Movement of adult pecan weevils Curculio caryae within pecan orchards

1 The pecan weevil Curculio caryae (Horn) (Coleoptera: Curculionidae) is an indigenous pest of pecan Carya illinoinensis (Wangenh.) K. Koch, in North America. Understanding the movement of this pest from the orchard floor to host trees could lead to pest management practices that exploit weevil behaviour and thus reduce insecticide application to the entire orchard canopy. Furthermore, no information exists on diel periodicity of pecan weevil movement. 2 Movement of adult pecan weevils crawling and flying to the host trunk, flying to the host canopy, crawling within the host canopy and flying between host trees was studied using four types of passive traps over four seasons. Each type of trap was used to capture weevils at different locations on or near the tree and to discriminate flying versus crawling behaviour. 3 More pecan weevils crawl to the trunk than fly and a proportion of the population flies directly from the orchard floor into the pecan canopy. The majority of this movement occurs at dusk. 4 The vertical distribution of weevils was generally uniform throughout the canopy but more weevils were captured in suspended traps nearest tree tops, rather than traps near the ground, when flying between trees and this was significantly so for two of 4 years. 5 The results of the present study are contrary to previous reports suggesting that most adult pecan weevils fly to the pecan trunk after emergence from the soil; however, our results did indicate that a proportion of the population flies directly from the orchard floor into the pecan canopy and thus would circumvent strategies that attempt to control weevils moving up the trunk.     

Movement of immature aquatic insects in a lotic habitat

The movement of immature insects up down and across Salem Creek, Ontario, was measured with traps and nets at two week intervals from January to December 1977. Drift of most taxa was more strongly correlated with water velocity from August to December than it was over the whole year. That of Baetis, however, was not correlated with water velocity and it was significantly greater at the side of the stream than at the centre from May to July. Upstream movement, as measured in three different ways, was small compared with drift, being only 2.1, 7.3 and 15.2 percent respectively.Upstream and across stream movements were not consistently different from one another, changes in their intensity apparently merely representing changes in numbers and behaviour of the animals. It is concluded therefore that upstream movement is only random movement.Colonization of empty sediment in trays on and above the substratum confirmed that most reoccupation of denuded areas is by drift. This supports the finding that drift is far geater than random wandering of the insects.     

Factors affecting captures of male citrus leafminer, Phyllocnistis citrella Stainton, in pheromone-baited traps

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is an important world‐wide pest of citrus. Larval mining within leaf flush impacts yield and predisposes trees to infection by citrus canker, Xanthomonas axonopodis pv. citri. The present series of studies sought to identify factors affecting male P. citrella catch in pheromone‐baited traps with the intent of developing effective monitoring. A commercially available pheromone lure (Citralure, ISCA Technologies, Riverside, CA, USA) was highly effective in attracting male P. citrella to traps. Pherocon VI Delta (Trécé Inc., Adair, OK, USA) traps baited with a Citralure captured more male P. citrella than identically baited Pherocon IC Wing traps (Trécé Inc.). The superiority of the Delta‐style trap was found to be due to a 3 cm long closing latch that likely prevents males from flying directly through the trap without capture. Within canopies of mature citrus trees (approximately 3.5 m high), traps at mid‐canopy height (2.0 m) captured more males than traps placed higher (3.5 m) or lower (0.6 m). On the canopy perimeter and in between canopies, traps near ground level (0.6 m height) captured more males than traps at 2.0 and 3.5 m heights. Male catch was greater within the tree canopy or on the canopy perimeter than 2.0 away from the canopy. Traps deployed in trees on the edge of groves captured more males than traps placed 120 and 240 m away from the grove edge and within the grove interior. In non‐pheromone‐treated grove plots, the optimal dosage for catching males was between 0.1 and 1.0 mg of the 3 : 1 blend of (Z,Z,E)‐7,11,13‐hexadecatrienal and (Z,Z)‐7,11‐hexadecadienal; however, in pheromone‐treated plots a higher 10.0 mg dosage lure was most effective. Male catch in pheromone‐baited traps exhibited a diel rhythm with most males captured during scotophase (22:00–23:00 h) and no males captured during photophase.     

