Seasonal pattern in food gathering of the weaver ant Oecophylla longinoda (Hymenoptera: Formicidae) in mango orchards in Benin

Prey capture and food scavenging activities of Oecophylla longinoda were monitored through regular weekly samplings during two consecutive years (2009–2010) in a large mango orchard of the Borgou Department of Benin, West Africa, a main mango production area located in the Sudan agro-ecological zone. In both years, interspecific competition with other ants occurred mainly during the dry season (January to March) resulting in increased captures of Formicinae, Myrmicinae and Ponerinae. More prey was caught during the rainy season (end April to end October) than during the rest of the year, with Diptera and Coleoptera prey peaking in May and June, respectively, along with the mango season. As insect prey quickly decreased during November to December weaver ants increasingly collected seeds and plant debris. A total of 241 species of insects were captured including 61 species (25.3%) associated with mango and a few with cashew, among which 48 mango pest species (78.7% of species associated with mango tree). Only five species (2.1%) of beneficial insects were captured. It is concluded that the presence of O. longinoda colonies is beneficial to perennial tree cropping systems such as mango and cashew.     

Ants provide nutritional and defensive benefits to the carnivorous plant Sarracenia minor

Ants can have important, but sometimes unexpected, effects on the plants they associate with. For carnivorous plants, associating with ants may provide defensive benefits in addition to nutritional ones. We examined the effects of increased ant visitation and exclusion of insect prey from pitchers of the hooded pitcher plant Sarracenia minor, which has been hypothesized to be an ant specialist. Visitation by ants was increased by placing PVC pipes in the ground immediately adjacent to 16 of 32 pitcher plants, which created nesting/refuge sites. Insects were excluded from all pitchers of 16 of the plants by occluding the pitchers with cotton. Treatments were applied in a 2 × 2 factorial design in order to isolate the hypothesized defensive benefits from nutritional ones. We recorded visitation by ants, the mean number of ants captured, foliar nitrogen content, plant growth and size, and levels of herbivory by the pitcher plant mining moth Exyra semicrocea. Changes in ant visitation and prey capture significantly affected nitrogen content, plant height, and the number of pitchers per plant. Increased ant visitation independent of prey capture reduced herbivory and pitcher mortality, and increased the number of pitchers per plant. Results from this study show that the hooded pitcher plant derives a double benefit from attracting potential prey that are also capable of providing defense against herbivory.     

Reducing losses inflicted by insect pests on cashew,using weaver ants as a biological control agent

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Temporal abundance of African weaver ant,Oecophylla longinoda (Hymenoptera: Formicidae) under unimodal rainfall pattern in Tanzania

Weaver ants, Oecophylla spp., provide adequate protection to crops against insect pests when their populations are high and stable. A study was conducted in a cashew field in Tanzania from November 2012 to October 2014 to determine temporal abundance of O. longinoda. We determined (i) the number of shoots with O. longinoda in a tree (established fortnightly) monitored at four cardinal points of a tree, using 1 m² wooden quadrats, (ii) the percentage of branches with ant trails per tree per month and (iii) the number of visible ant nests within the tree canopy per month. Furthermore, we assessed the association of weather and phenology with O. longinoda populations. More weaver ant populations were recorded during reproductive and vegetative phases of cashew. We recorded significant positive associations between rainfall and temperature with the number of shoots with O. longinoda (p < .001), as well as relative humidity with the number of nests (p < .001). The percentage of shoots with O. longinoda was significantly associated with cashew growth phases. Rainfall and temperature negatively affected the number of nests. Consideration of cashew phenology and weather parameters can greatly enhance successful weaver ant augmentation strategies.     

Comparing different methods for trapping mated queens of weaver ants (Oecophylla longinoda; Hymenoptera: Formicidae)

The predatory efficiency of African weaver ants Oecophylla longinoda and their utilisation in protein production is a function of ant abundance. Reliable control of insect pests in tropical crops is achieved when ant populations are constantly high. Transplanted populations of weaver ant colonies containing egg-laying queens are more stable than those without. Achieving such stability through collection of colonies established in the wild is usually difficult because of uncertainty in locating the nest containing the egg-laying queen. In this study, we investigated four methods that may be used to collect mated queens that subsequently can be used to stock ant nurseries. The catch efficiencies of (1) leaf traps, (2) paper traps (both types providing a refuge for founding queens), (3) random search for queens and (4) light trapping were compared. Light trapping was the most efficient way to collect queens followed by leaf traps, random search and, last, paper traps. Light trapping and random search, though, required the presence of a person throughout the ant's mating season (several months), whereas this was not required when using leaf and paper traps.     

