The biocontrol potential of Philodromus (Araneae,Philodromidae) spiders for the suppression of pome fruit orchard pests

A number of different generalist (polyphagous) predators occur in agroecosystems. Yet their biocontrol potential has been little investigated in detail. Philodromus species (Philodromidae) belong to the dominant spider species occurring in commercial orchards. We studied in detail the trophic functional traits of Philodromus albidus, Philodromus aureolus, and Philodromus cespitum (Philodromidae) by means of (1) the analysis of natural prey; and (2) experiments on acceptance of a variety of prey taxa. We found that the three philodromids are euryphagous. We classified prey species into three categories according to their function in the orchard: beneficial species, indifferent species, and pests. Philodromid spiders captured mostly other spiders in the field because spiders were most available. As concerns pests, the philodromids preyed mostly on Brachycera and Sternorrhyncha. They selected Acari and Brachycera. Indifferent species, such as Collembola and Nematocera, were also highly selected. In the laboratory, philodromids accepted mostly pests, such as lepidopterans, brachycerans, and aphids, while other spiders were accepted the least. The three philodromids have differentiated trophic niches with respect to prey size not only in the adult stage but throughout their ontogenetic development: P. albidus utilized smaller prey than the other two species. We conclude that the philodromids have a potential as biocontrol agents because they prey mostly on pests but their predation pressure is reduced due to higher selectivity for the indifferent fauna.     

Consumption,developmental and reproductive attributes of two con-generic ladybird predators under variable prey supply

Availability of aphid prey in habitat is often heterogeneous in space and time and its deprivation causes severe effects on life attributes of ladybird predators. Sometimes ladybirds locate high prey biomass while on certain occasions prey biomass may be either medium/low or altogether absent. Present study has been designed in view of three prey biomass conditions in nature, viz. low, medium and high, selecting Coccinella septempunctata and Coccinella transversalis as experimental ladybirds. Results revealed that consumption, developmental and reproductive attributes of both ladybirds changed in response to prey availability. On high prey biomass larvae had higher consumption and growth rates, developed faster and had low mortality, while emerging adults were large in size, had high consumption rates and utilized prey biomass maximally on production of eggs, self maintenance and survival. In contrast low prey biomass reduced chances of larval survival and emerging adults were small in size, had poor prey consumption rates, low fecundity, egg fertility and short life span. Females exhibited triangular fecundity and egg fertility functions and plateau shaped prey consumption rate function with age, indicating towards their highest reproductive performance during middle age on three prey biomasses; being highest on high prey biomass. On three prey biomasses, females had higher body biomass conversion efficiency during pre- and post-oviposition periods and higher egg biomass conversion efficiency during oviposition period; being highest on high prey biomass. Thus middle aged ladybirds reared on high prey biomass may suppress pest populations better than those reared on low/medium prey biomass.     

Is different degree of individual specialization in three spider species caused by distinct selection pressures?

Individual specialization (IS), i.e. the relatively narrower niche of individuals compared to their population, can be caused by the interplay between intrinsic and extrinsic factors. We studied IS on prey type and size in three congeneric euryphagous sympatrically occurring species: Philodromus albidus, Philodromus aureolus, and Philodromus cespitum. We performed prey acceptance experiments in standardized laboratory conditions using adult females. We also studied possible factors affecting IS. As intrinsic factors, we measured aggressiveness toward prey and spider size as the measures of behavioral and morphological differences, respectively. As extrinsic factors, we studied the composition of the guild of actively hunting spiders in the area from where the philodromids were collected. We computed the degree of inter- and intraspecific crowding as a measure of inter- and intraspecific competition, respectively. Then we computed competition coefficients from census data in order to estimate the strength of interspecific competition among three species. There was no IS on prey type in any studied species. In terms of prey size, only P. albidus was found to be individually specialized, while there was no IS in the other two species. There was a significant effect of aggressiveness, but no significant effect of body size on IS in P. albidus. This species was the least aggressive of the studied species. The philodromids were the dominant actively hunting spiders in the study area. P. albidus was exposed to a relatively higher degree of interspecific than intraspecific competition, whereas in the other philodromids the situation was reversed. The presence of interspecific competition between P. albidus and the other two species was confirmed by the census data analysis. We documented context-dependent IS in Philodromus species. We argue that the higher degree of IS in P. albidus was influenced by interference competition mainly from the other two philodromid species. The niches of the other two species were influenced by food limitation, which decreased their IS.     