Emergence and lateral dispersal of adult Plecoptera and Trichoptera from Broadstone Stream, U.K.

1. Emergence and inland dispersal of adult stoneflies (Plecoptera) and caddisflies (Trichoptera) from Broadstone Stream, an acidic and iron-rich stream in southern England, were studied over 10 months in 1996–1997. Fifteen pyramidal emergence traps were placed randomly in a 200-m stretch. Three Malaise traps were placed above the stream and six more on each side (one wooded, one open) along a transect at distances of 1, 15, 30, 45, 60 and 75 m from the channel. 2. More than 16 000 stoneflies, belonging to 11 species, and just under 400 caddisflies (22 species) were caught. Four dominant stoneflies (Leuctra fusca, Leuctra nigra, Leuctra hippopus and Nemurella pictetii) accounted for 96% and 95% of the catches in the emergence and Malaise traps, respectively. Two caddisflies (Plectrocnemia conspersa and Potamophylax cingulatus) accounted for 63% of the catch in the Malaise traps. Few caddisflies were taken in emergence traps. 3. The emergence periods of L. fusca, L. nigra and L. hippopus were well-defined and unimodal, whereas that of N. pictetii was prolonged and erratic. Overall, more females (1285) emerged than males (740). 4. Female stoneflies and caddisflies were in the majority in the Malaise traps above the stream. On land, significantly more females than males of L. fusca, L. nigra and P. cingulatus were caught. The sex ratio of the remaining species did not deviate significantly from 1:1. 5. The three Malaise traps placed above the stream caught most of the stoneflies though there was also dispersal away from the channel, the numbers caught declining with distance. Exponential models explained between 67% and 99% of the variation in numbers of individuals with distance from the channel in the four common stoneflies. Half the individuals went less than 11–16 m from the stream, while 90% travelled less than 51 m. Significantly more L. nigra and N. pictetii were caught in the woodland than on the open side, whereas L. hippopus showed no overall preference for either side.     

Pollination by the locally endangered island flying fox (Pteropus hypomelanus) enhances fruit production of the economically important durian (Durio zibethinus)

Fruit bats provide valuable pollination services to humans through a unique coevolutionary relationship with chiropterophilous plants. However, chiropterophily in the Old World and the pollination roles of large bats, such as flying foxes (Pteropus spp., Acerodon spp., Desmalopex spp.), are still poorly understood and require further elucidation. Efforts to protect these bats have been hampered by a lack of basic quantitative information on their role as ecosystem service providers. Here, we investigate the role of the locally endangered island flying fox Pteropus hypomelanus in the pollination ecology of durian (Durio zibethinus), an economically important crop in Southeast Asia. On Tioman Island, Peninsular Malaysia, we deployed 19 stations of paired infrared camera and video traps across varying heights at four individual flowering trees in a durian orchard. We detected at least nine species of animal visitors, but only bats had mutualistic interactions with durian flowers. There was a clear vertical stratification in the feeding niches of flying foxes and nectar bats, with flying foxes feeding at greater heights in the trees. Flying foxes had a positive effect on mature fruit set and therefore serve as important pollinators for durian trees. As such, semi‐wild durian trees—particularly tall ones—may be dependent on flying foxes for enhancing reproductive success. Our study is the first to quantify the role of flying foxes in durian pollination, demonstrating that these giant fruit bats may have far more important ecological, evolutionary, and economic roles than previously thought. This has important implications and can aid efforts to promote flying fox conservation, especially in Southeast Asian countries.     