Temperature: Diet Interactions Affect Survival through Foraging Behavior in a Bromeliad‐Dwelling Predator

Temperature, food quantity and quality play important roles in insect growth and survival, influencing population dynamics as well as interactions with other community members. However, the interaction between temperature and diet and its ecological consequences have been poorly documented. Toxorhynchites are well‐known biocontrol agents for container‐inhabiting mosquito larvae. We found that Toxorhynchites haemorrhoidalis larvae (Diptera: Culicidae) inhabiting water‐filled rosettes of tank bromeliads catch and eat prey of both aquatic (mosquito larvae) and terrestrial origin (ants), using distinct predatory methods. They carried out frontal attacks on ants, but ambushed mosquito larvae. In choice tests, T. haemorrhoidalis favored terrestrial prey. Temperature had a significant effect on predator development and survival through its interaction with diet, but did not alter the preference for ants. T. haemorrhoidalis larvae emerged quickly when fed only mosquito larvae, whereas all individuals died before pupation when fed only ants. We conclude that behavioral factors (i.e., attraction to ants that disturb the surface of the water) overtake physiological factors (i.e., the adverse outcome of elevated temperature and an ant‐based diet) in determining a predator's response to temperature:diet interactions. Finally, because T. haemorrhoidalis larvae preferentially feed on terrestrial insects in tank bromeliads, mosquito larvae may indirectly benefit from predation release.     

Efficiency of insect capture by Sarracenia purpurea (Sarraceniaceae), the northern pitcher plant

Pitcher plants (Sarracenia purpurea L.) attract insects to pitchers and then capture them in fluid-filled, pitfall traps, but how efficient are pitcher plants at capturing prey in their natural environment? We monitored insect activity by videotaping pitchers and analyzing videotapes for several variables including identity of each visitor and outcome of each visit (e.g., departure or capture). Efficiency of capture (i.e., number of captures per number of visits) was low. Overall efficiency of capture was 0.83–0.93%, depending on whether potential prey were broadly or narrowly defined. Ants constituted 74% of the potential prey. Efficiency of capture of ants was even lower at 0.37%. Potential prey were more likely to visit pitchers with greater red venation and less water in the pitcher. There was no correlation between number of potential prey visiting a pitcher and pitcher age, length, or mouth width. Also, number of potential prey visits did not correlate with plant size, air temperature, time of day or date of videotaping. While the overall efficiency of prey capture was very low, pitcher plants may still benefit from the additional nutrients. However, the relationship between ants and S. purpurea remains an enigma, since it is unclear whether the plants capture enough ants to compensate for nectar lost to ants.     

Oecophylla smaragdina food conversion efficiency: prospects for ant farming

Oecophylla ants are sold at high prices on several commercial markets as a human delicacy, as pet food or as traditional medicine. Currently markets are supplied by ants collected from the wild; however, an increasing interest in ant farming exists as all harvest is easily sold and as ant farming can be combined with the use of the ants in biological control programmes in tropical plantations where pest insects are converted into ant biomass. To assess the cost‐benefits of ant farming based on artificial feeding, food consumption and food conversion efficiency (ECI) of Oecophylla smaragdina (Fabricius) was tested under laboratory conditions. Of the two types of food offered, the ants ingested 76% pure sucrose and 24% insect prey (dry weights) leading to ECI’s of 29% and 39% including brood only or brood plus imago gain, respectively. Based on Thai sugar and protein food costs and ant brood selling prices these efficiencies led to rates of return from 1.52 to 4.56, respectively, if: (i) protein is supplied from commercial products; or (ii) alternatively supplied from free sources such as insects and kitchen waste. These results suggest that Oecophylla ant farming may become highly profitable and deserves further research.     

Recruitment Behavior During Foraging in the Neotropical Ant Gnamptogenys moelleri (Formicidae: Ponerinae): Does the Type of Food Matter?