Aggregation of polyphagous predators in response to multiple prey: ladybirds (Coleoptera: Coccinellidae) foraging in alfalfa

The spatial distribution of polyphagous predators may often reflect the integration of aggregative responses to local densities of multiple species of prey, and as such may have consequences for the indirect linkages among the prey sharing these predators. In a factorial field experiment in which we manipulated local prey densities within a field of alfalfa in Utah (USA), we tested whether aphidophagous ladybirds would aggregate not only in response to their primary aphid prey, but also in response to an abundant alternative prey, the alfalfa weevil (Hypera postica [Gyllenhal]). Native North American ladybirds (primarily Hippodamia convergens Guerin and H. quinquesignata quinquesignata [Kirby]) responded only to spatial variation in aphid density. In contrast, the introduced ladybird, Coccinella septempunctata L., aggregated also at local concentrations of the weevil late in the experiment when weevil density was high and aphid density was relatively low throughout all experimental plots. The results support the hypothesis that C. septempunctata is more responsive than are native ladybirds to the availability of alternative prey in alfalfa, which may account in part for the displacement of native ladybirds from alfalfa by the introduced species as aphid numbers have declined. The differing responses of the native and introduced ladybirds to spatial patterns of the alternative prey underscore the importance of extending the study of predator aggregation to understand better how polyphagous predators distribute themselves in response to spatial patterns of multiple species of potential prey.     

Contrasting population growth parameters of the aphidophagous Scymnus nubilus and the coccidophagous Nephus reunioni

Compared to coccidophagous ladybirds, aphidophagous ladybirds develop and live faster. They also produce more eggs at a faster rate. As we wanted to know how these traits influence population dynamics, we have determined the population growth parameters for the aphidophagous Scymnus nubilus Mulsant (Coleoptera: Coccinellidae) and the coccidophagous Nephus reunioni Fürsch (Coleoptera: Coccinellidae) fed Rhopalosiphum padi (L.) (Hemiptera: Aphidoidea) and Planococccus citri (Risso) (Hemiptera: Coccoidea) respectively under controlled laboratory conditions. Net reproductive rate, intrinsic rate of natural increase, and finite rate of increase were all significantly higher, and generation time and doubling time were both significantly shorter in S. nubilus compared to N. reunioni. The reproductive output of the aphidophagous species rapidly reaches a peak and then sharply declines while it is regularly distributed throughout adult life in the coccidophagous predator. A significant difference in late survival was found, with S. nubilus exhibiting higher survival. Adaptation to the consumption of aphids and coccids occurred in several species during the co-evolutionary history of ladybird beetles and their prey. Thus, comparing other species would be valuable to confirm the differences reported here.     

Survival, development and life tables of two congeneric ladybirds in aphidophagous guilds

Two congeneric aphidophagous ladybirds, Coccinella septempunctata and Coccinella transversalis, were reared on three aphid species, Lipaphis erysimi, Myzus persicae and Aphis nerii, to estimate the effect of prey quality and intra- and interspecific interactions on their survival and development of life stages. Mortality of first instar ladybirds of both species was highest feeding on A. nerii. Preimaginal mortafity was lowest when feeding on L. erysimi （C. septempunctata, 1.6% and C. transversalis, 3.2%）, and highest when feeding on A. nerii （ C. septempunctata, 6.2% and C. transversalis, 8.2%）. Comparatively higher weight and larger size of C. septempunctata along with the lower levels of mortality recorded suggested that it is more likely to have acted as an intraguild predator than C. transversalis. High recorded mortality of C. transversalis is attributed to probable intraguild predation on account of its smaller size. The major sources of mortality were probably cannibalism, intraguild predation and other unknown factors. Lower prey quality increased the incidence of cannibalism and intraguild predation, especially in C. transversalis. The investigation suggests an intrinsic competitive advantage for C. septempunctata over C. transversalis in guilds of three aphid species.     

