influenced by interactions among these predators (intra-guild interactions). Intra-guild interactions among predators attacking herbivores may be influenced by plant characteristics, but this possibility has not been examined. Plant surface waxes are a ubiquitous and variable morphological feature that are known to affect insect predator behavior, and potentially in- fluence inter-predator interactions. To test this possibility we measured the effectiveness of individual and multiple predators on Pisum sativum L. lines with either wild-type crystalline waxes (normal waxbloom) or with reduced waxbloom resulting from a genetic mutation. On caged five-node plants of each line, reduction in populations of Acyrthosiphon pisum (Harris) (Homoptera: Aphidae) by individuals or pairs of second-instar Hippodamia con- vergens Guerin de Meneville (Coleoptera: Coccinellidae), and second-instar Chrysoperla plorabunda (Fitch) (Neuroptera: Chrysopidae), was significantly greater on the reduced waxbloom plants. Intra-specific interference by H. convergens depended on plant waxbloom type. Pairs of H. convergens larvae were no more effective than individuals of this species at reducing aphid populations on normal waxbloom plants, indicating interference, but were additive in their reduction of aphids on reduced waxbloom plants, indicating no interference. In contrast, pairs of C. plorabunda apparently interfered regardless of plant waxbloom type; pairs were no more effective at reducing aphids than individuals of this species. Heterospecific pairs of H. convergens and C. plorabunda were more effective on reduced waxbloom plants and showed no evidence of interference on either waxbloom type. Differences in behavior of the two predator species provided a partial explanation for the asymmetrical effect on intraspecific interactions in the two species. H. conver- gens spent significantly more time walking and less time ”scrambling” (ineffective locomotion) on reduced waxbloom plants than on normal waxbloom plants, and distributed these activities differently among plant parts on the two waxbloom types. In contrast, C. plorabunda spent the same amount of time walking and scrambling on each waxbloom type, although they distributed this walking and scrambling differently among plant parts of the two waxbloom types. The stronger influence of plant waxbloom on H. convergens behavior is consistent with the difference in intra-specific interference for this species on the two waxbloom types. The mechanisms of intra-specific interference by H. convergens on normal waxbloom plants and by C. plorabunda on both waxbloom types were not determined. Received: 14 July 1999 / Accepted: 10 January 2000     

The effects of food and space on the occurrence of cannibalism and predation among larvae of Anopheles gambiae s.l.

Competitive interactions among the aquatic stages of the malaria mosquito Anopheles gambiae s.l. (Diptera: Culicidae) may affect the resulting adult densities and, hence, the risk of malaria. We investigated the impact of the presence of a fourth‐instar larva (An. gambiae Giles s.s. or An. arabiensis Patton), the quantity of food, and the available space on the survival and development of freshly hatched larvae of An. gambiae s.s. and An. arabiensis. To analyse the results, two proportional hazard models were constructed. The first estimated the effects of all covariates on mortality rate and the second estimated the effects of the covariates on development rate into the third larval instar (L3). A time‐dependent covariate for density, which changed during the experiment as a result of death or development to L3, was included in both models. In the presence of a fourth‐instar larva (L4), survival of the experimental larvae was significantly reduced, but no difference was detected between the presence of L4 An. gambiae and L4 An. arabiensis. The observation that the majority of dead larvae were not recovered in trays with an L4 present suggested that cannibalism and predation occurred readily. Limitation in space significantly increased mortality of larvae, whereas a limitation of food reduced larval development rate, but did not cause mortality per se. From this, we concluded that both cannibalism and predation were enhanced as a result of more frequent interactions within smaller environments, but did not occur for reasons of food shortage. This study shows that inter‐ and intraspecific interactions among larvae of the An. gambiae complex strongly affect survival and development, and that the quantity of food and the available space are important determinants of the outcome of these interactions. Implications of the results are discussed with respect to the population dynamics of both malaria vectors in the field.     

Intraguild predation, cannibalism, and microhabitat use in Calopteryx virgo and Somatochlora metallica larvae: a laboratory experiment

Intraguild predation (IGP) and cannibalism among co-occurring lotic odonate species was studied in Central Finland. A laboratory experiment was performed to assess the microhabitat use and cannibalism between intermediate and late instars of Calopteryx virgo larvae and predation by larger Somatochlora metallica larvae on the intermediate C. virgo instars. The experiment was run in small running-water aquaria where the larvae were able to divide their mutual habitat vertically by clinging onto artificial perches or crawling on the bottom. Life span of the small C. virgo larvae and attack rate on them were compared between the cannibalism and IGP treatments. The effect of predation on the activity, habitat use and spatial distribution of the small C. virgo larvae was examined. The IGP rate was 36%. The prey larvae spent the most of their time on the perches, whereas the S. metallica preferred the substrate. The large C.␣virgo larvae did not cannibalise smaller conspecifics. The presence of a predator (S. metallica) had no effect on the habitat use or activity of the prey (C. virgo) larvae. Habitat use differed more between those species than between conspecifics of different size classes of C. virgo. The spatial distribution between S.␣metallica and C. virgo showed a completely random pattern, whereas the two size classes of C. virgo aggregated in the vegetation. Absence of cannibalism and behavioural observations indicate that C. virgo may have a low tendency for intraspecific aggressions.     