Gnamptogenys moelleri nests in bromeliads and feeds on an array of food items, including dead and live animals, and nectar. Field data in Brazilian forests indicate that G. moelleri hunts solitarily, while retrieving is performed both by solitary workers for small items, or by a group of recruited workers for large items. This flexible foraging strategy was investigated in the laboratory through a series of experiments to assess the context in which recruitment is elicited. Three types of food were used: 50% honey solution, large insect prey, and cluster of small insects. For all food types the first encounter by a scout resulted in increased numbers of ants leaving the nest and finding the food in the arena. After finding liquid food or large prey, the forager returns to the nest and transmits information to nestmates about food location on the substrate. The successful scout repeatedly taps the sting on the ground, and recruited ants collectively retrieve the large insect to the nest. On the other hand, there is no transmission of information to nestmates about the location of small clumped prey, although the returning scout induces nestmates to leave the nest and hunt. Because foraging in G. moelleri is restricted mostly to the nest bromeliad, and small worker size (0.5 cm) precludes capturing large prey solitarily, recruitment behavior widens the spectrum of food items consumed by this ant species. Although recruitment behavior in ponerines has already been reported to vary with the type and size of a food source, this study also shows that the transmission of information about food location depends on the type of food found (large prey or liquid food versus cluster of small prey).     

Honeydew collection by the invasive garden ant Lasius neglectus versus the native ant L. grandis

Honeydew collection performed by the invasive ant Lasius neglectus and by the native ant L. grandis was compared. The invasive ant collected 2.09 kg of honeydew per tree while the native ant collected 0.82 kg. The aphid Lachnus roboris was visited by both ant species. In holm oaks colonized by L. neglectus, aphid abundance tended to increase and its honeydew production increased twofold. The percentage of untended aphids was lower in holm trees occupied by L. neglectus. As tending ants also prey on insects, we estimated the percentage of carried insects. The native ant workers carried more insects than the invasive ant. Both ant species preyed mainly on Psocoptera and the rarely tended aphid, Hoplocallis picta. We conclude that the higher honeydew collection achieved by L. neglectus was the consequence of (1) its greater abundance, which enabled this ant to tend more Lachnus roboris and (2) its greater level of attention towards promoting an increase of honeydew production. Handling editor: Heikki Hokkanen     

Effect of supplementary feeding of Oecophylla longinoda on their abundance and predatory activities against cashew insect pests

Many studies have shown the efficiency of using weaver ants (Oecophylla species) as natural biocontrol agents against agricultural pests. Supplementary feeding could promote fast growth of this ant's population and discourage them from moving away. However, such artificial feeding might slow down ants search rates and in this way make them less efficient bio-agents. The experiments were conducted for two consecutive seasons at Naliendele Research Station. Cashew trees planted at a spacing of 12 m × 12 m in 2002 were used to investigate whether supplementary feeding could enhance foraging behaviour of Oecophylla longinoda. Fed O. longinoda colonies fed weaver ants (FWA) were supplemented with a 30% sugar solution and approximately 22 g of finely ground fish meat at two-week intervals while the unfed colonies unfed weaver ants (UWA) had access to only naturally occurring food sources. Weaver ant densities and pest damage were monitored fortnightly on newly damaged shoots, panicles and fruits and nut yields assessed after each harvest season. The results revealed that there was a significant difference (P < 0.05) with higher weaver ant densities in the FWA compared to UWA colonies and significantly lower (P < 0.05) pest damage levels were recorded on weaver ant treatments compared to plots without weaver ants. No significant differences (P > 0.05) in yields and mean damage levels were recorded between the two weaver ant treatments. Highest nut yield (4.22 ± 0.30 kg/tree and 5.37 ± 0.27 kg/tree) was recorded in the fed colonies, followed by non-fed colonies (4.20 ± 0.30 kg/tree and 4.88 ± 0.24 kg/tree) and the least (2.66 ± 0.19 kg/tree and 2.99 ± 0.19 kg/tree) was recorded from the untreated controls in 2012/2013 and 2013/2014, respectively. The studies indicated that supplementary feeding could boost weaver ants to higher population levels without reducing their effectiveness as biocontrol agents.     

A comparison of pitfall traps with bait traps for studying leaf litter ant communities.

A comparison of pitfall traps with bait traps for sampling leaf litter ants was studied in oak-dominated mixed forests during 1995-1997. A total of 31,732 ants were collected from pitfall traps and 54,694 ants were collected from bait traps. They belonged to four subfamilies, 17 genera, and 32 species. Bait traps caught 29 species, whereas pitfall traps caught 31 species. Bait traps attracted one species not found in pitfall traps, but missed three of the species collected with pitfall traps. Collections from the two sampling methods showed differences in species richness, relative abundance, diversity, and species accumulation curves. Pitfall traps caught significantly more ant species per plot than did bait traps. The ant species diversity obtained from pitfall traps was higher than that from bait traps. Bait traps took a much longer time to complete an estimate of species richness than did pitfall traps. Little information was added to pitfall trapping results by the bait trapping method. The results suggested that the pitfall trapping method is superior to the bait trapping method for leaf litter ant studies. Species accumulation curves showed that sampling of 2,192+/-532 ants from six plots by pitfall traps provided a good estimation of ant species richness under the conditions of this study.     