Prey preference and life tables of the predatory mite Parasitus bituberosus (Acari: Parasitidae) when offered various prey combinations

Parasitus bituberosus Karg (Acari: Parasitidae) is one of the predatory mite species inhabiting mushroom houses. It is known to accept a wide range of prey, suggesting that it may be a promising candidate for the biological control of key pests of mushroom culture. In our study it did not show any prey preference among four groups of small organisms often occurring in mushroom growth medium, namely rhabditid nematodes, pygmephorid mites, and sciarid and phorid fly larvae. Nevertheless, the type of food these predators fed on affects their development. The shortest egg-to-adult development time was obtained on a nematode diet. On a diet of phorid larvae, mite development stopped at the deutonymph stage; none reached adulthood. All other diets sufficed to reach the adult phase. Female fecundity when fed nematodes and sciarid larvae did not differ, but it was much lower when fed pygmephorid mites. Other life table parameters confirmed that pygmephorid mites constituted the worst diet for P. bituberosus. The highest intrinsic rate of population increase (r _m  = 0.34) was obtained on the nematode diet; when fed sciarid larvae and pygmephorid mites it was 0.25 and 0.14, respectively. Our study provides good reasons to further test P. bituberosus as biocontrol agent of especially sciarid flies and nematodes, especially when the compost is well colonized by mushroom mycelium (which retards nematode growth).     

Ultimate Predators: Lionfish Have Evolved to Circumvent Prey Risk Assessment Abilities

Invasive species cause catastrophic alterations to communities worldwide by changing the trophic balance within ecosystems. Ever since their introduction in the mid 1980''s common red lionfish, Pterois volitans, are having dramatic impacts on the Caribbean ecosystem by displacing native species and disrupting food webs. Introduced lionfish capture prey at extraordinary rates, altering the composition of benthic communities. Here we demonstrate that the extraordinary success of the introduced lionfish lies in its capacity to circumvent prey risk assessment abilities as it is virtually undetectable by prey species in its native range. While experienced prey damselfish, Chromis viridis, respond with typical antipredator behaviours when exposed to a common predatory rock cod (Cephalopholis microprion) they fail to visibly react to either the scent or visual presentation of the red lionfish, and responded only to the scent (not the visual cue) of a lionfish of a different genus, Dendrochirus zebra. Experienced prey also had much higher survival when exposed to the two non-invasive predators compared to P. volitans. The cryptic nature of the red lionfish has enabled it to be destructive as a predator and a highly successful invasive species.     

Decline in native ladybirds in response to the arrival of Harmonia axyridis: early evidence from England

1. Harmonia axyridis (Coleoptera: Coccinellidae) is an invasive non‐native ladybird in Europe, where it was introduced as a biological control agent of aphids and coccids. 2. This study assesses changes to ladybird species assemblages, in arboreal habitats, over a 3‐year period encompassing the invasion phase of H. axyridis in eastern England. The effects of H. axyridis and other factors (weather and prey availability) on native ladybirds are assessed. 3. Harmonia axyridis increased from 0.1% to 40% of total ladybirds sampled, whilst native aphidophagous species declined from 84% to 41% of total ladybirds. The actual number of native aphidophagous ladybirds per survey decreased from a mean of 19.7 in year 1, to 10.2 in year 3. 4. Three ladybird species in particular experienced declines: Adalia bipunctata, Coccinella septempunctata, and Propylea quattuordecimpunctata. Harmonia axyridis was the most abundant species by the end of the study. 5. The decline in native aphidophagous ladybirds could be attributed to competition for prey and intraguild predation of eggs, larvae, and pupae by H. axyridis. Physiological and behavioural traits of H. axyridis are likely to confer an advantage over native ladybird species.     

Forager abundance and its relationship with colony activity level in three species of South American Pogonomyrmex harvester ants

The proportion of foragers in ant colonies is a fairly constant species-specific characteristic that could be determined by intrinsic or extrinsic factors. If intrinsic factors are relevant, species with similar life history characteristics (e.g., colony size and foraging strategies) would be expected to have a similar proportion of foragers in their colonies. Within the genus Pogonomyrmex, North American species can vary largely in their colony size, whereas only species with small colonies are known in South America. We studied the characteristics of the foraging subcaste in three sympatric South American species of Pogonomyrmex harvester ants, and compared it with the available information on other species of the same genus. We used two mark-recapture methods and colony excavations to estimate the number and proportion of foragers in the colonies of P. mendozanus, P. inermis, and P. rastratus, and to test the relationship between forager external activity levels and abundance per colony. Forager abundance in the three studied species was lower than in most North American species. The percentage of foragers in their colonies ranged 7–15 %, more similar to North American species with large colonies than to those with small colony size. Foraging activity was positively correlated with forager abundance in all three species, implying that colony allocation to number of foragers allows for higher food acquisition. Further comparative studies involving a wider range of traits in South and North American species would allow to unveil the role of environmental factors in shaping each species’ particular traits.     