Entomopathogenic nematodes, root weevil larvae, and dynamic interactions among soil texture, plant growth, herbivory, and predation

Greenhouse experiments were conducted to assess the influence of soil texture on the persistence, efficacy and plant protection ability of entomopathogenic nematodes (EPNs) applied to control larvae of the Diaprepes root weevil (DRW), Diaprepes abbreviatus, infesting potted citrus seedlings. Seedlings were grown in pots containing either coarse sand, fine sand, or sandy loam. Three DRW larvae were added to each of 80 pots of each soil type. 24 h later, 20 pots of each soil type that had received weevil larvae were inoculated with EPN infective juveniles (IJs) of one of the following species: Steinernema diaprepesi, Steinernema riobrave and Heterorhabditis indica. Pots of each soil without EPNs were established as controls with DRW and controls without DRWs. Subsequently, pots with larvae received three additional larvae monthly, and the experiment continued for 9 months. Plant root and top weights at the end of the experiment were affected by both soil (P≤0.0001) and nematodes (P≤0.0001), and nematode species protected plants differently in different soils (interaction P≤0.0001). Soil porosity was inversely related to plant damage by DRW, whether or not EPNs were present; and porosity was directly related to the level of plant protection by EPNs. Mortality of caged sentinel weevil larvae placed in pots near the end of the experiment was highest in pots treated with S. diaprepesi. In a second, similar experiment that included an additional undescribed steinernematid of the Steinernema glaseri-group, soil type affected root damage by DRW and root protection by EPNs in the same manner as in the first experiment. Final numbers of S. diaprepesi and Steinernema sp. as measured by real-time PCR were much greater than those of S. riobrave or H. indica in all soils. Across all treatments, the number of weevil larvae in soil at the end the experiment was inversely related to soil porosity. In all soils, fewer weevil larvae survived in soil treated with S. diaprepesi or Steinernema sp. than in controls with DRW or treatments with S. riobrave or H. indica. The results of these experiments support the hypothesis that EPNs provide greater protection of seedlings against DRW larvae in coarse textured soil than in finer textured soil. However, less vigorous growth of the control without DRW seedlings in the two finer textured soils suggests that unidentified factors that stressed seedlings in those soils also impaired the ability of seedlings to tolerate weevil herbivory.     

Threat of predation alters aggressive interactions among spotted salamander (Ambystoma maculatum) larvae

Intraspecific aggression represents a major source of mortality for many animals and is often experienced alongside the threat of predation. The presence of predators can strongly influence ecological systems both directly by consuming prey and indirectly by altering prey behavior or habitat use. As such, the threat of attack by higher level predators may strongly influence agonistic interactions among conspecifics via nonconsumptive (e.g., behaviorally mediated) predator effects. We sought to investigate these interactions experimentally using larval salamanders (Ambystoma maculatum) as prey and dragonfly nymphs (Anax junius) as predators. Specifically, we quantified salamander behavioral responses to perceived predation risk (PPR) from dragonfly nymphs and determined the degree to which PPR influenced intraspecific aggression (i.e., intraspecific biting and cannibalism) among prey. This included examining the effects of predator exposure on the magnitude of intraspecific biting (i.e., extent of tail damage) and the resulting change in performance (i.e., burst swim speed). Salamander larvae responded to PPR by reducing activity and feeding, but did not increase refuge use. Predator exposure did not significantly influence overall survival; however, the pattern of survival differed among treatments. Larvae exposed to PPR experienced less tail damage from conspecifics, and maximum burst swim speed declined as tail damage became more extensive. Thus, escape ability was more strongly compromised by intraspecific aggression occurring in the absence of predation risk. We conclude that multitrophic indirect effects may importantly modulate intraspecific aggression and should be considered when evaluating the effects of intraspecific competition.     