The effects of artificial lighting on adult aquatic and terrestrial insects

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Quantification of insect nitrogen utilization by the venus fly trap Dionaea muscipula catching prey with highly variable isotope signatures.

Dionaea is a highly specialized carnivorous plant species with a unique mechanism for insect capture. The leaf is converted into an osmotically driven trap that closes when an insect triggers sensory trichomes. This study investigates the significance of insect capture for growth of Dionaea at different successional stages after a fire, under conditions where the prey is highly variable in its isotope signature. The contribution of insect-derived nitrogen (N) was estimated using the natural abundance of 15N. In contrast to previous 15N studies on carnivorous plants, the problem emerges that delta15N values of prey insects ranged between -4.47 per thousand (grasshoppers) and +7.21 per thousand (ants), a range that exceeds the delta15N values of non carnivorous reference plants (-4.2 per thousand) and soils (+3 per thousand). Thus, the isotope-mixing model used by Shearer and Kohl to estimate the amount of insect-derived N is not applicable. In a novel approach, the relationships of delta15N values of different organs with delta15N of trapping leaves were used to estimate N partitioning within the plant. It is estimated that soon after fire approximately 75% of the nitrogen is obtained from insects, regardless of plant size or developmental stage. The estimates are verified by calculating the average isotope signatures of insects from an isotope mass balance and comparing this with the average measured delta15N values of insects. It appears that for Dionaea to survive and reach the flowering stage, seedlings must first reach the 6th-leaf rosette stage, in which trap surface area nearly doubles and facilitates the capture of large insects. Large amounts of nitrogen thus made available to plants may facilitate an enhanced growth rate and the progressive production of additional large traps. Dionaea reaches a maximum abundance after fire when growth of the competing vegetation is suppressed. About 10 years after fire, when grasses and shrubs recover, Dionaea becomes overtopped by other species. This would not only reduce carbon assimilation but also the probability of catching larger prey. The amount of insect-derived nitrogen decreases to 46%, and Dionaea becomes increasingly dependent on N-supply from the soil. Competition for both light and N may cause the near disappearance of Dionaea in older stages of the fire succession.     

Capture and Mortality Rates of Ducks in Selected Trap Types

ABSTRACT We evaluated different trap styles and related mortality of trapped ducks (Anas spp.) for 3 field seasons as part of the United States-Canada Cooperative Waterfowl Banding Program. During 2002, we evaluated 4 trap designs and caught 10,966 ducks. Trap style affected capture rates (P = 0.018, F₅ = 9.02), with Benning II and oval traps catching more ducks than cloverleaf and star traps. In 2003, we tested 3 trap styles and caught 10,849 ducks. Trap style affected duck capture rates (P < 0.01, F₅ = 15.16), with oval traps with 6-m lead panels catching more ducks than Benning II traps and cloverleaf traps. During 2004, we tested 3 trap styles and caught 11,737 ducks. Trap style affected capture rates (P < 0.01, F₅ = 11.23), with oval traps with 6-m leads catching more ducks than either the oval trap without leads or Benning II traps. Trap style affected mortality rates of ducks, but overall mortality of trapped ducks was low with a rate of 1.16% in 2002, 0.32% in 2003, and 0.17% in 2004; mortality was not a major problem in our study. Waterfowl managers may be able to catch more ducks using oval traps with leads without increasing mortality of captured ducks.     

Invasive interactions: can Argentine ants indirectly increase the reproductive output of a weed?

The direct and indirect interactions of invasive ants with plants, insect herbivores, and Hemiptera are complex. While ant and Hemiptera interactions with native plants have been well studied, the effects of invasive ant–scale insect mutualisms on the reproductive output of invasive weeds have not. The study system consisted of Argentine ants (Linepithema humile), boneseed (Chrysanthemoides monilifera monilifera), and sap-sucking scale insects (Hemiptera: Saissetia oleae and Parasaissetia nigra), all of which are invasive in New Zealand. We examined the direct and indirect effects of Argentine ants on scale insects and other invertebrates (especially herbivores) and on plant reproductive output. Argentine ants spent one-third of their time specifically associated with scale insects in tending behaviours. The invertebrate community was significantly different between uninfested and infested plants, with fewer predators and herbivores on ant-infested plants. Herbivore damage was significantly reduced on plants with Argentine ants, but sooty mould colonisation was greater where ants were present. Herbivore damage increased when ants were excluded from plants. Boneseed plants infested with Argentine ants produced significantly more fruits than plants without ants. The increase in reproductive output in the presence of ants may be due to increased pollination as the result of pollinators being forced to relocate frequently to avoid attack by ants, resulting in an increase in pollen transfer and higher fruit/seed set. The consequences of Argentine ant invasion can be varied; not only does their invasion have consequences for maintaining biodiversity, ant invasion may also affect weed and pest management strategies.     