Dispersal potential of native and exotic predatory ladybirds as measured by a computer-monitored flight mill

The performance of three species of predatory ladybirds was compared in a flight mill and the effect of diet on their flight parameters was tested. The invasive ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) outperformed Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) and Adalia bipunctata (L.) (Coleoptera: Coccinellidae) in terms of flight distance, duration and velocity. Harmonia axyridis flew at least two times further, needed three times less breaks and flew two times faster than C. montrouzieri and A. bipunctata fed the same diet. Ladybirds reared on eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) performed better than their counterparts reared on natural prey (aphids for H. axyridis and A. bipunctata, mealybugs for C. montrouzieri). The findings of this study indicate that comparative flight studies can be useful to identify candidate biocontrol agents with pronounced dispersal abilities and thus can yield significant evidence to be used in an environmental risk assessment. However, it also demonstrates that variability related to mass rearing conditions should not be ignored when standardizing a risk assessment procedure for candidate biocontrol agents.     

Functional response of two aphidophagous ladybirds searching in tandem

The functional response of two ladybird species, Propylea dissecta (Mulsant) and Coccinella transversalis Fabricius in combination was studied in an effort to determine the impact of two predators on the increasing density of aphid, Aphis gossypii Glover infesting leaves of bottle gourd, Lagenaria vulgaris Seringe. The ladybirds were exposed to prey density in three combinations using adult females: (i) one P. dissecta and one C. transversalis together, (ii) two P. dissecta, and (iii) two C. transversalis, for 24 h. Prey consumption increased curvilinearly with prey density in all three combinations. It was maximum when heterospecifics searched together. The prey were handled and consumed significantly faster (9.51 min) by heterospecifics in combination, followed by two C. transversalis (11.32 min) and two P. dissecta (12.52 min). The attack rate was maximum (0.00274) by heterospecifics followed by the two C. transversalis (0.00166) and two P. dissecta (0.00092). The synergistic effect on the prey consumption may possibly be due to spatial distribution of P. dissecta and C. transversalis in terms of feeding sites, with the former being negatively, and the latter being positively geotactic. Field release of two predator species in tandem is recommended for biocontrol of A. gossypii because of the potential for synergistic action by these natural enemies.     

Acquired phototrophy in Mesodinium and Dinophysis – A review of cellular organization,prey selectivity,nutrient uptake and bioenergetics

Acquired phototrophy, i.e. the use of chloroplasts from ingested prey, can be found among some species of dinoflagellates and ciliates. The best studied examples of this phenomenon in these groups are within the ciliate genus Mesodinium and the dinoflagellate genus Dinophysis, both ecologically important genera with a worldwide distribution. Mesodinium species differ considerably in their carbon metabolism. Some species rely almost exclusively on food uptake, while other species rely mostly on photosynthesis. In Mesodinium with acquired phototrophy, a number of prey organelles in addition to chloroplasts may be retained, and the host ciliate has considerable control over the acquired chloroplasts; Mesodinium rubrum is capable of dividing its acquired chloroplasts and can also photoacclimate. In Dinophysis spp., the contents of ciliate prey are sucked out, but only the chloroplasts are retained from the ingested prey. Some chloroplast house-keeping genes have been found in the nucleus of Dinophysis and some preliminary evidence suggests that Dinophysis may be capable for photoacclimation. Both genera have been claimed to take up inorganic nutrients, including NO₃⁻, indicating that processes beyond photosynthesis have been acquired. M. rubrum seems to depend upon prey species within the Teleaulax/Plagioselmis/Geminigera clade of marine cryptophytes. Up until now, Dinophysis species have only been maintained cultured on M. rubrum as food, but other ciliates may also be ingested. Dinophysis spp. and M. rubrum are obligate mixotrophs, depending upon both prey and light for sustained growth. However, while M. rubrum only needs to ingest 1–2% of its carbon demand per day to attain maximum growth, Dinophysis spp. need to obtain about half of their carbon demand from ingestion for maximum growth. Both Mesodinium and Dinophysis spp. can survive for months in the light without food. The potential role for modeling in exploring the complex balance of phototrophy and phago-heterotrophy, and its ecological implications for the mixotroph and their prey, is discussed.     