Nutritional benefits of intraguild predation and cannibalism among generalist and specialist phytoseiid mites

1. Intraguild predation and cannibalism are common among predaceous phytoseiid mites (Acari, Phytoseiidae) but the nutritional benefits gained by these processes are poorly understood. 2. The study reported here addressed the questions of whether cannibalism and intraguild predation provide different nutritional benefits and whether the ability to utilise cannibalism and intraguild predation is linked to the diet specialisation of phytoseiid mites. Specialists tested were Phytoseiulus macropilis, Galendromus occidentalis, and Neoseiulus longispinosus; generalists tested were Amblyseius andersoni, Neoseiulus cucumeris, and Neoseiulus fallacis. 3. All generalists and the specialist P. macropilis were able to complete juvenile development with both con‐ and hetero‐specific prey. Juvenile development of generalists was shorter with heterospecific prey than with conspecific prey, whereas development of the specialist P. macropilis did not differ between prey types. Only a few N. longispinosus and G. occidentalis, both specialists, reached adulthood by cannibalism but none reached adulthood by intraguild predation. 4. All generalists were able to sustain oviposition by intraguild predation. Neoseiulus cucumeris and A. andersoni laid more eggs with heterospecific prey than with conspecific prey, whereas N. fallacis had similar oviposition rates with both prey types. No specialist sustained oviposition by intraguild predation or cannibalism. 5. Overall, generalists gained equal or more nutritional benefits by intraguild predation than by cannibalism and were able to utilise phytoseiid intraguild prey as an alternative food source. Specialists gained equal or more nutritional benefits from cannibalism than from intraguild predation. For specialists, con‐ and hetero‐specific phytoseiids may be considered only a supplemental food.     

Habitat disturbance modifies dominance,coexistence, and competitive interactions in tropical ant communities

1. Interspecific competition is a major structuring principle in ecological communities. Despite their prevalence, the outcome of competitive interactions is hard to predict, highly context-dependent, and multiple factors can modulate such interactions. 2. We tested predictions concerning how competitive interactions are modified by anthropogenic habitat disturbance in ground-foraging ant assemblages inhabiting fragmented Inter-Andean tropical dry forests in southwestern Colombia, and investigated ant assemblages recruiting to baits in 10 forest fragments exposed to varying level of human disturbance. 3. Specifically, we evaluated how different components of competitive interactions (patterns of species co-occurrence, resource partitioning, numerical dominance, and interspecific trade-offs between discovery and dominance competition) varied with level of habitat disturbance in a human-dominated ecosystem. 4. Multiple lines of evidence suggest that the role of competitive interactions in structuring ground-foraging ant communities at baits varied with respect to habitat disturbance. As disturbance increased, community structure was more likely to exhibit random co-occurrence patterns, higher levels of monopolization of food resources by dominant ants, and disproportionate dominance of a single species, the little fire ant (Wasmannia auropunctata). At a regional scale, we found evidence for a trade-off between dominance and discovery abilities of the 15 most common species at baits. 5. Together, these results suggest that human disturbance modifies the outcome of competitive interactions in ground-foraging ant assemblages and may promote dominant species that reduce diversity and coexistence in tropical ecosystems.     

Laboratory study of cannibalism and interspecific predation in ladybirds

Abstract.

• 1 In the absence of aphids, adult females of Adalia bipunctata (L.) showed a greater reluctance to eat eggs than males.
• 2 Eggs and young larvae were more vulnerable to cannibalism than older larvae and starved larvae were more vulnerable than well-fed larvae.
• 3 Both egg and larval cannibalism is inversely related to the abundance of aphids.
• 4 Eggs are a better food, in terms of larval growth and survival, than aphids.
• 5 In the absence of aphids interspecific predation occurred, but not equally, between the coccinellids A.bipunctata, A.decempunctata (L.), Coccinella septempunctata L. and C.undecempunctata L.
• 6 Larvae and adults of A. bipunctata and C.septempunctata were reluctant to eat conspecific eggs painted with a water extract of the other species' eggs and larvae of C. septempunctata were more likely to die after eating a few eggs of A.bipunctata than vice versa.
• 7 These results indicate that cannibalism occurs mainly when aphid prey is scarce and is adaptive in that it improves the chances of survival, and coccinellids, to varying degrees, are defended against interspecific predation.

     

Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea

Intraspecific killing has been reported among polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus). Although cannibalism is one motivation for such killings, the ecological factors mediating such events are poorly understood. Between 24 January and 10 April 2004, we confirmed three instances of intraspecific predation and cannibalism in the Beaufort Sea. One of these, the first of this type ever reported for polar bears, was a parturient female killed at her maternal den. The predating bear was hunting in a known maternal denning area and apparently discovered the den by scent. A second predation event involved an adult female and cub recently emerged from their den, and the third involved a yearling male. During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears. We hypothesize that nutritional stresses related to the longer ice-free seasons that have occurred in the Beaufort Sea in recent years may have led to the cannibalism incidents we observed in 2004.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Cannibalism and predation among larvae of the Anopheles gambiae complex

Among the aquatic developmental stages of the Anopheles gambiae complex (Diptera: Culicidae), both inter- and intra-specific interactions influence the resulting densities of adult mosquito populations. For three members of the complex, An. arabiensis Patton, An. quadriannulatus (Theobald) and An. gambiae Giles sensu stricto, we investigated some aspects of this competition under laboratory conditions. First-instar larvae were consumed by fourth-instar larvae of the same species (cannibalism) and by fourth-instar larvae of other sibling species (predation). Even when larvae were not consumed, the presence of one fourth-instar larva caused a significant reduction in development rate of first-instar larvae. Possible implications of these effects for population dynamics of these malaria vector mosquitoes are discussed.     