Foraging,recruitment and predation by Decamorium uelense (Sanstchi) (Formicidae: Myrmicinae) on termites in Southern Guinea Savanna,Nigeria

Summary The myrmicine ant Decamorium uelense is a predator of small termites which feed inside their food sources of roots and plant debris. The ant uses a specialized recruitment regime to secure its prey. A scout ant searches for foraging termites and returns to the nest where it recruits a column of 10–30 ants which attack and immobilize the termites. A mass recruitment phase is then instigated, with larger numbers of ants retrieving the prey. The major prey item is Microtermes (consumed at an annual rate of 632 termites m^-2), with other small termites accounting for 0.5% of the total predation. The annual predation of Microtermes in primary savanna woodland by D. uelense removes 74% of the standing population.     

The role of odour and visual cues in the pan-trap catching of hoverflies (Diptera: Syrphidae)

Coloured pan traps are frequently used to attract and catch insects, such as in the monitoring of populations of beneficial insects in classical or conservation biological control. They are also used in the evaluation of the recovery of insect populations after disturbance and in many other situations where an estimate of relative insect numbers is required. However, the fact that traps may be visible to the insects over a considerable distance can influence the interpretation of catch data. This difficulty may arise, for example, if traps along a transect can attract insects from some or all of the other transect positions. This study compared the effect of different coloured traps on attraction and catch of hoverflies. The hypothesis was that completely yellow traps would attract hoverflies from a distance, while traps that were green outside and yellow inside would catch fewer flies because only those from above or near the trap can see the yellow stimulus. A subsidiary hypothesis was that rose water would enhance hoverfly capture rates. For the two main hoverfly species captured, Melanostoma fasciatum (Macquart) and Melangyna novaezelandiae (Macquart), significantly more individuals were caught in completely yellow traps than in yellow and green or in completely green traps. Moreover, the addition of rose water increased the number of hoverflies caught significantly. It is suggested that if a measure of hoverfly numbers relating to a particular distance along a transect is required, consideration should be given to the ability of hoverflies to see yellow traps from a distance. The use of traps that are green outside would more accurately reflect the local abundance of hoverflies. If higher trap catches of hoverflies are needed for statistical purposes, rose water can enhance catches.     

Food habits of the sympatric insectivorous bats Rhinolophus rouxi and Hipposideros lankadiva from Sri Lanka

The diets of Rhinolophus rouxi and Hipposideros lankadiva were studied during October 1984 in Sri Lanka, by analysing the faeces collected from individuals. As a comparison, insects were collected with a light trap at different sites in the study area.
Rhinolophus rouxi showed no specialization for any particular insect prey. The diet composition in this species shows a good correspondence to the composition in dry weight of insects collected by light traps. Dipterans were under-represented in the faeces compared to the numbers trapped. This suggests that R. rouxi forages unselectively on prey larger than the generally very small dipterans. After the first monsoon showers, the remains of beetles, especially scarabaeids, and termites were more common in the faeces of R. rouxi. Bats caught at hourly intervals during one night showed an increase in the proportion of moths consumed.
In contrast, H. lankadiva was found to feed mainly on beetles, particularly scarabaeids, together with large, slow-flying insects such as bugs or nuptial ants. The proportion of beetles (79%-100%) in the faeces of this species was about three times higher than their representation in the insect collections. This suggests that H. lankudiuu forages selectively.     

Short-term effects of mowing on insect communities in Japanese peach orchards

A population survey of insects was conducted at peach orchards in Okayama Prefecture, western Japan, every 2 weeks during May–October in 2011. Pitfall traps were used to sample more than 4000 insects at 10 orchards: 8 orchards where ground vegetation had been managed by mowing and 2 with management by herbicide application. Numbers of insect species (species richness) and numbers of insects captured in pitfall traps (trap catches) were greater after mowing. Details of the effects of mowing on insect communities were examined at four orchards that had been mowed. Results suggest that species richness and trap catches increase up to 5 days after mowing and then return to their original state. Increased species richness and trap catches were mainly attributable to the increase of ants (Formicidae) and carabids (Carabidae). These results suggest that ants and carabids actively seek prey animals that have been killed, injured, or damaged by mowing.