Evolution of prey holding behaviour and large male body size in Ninox owls (Strigidae)

The hawk owl genus Ninox is unique among raptorial birds in that it includes three species in which males are substantially larger than females. This is a reversal of the normal pattern observed in both diurnal and nocturnal raptorial birds in which females are larger. Interestingly, these three Ninox species also are both the largest of the 22 species in the genus and the only species that exhibit the striking behaviour of ‘prey holding’ in which large (> 600 g) mammalian or avian prey is captured at night and held with body parts intact, and draped below a roost for the entire day without being consumed. Because explanations of the evolution of large male size suggest that it results from competition among males, the adaptive significance of prey holding was studied in a wild population of powerful owl Ninox strenua. Prey holding is largely confined to breeding males and its occurrence varies significantly across the breeding cycle, being most frequent during incubation and brooding. The study did not clearly resolve whether prey holding is a form of food storage or territorial display; however, both functions can select for large male body size and therefore play a significant role in the evolution of nonreversed size dimorphism. Although female‐only incubation and brooding is typical of Ninox owls and other owl species, prey holding appears to occur only in the large Ninox species because of the unique combination of large body size, large prey size, separate sex roles, and obligate cavity nesting. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 284–292.     

Influence of snail mucus trails and first snail meal on the behavior of malacophagous sciomyzid larvae

There has been considerable focus on the natural enemies of snails, particularly those of medical and veterinary significance. Much attention has focussed on members of the Family Sciomyzidae (Diptera), the majority of which feed on a range of mollusc species. However, little is known about the influence of first snail meal on subsequent prey choices, an important consideration in biocontrol. We examined neonate larval responses of Ilione albiseta to fresh and aged snail mucus trails of three snail species. Median neonate response rates to aged mucus trails for all three snail species tested were significantly (P < 0.001) weaker than for fresh mucus trails indicating a strategy which enhances the likelihood of reaching prey snail species without expending energy following “cold” trails. More than 78% of first instar larvae, fed on one snail species (Radix peregra or Stagnicola palustris) and subsequently offered a choice of these two snail species for the second snail meal, selected the snail species of the first snail meal suggesting that the first snail meal influences subsequent prey selection. However, the impact of the first snail meal on larval trail-following behavior is less clear-cut. While there may be some preference for the mucus trail of the snail species on which neonate larvae have fed, this does not exclude the larvae from following the mucus trails of other snail species. The results are discussed in the context of the potential use of I. albiseta as a biocontrol agent of vectors of snail borne diseases.     

Cannibalism and interspecific predation in two predatory ladybirds in relation to prey abundance in the field

Life tables for two predatory ladybirds,Coccinella septempunctata andHarmonia axyridis, were constructed in two years in which prey abundance differed. The prey aphid,Aphis gossypii, was abundant on its primary host from late May to late June. Females ofH. axyridis andC. septempumctata laid their eggs during the increase and peak in aphid abundance. The oviposition period ofC. septempunctata started before and was shorter than that ofH. axyridis. In both species, intraguild predation and/or cannibalism of the egg and fourth instar stages, but rarely of other developmental stages, were observed. Fourth instar larvae ofH. axyridis had to complete their development when aphids were scarce more frequently than those ofC. septempunctata. The highest frequency of intra- and interspecific predation was of fourth instarH. axyridis larvae. In terms of intraguild predation, the larvae ofH. axyridis preyed on larvae ofC. septempunctata, but the reverse was not observed. Percentage survival from egg to adult inH. axyridis was higher than inC. septempunctata in both years, and least in both species in the year of low aphid abundance. These results suggest that prey abundance influenced the frequency of cannibalism and intraguild predation, which were important in structuring this guild of ladybirds.     

Effectiveness of ladybirds as biological control agents: Patterns and processes

Aphidophagous species of ladybirds have generally proved ineffective biocontrol agents, whereas many coccidophagous species have proved very effective, especiallyRodolia cardinalis (Caltagirone & Doutt, 1989). Two hypotheses have been proposed to account for this pattern: the optimum food utilization/satiation hypothesis (Mills, 1982) and the generation time ratio hypothesis (Kindlmann & Dixon, 1996). In this paper the extensive literature on ladybirds is used to test these hypotheses.     