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation was assessed in the laboratory. In the first experiment, a first instar of one of the two above species was kept with a fourth instar of the other species in a Petri dish. The number of times each first instar larva was encountered by the fourth instar larva and the fate of the first instar was determined over a period of 10 min. The fourth instar larvae captured and killed all the first instar larvae of their own species at the first encounter. However, when presented with fourth instar larvae of the other species the first instar larvae of A. bipunctata and H. axyridis were encountered 6.4 ± 1.3 ( n  = 10) and 19.4 ± 2.1 ( n  = 10), respectively. In this experiment no first instar larvae of H. axyridis , whereas all those of A. bipunctata , were killed.     

Endogenous timing in competitive interactions among relatives

Most evolutionary game theory models solve for equilibrium levels of some behaviour on the restrictive assumptions that players choose their actions simultaneously, and that a player cannot change its action after observing that of its opponent. An alternative framework is provided by sequential or 'Stackelberg' games in which one player commits to a 'first move' and the other has an opportunity to observe this move before choosing its response. Recent interest in the economic literature has focused on Stackelberg games which exhibit 'endogenous timing', i.e. games in which a leader and a follower arise spontaneously as a consequence of each player attempting to maximize its reward. Here, we provide the first demonstration of endogenous timing in an evolutionary context using a simple model of resource competition (the 'tug-of-war' model). We show that whenever two related individuals compete for a share of communal resources, both do best to adopt distinct roles in a sequential game rather than engage in simultaneous competition. Somewhat counterintuitively, the stable solution is for the weaker individual to act as leader and commit to a first move, because this arrangement leads to a lower total effort invested in competition. Endogenous timing offers a new explanation for the spontaneous emergence of leaders and followers in social groups, and highlights the benefits of commitment in social interaction.     

Response of coccinellid larvae to conspecific and heterospecific larval tracks: a mechanism that reduces cannibalism and intraguild predation

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.     

三种捕食性瓢虫成虫对卵的种内自残及其集团内捕食作用

捕食性瓢虫是农田生态系中一类重要的天敌昆虫,种内自残和集团内捕食现象在捕食性瓢虫中普遍存在。本研究在室内通过选择性和非选择性试验比较分析了异色瓢虫、七星瓢虫及龟纹瓢虫成虫对卵的种内自残和集团内捕食作用以及卵表面的化学物质对集团内捕食作用的影响。结果表明:在非选择性试验中,3种捕食性瓢虫成虫对卵表现出相似的取食现象,即对龟纹瓢虫卵取食最多,其次为七星瓢虫卵,对异色瓢虫卵取食相对较少;在选择性试验中,七星瓢虫和龟纹瓢虫较偏好取食同种卵,对异色瓢虫卵取食均较少;而异色瓢虫喜欢取食异种卵,对同种卵取食相对较少。3种瓢虫卵经正己烷漂洗后,异色瓢虫、七星瓢虫和龟纹瓢虫成虫却未对卵表现出取食偏好性。本研究可为捕食性瓢虫组合释放与协调利用、田间集团内捕食作用评定及其在生物防治中的应用提供理论依据。     

The biophysics of pit construction by antlion larvae (Myrmeleon, Neuroptera)

An antlion pit is lined with fine particles during construction. This feature appears to increase the effectiveness of the pit in prey capture. Pit structure is influenced by physical properties of sand and the building behaviour of the antlion. Two physical properties of sand govern pit structure: the angle of repose and Stoke's Law drag force. These two properties complement each other as follows: (a) Since larger particles have a lower angle of repose than smaller particles, fine sand grains tend to stay on the pit walls, whereas larger particles fall to the pit's centre. (b) Large particles have a lower drag to momentum ratio than do small particles. Thus, larger particles are more likely to be thrown out of the pit than are smaller particles. Several behavioural modifications were demonstrated that increase the number of fine particles on the pit walls while reducing construction costs for the antlion. (a) A trajectory angle of 45° is used when the antlion throws particles out of the pit. This angle will maximize the distance to which larger particles are thrown. A trajectory angle of 60° is used at the end of pit construction when the antlion is throwing fine particles on the sides of the pit. This angle reduces the number of these fine particles leaving the pit. (b) Antlions can alter the velocity with which they throw particles. When discarding prey carcasses and debris that have accumulated during prey capture, they use a velocity that is approximately 39% higher than the velocity used during pit construction. (c) By vibrating their forelegs, antlions appear to sift out the finer particles before each throw. This increases the percentage of larger particles discarded from the pit.