A novel trap for quantifying the dispersal of seeds by wind

Question: Understanding the aerial movement of seed is of great significance to the management of native and invasive plant species, but has proven difficult to measure. Here we examine how a more quantitative approach to measuring the aerial movement of seed can be achieved. Location: SE Australia. Methods: We describe a novel seed trap (the ‘Melbourne trap’), for which the proportion of free‐stream airflow through the trap can be measured, allowing a more quantitative approach to measuring aerial seed movement. We assessed airflow through the Melbourne trap in a wind tunnel and describe how this information, along with measurements of wind speed and direction, can now be used to derive seed density per volume of airflow. We compare the seed capture and retention efficiency of the Melbourne trap with two simpler and cheaper trap designs, bucket traps and sticky traps. Results: Melbourne and bucket traps captured significantly more species than sticky traps. Seed catch was dominated numerically by Lachnagrostis filiformis (G. Forst.) Trin. Melbourne traps proved more effective than sticky traps, but not bucket traps, in capturing L. filiformis, based on intake area. For all other seeds, Melbourne traps were more effective than both bucket and sticky traps. Conclusion: The Melbourne trap design is a significant advance in quantifying seed dispersal by wind. Melbourne traps will improve the capacity and accuracy of studies that seek to: (i) quantify seed fluxes across landscapes boundaries; (ii) assess directionality of dispersal; (iii) understand processes controlling seed release; and (iv) compare dispersal in wind and water.     

The effects of artificial lighting on adult aquatic and terrestrial insects

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Dispersal,feeding and parasitism of adult stoneflies (Plecoptera) at a New Zealand forest stream

The temporal occurrence and dispersal of stoneflies were investigated at a forest stream in the South Island, New Zealand. Although 12 species were taken in Malaise traps, only Spaniocerca zelandica and Cristaperla fimbria (Notonemouridae) were abundant. Adults of S. zelandica were present throughout the year and a wide range of different-sized nymphs, including very small individuals, was also found in all months. In contrast, the emergence period of C. fimbria was limited to about four months in summer and as nymphs are mainly hyporheic, few were taken in Surber samples. Malaise trapping on a 16 m long transect away from the stream and with more distantly located traps in forest and grassland resulted in a very high proportion of males and females of both species being caught within 1 m of the stream edge. Captured females of both species included immature, gravid, and spent individuals. Males and females of both species had almost identical diets dominated by sooty mould fungi, fungal spores, pollen and fine particulate organic matter. High proportions of them were also infected by the encysted larvae of a gordian worm (Nematomorpha) and may be important vectors in its life cycle.     

Mechanism for the small-scale movement of carbon among estuarine habitats: organic matter transfer not crab movement

In theory, carbon is highly mobile in aquatic systems. Recent evidence from carbon stable isotopes of crabs (Parasesarma erythrodactyla and Australoplax tridentata), however, shows that in subtropical Australian waters, measurable carbon movement between adjacent mangrove and saltmarsh habitats is limited to no more than a few metres. We tested whether the pattern in crab δ¹³C values across mangrove and saltmarsh habitats was explained by crab movement, or the movement of particulate organic matter. We estimated crab movement in a mark–recapture program using an array of pitfall traps on 13 transects (a total of 65 traps) covering an area of 600 m² across the interface of these two habitats. Over a 19-day period, the majority of crabs (91% for P. erythrodactyla, 93% for A. tridentata) moved <2 m from the place of initial capture. Crab movement cannot, therefore, explain the patterns in δ¹³C values of crabs. δ¹³C values of detritus collected at 2-m intervals across the same habitat interface fitted a sigmoidal curve of a similar form to that fitting the δ¹³C values of crabs. δ¹³C values of detritus were 2–4‰ more depleted in saltmarsh (−18.5±0.6‰), and 4–7‰ more depleted in mangroves (−25.9±0.1‰) than δ¹³C values of crabs recorded previously in each habitat. Assimilation by crabs of very small detrital fragments or microphytobenthos, more enriched in ¹³C, may explain the disparity in δ¹³C values. Nevertheless, the pattern in δ¹³C values of detritus suggests that crabs obtain their carbon from up to several metres away, but without themselves foraging more then a metre or so from their burrow. Such detailed measurements of carbon movement in estuaries provide a spatially explicit understanding of the functioning of food webs in saltmarsh and mangrove habitats.     