Prey preference and prey switching in Anthocoris minki Dohrn (Hemiptera: Anthocoridae)

The understanding of host specificity of predacious insects is one of the most important problems in the investigation of biological control. Prey preference and the potential for prey switching in Anthocoris minki Dohrn (Hem.: Anthocoridae) was assessed in two- choice experiments under environmentally controlled conditions. Manly's preference index was used to compare A. minki predation on Agonoscena pistaciae Burckhardt and Lauterer (Hem.: Psyllidae) versus Psyllopsis repens Loginova (Hem.: Psyllidae) but showed no statistically significant evidence for preference. Anthocoris minki did prefer psyllids (Agonoscena pistaciae and Psyllopsis repens) over aphids (Forda hirsuta Mordvilko (Hem.: Pemphigidae) and Aphis craccivora Koch (Hem.: Aphididae)). The predator also consumed significantly more 2nd instar than 4th instar nymphs of P. repens. Switching behavior experiments showed that A. minki did not preferentially attack the most abundant prey when the prey combination was either biased toward A. pistaciae or toward F. hirsuta. Linear regression between preference indices and prey ratios indicated an overall preference for psyllids over aphids. The results suggest that a psyllid-specialized feeder such as A. minki is more likely to be effective biocontrol agent against psyllid species and less effective at reducing the numbers of other pest species that might co-occur with psyllids.     

Exotic ladybirds for biological control of herbivorous insects – a review

Since the late 19th century, exotic ladybirds (Coleoptera: Coccinellidae) have been used extensively for suppressing herbivorous insects of economic importance. In recent decades, the introduction of non‐native biological control (BC) agents has been greatly limited due to the awareness of the potential non‐target effects of introductions. Nonetheless, recent episodes of biological invasions of economically important pests have raised the need to carefully consider whether the expected benefits of pest control go beyond the possible environmental risks of introduction. To better understand the factors that contributed to successful BC programs, here we review the literature behind classical and augmentative BC using exotic ladybirds. Additionally, by means of case studies, we discuss the BC efficacy of selected exotic species, e.g., Coccinella septempunctata L., Harmonia axyridis (Pallas), and Hippodamia variegata (Goeze), and their position within the communities of predators in the introduced areas of USA, Canada, and Chile. In Europe, much of the research on exotic ladybirds has been conducted on the undesired impact of H. axyridis. Therefore, we summarize the risk assessment data for this species and review the field research investigating the ecological impact on European aphidophagous predators. According to the BIOCAT database of classical BC programs, 212 ladybird species belonging to 68 genera have been released in about 130 years of BC activity, with 14.6% of introductions having resulted in partial, substantial, or complete control of the target pest. However, because post‐release evaluation of establishment and BC success has not always been conducted, this rate could underestimate the successful cases. Among other factors, ladybird establishment and pest suppression mostly depend on (1) intrinsic factors, i.e., high voracity, synchronized predator‐prey life cycle, and high dispersal ability, and (2) extrinsic factors, i.e., adaptability to the new environment and landscape composition. This review contributes to improved understanding of ladybirds as exotic BC agents.     

Aggressive use of Batesian mimicry by an ant-like jumping spider

Batesian and aggressive mimicry are united by deceit: Batesian mimics deceive predators and aggressive mimics deceive prey. This distinction is blurred by Myrmarachne melanotarsa, an ant-like jumping spider (Salticidae). Besides often preying on salticids, ants are well defended against most salticids that might target them as potential prey. Earlier studies have shown that salticids identify ants by their distinctive appearance and avoid them. They also avoid ant-like salticids from the genus Myrmarachne. Myrmarachne melanotarsa is an unusual species from this genus because it typically preys on the eggs and juveniles of ant-averse salticid species. The hypothesis considered here is that, for M. melanotarsa, the distinction between Batesian and aggressive mimicry is blurred. We tested this by placing female Menemerus sp. and their associated hatchling within visual range of M. melanotarsa, its model, and various non-ant-like arthropods. Menemerus is an ant-averse salticid species. When seeing ants or ant mimics, Menemerus females abandoned their broods more frequently than when seeing non-ant-like arthropods or in control tests (no arthropods visible), as predicted by our hypothesis that resembling ants functions as a predatory ploy.