Forest succession and prey availability influence the strength and scale of terrestrial‐aquatic linkages in a headwater salamander system

1. Trophic linkages between terrestrial and aquatic ecosystems are common and sensitive to disruption. However, there is little information on what causes variation in the strength and spatial scale of these linkages. 2. In the highly aquatic adults of the headwater salamander Gyrinophilus porphyriticus (family Plethodontidae), use of terrestrial prey decreases along a gradient from early‐ to late‐successional riparian forests. To understand the cause of this relationship, we tested the predictions that (i) terrestrial prey abundance is lower in late‐successional forests, and (ii) G. porphyriticus adults cannot move as far from the stream to forage in late‐successional forests, thus limiting access to terrestrial prey. 3. We established 100‐m long study reaches on six headwater streams in the Hubbard Brook Experimental Forest, New Hampshire. Three reaches were in early‐successional forests and three were in late‐successional forests. We conducted pitfall trapping for invertebrate prey in June and July of 2005, with three traps at 0, 2, 5 and 10 m from the stream at each reach. In June, July and August of 2004 and 2005, nighttime salamander surveys were conducted at each reach along ten, 10‐m long by 2.5‐m wide transects perpendicular to the stream. 4. Abundance of terrestrial prey was consistently lower in late‐successional forests, suggesting that consumption of terrestrial prey by G. porphyriticus is affected by prey abundance. Contrary to our prediction, G. porphyriticus adults moved farther from the stream in late‐successional forests, suggesting that habitat conditions in late‐successional forests do not limit movement away from the stream, and that lower abundances of terrestrial prey in these forests may cause salamanders to move farther from streams. 5. Our results provide novel insight on the extent of terrestrial habitat use by G. porphyriticus. More broadly, these results indicate that major habitat gradients, such as forest succession, can affect the strength and scale of terrestrial‐aquatic linkages. Application of this insight to the design of vegetation buffers along headwater streams would have widespread benefits to freshwater ecosystems.     

Dispersal of adult caddisflies (Trichoptera) into forests alongside three New Zealand streams

The abundance and taxonomic richness of adult caddisfly faunas were determined at varing distances (up to 200 m) away from three North Island, New Zealand, streams to help define appropriate forested riparian zone widths for adult aquatic insects. Adults were collected using sticky traps and ultraviolet light traps on four occasions over summer. Light traps were more effective at catching caddisflies than sticky traps, but both methods gave similar patterns of declining abundance and taxonomic richness with distance from the stream edge. Abundances of total caddisflies at 20 m were <21% of those caught at the stream edge for both trapping techniques. The same trends were evident for abundances of most common species in light traps, whereas bimodal peaks were evident with distance from the channel edge for percentage females of three common species. More than 30% of species caught at the stream edge was found in light traps at least 70 m into forest at all sites. A faster rate of decline for abundance than richness with distance away from the stream reflected the relatively large distances travelled by representatives of many species. Similar results from the three sites for numbers and species richness indicate that the main area of activity for adult Trichoptera in forested riparian zones was within 30 m of the stream edge at these sites.     

Contradictory results from different methods for measuring direction of insect flight

1. Stream ecologists have been puzzled by the apparent paradox that invertebrate populations persist in headwater streams despite the high frequency with which individuals drift downstream. To resolve this ‘drift paradox’, directions and distances of both larval and adult movement must be identified. Using over 50 interception traps in combination with results from several mark–capture experiments using ¹⁵N as a label, we tested the assumption that interception traps accurately represent the ultimate direction of adult insect flight. 2. In several streams in the Hubbard Brook Experimental Forest, 76% of ¹⁵N‐labelled stoneflies (Leuctra ferruginea) had flown upstream from where they emerged to where they were captured. In contrast, over 60% of stoneflies were flying downstream when captured, i.e. on the upstream side of an interception trap. 3. The instantaneous direction, as indicated by the side of the interception trap on which they were captured, indicated the ultimate flight direction for fewer than 1/3 of the individuals captured. Thus, such traps did not accurately reflect the ultimate flight patterns of individuals, as indicated by mark–capture data. 4. Conclusions drawn from interception trap counts regarding the direction of movement and the distribution and persistence of populations may need to be re‐evaluated. We suggest that better tracking methods, including mass mark–capture studies using stable isotopes, be used to evaluate the potentially complex patterns of adult insect movement and the consequences of that movement for individuals and populations.     

Effect of light colours and weather conditions on captures of Sogatella furcifera (Horváth) and Nilaparvata lugens (Stål)

To study the phototactic responses of white‐backed planthopper, Sogatella furcifera (Horváth) and brown planthopper, Nilaparvata lugens (Stål) to different wavelengths, four colours of light traps (blue, green, yellow and red light‐emitting diodes) were placed in the same rice field along with a traditional black light trap. This study revealed that S. furcifera and N. lugens are more attracted to blue and green lights than that to yellow and red lights. During the 24 nights, compared with the black light trap, the blue LED trap could catch more rice planthoppers at 17 nights. Furthermore, catches of other species (moths and beetles) were substantially reduced in blue LED light traps. Multiple regression models were developed to assess the effect of weather factors on light trap catches of rice planthoppers. Rainfall and mean air temperature at a night mainly affected light trap catches of S. furcifera. Higher rainfall and lower temperature increased light trap catches of S. furcifera. However, wind speed was the main factor affecting the catches of N. lugens, and the lower incidence of catches was found in the night when wind speed exceeded 3.08 m/s. S. furcifera may be flying against wind at light wind nights by 0.3–1.5 m/s, whereas N. lugens may be flying down at strong wind nights by 1.5–3.08 m/s. Relative humidity did not significantly influence on trap catches. Consequently, light wavelengths, precipitation, average temperature and wind should be considered when monitoring rice planthoppers by light traps. Therefore, the blue LED light traps are worth using for monitoring planthoppers.     

Influence of wind conditions and intertrap spacing on pheromone trap catches of male european pine sawfly,Neodiprion sertifer

The spatial distribution of catches of male European pine sawfly,Neodiprion sertifer (Geoffr.) (Hymenoptera, Diprionidae), was studied using different pheromone trap arrays. In hexagonal trap groups, trap interference was evident by reduced catch in the central of seven traps spaced 10 to 40 m apart. When the trap spacings were either 5 or 80 m no significant reduction could be shown. The interaction was more pronounced for strong (100 μg) pheromone ([2S, 3S, 7S]-3,7-dimethyl-2-pentadecanyl acetate) lures than for weak ones (10 μg). Similarly, the inner traps caught less than the outer traps in grids of 6×6 traps spaced 20 or 50 m apart. Mark-release-recapture experiments in the grid array confirmed that a majority of the males originated from outside the trap group and were caught in the first trap they encountered. There were no differences between catches in downwind, crosswind and upwind traps. Thus, no ‘overshooting’ was evident during average conditions, i.e. the sawflies did not divert from the trap initially attracting them by flying to the upwind trap. However, the proportion caught in the upwind traps increased with increasing wind velocity, suggesting more overlapping pheromone plumes at higher wind speeds. Also, the recapture rate of released males increased with increasing wind velocity up to a daily average of 3.1 m/s at 2m, indicating that sawflies more easily find the pheromone source, probably due to a more stable pheromone puff trajectory during higher wind velocities. The application of pheromone traps in e.g. monitoring studies is discussed and a distance of at least 50 m between the traps with strong lures used in the present study is recommended to avoid trap interaction.     

Mortality of the terrestrial adult and aquatic nymphal life stages of Baetis vernus and Baetis rhodani in the Breitenbach, Germany (Insecta: Ephemeroptera)

1. The mortality of Baetis vernus Curtis and Baetis rhodani Pictet during the terrestrial-aerial and aquatic life stages was studied at the Breitenbach near Schlitz, Hesse, Germany. The number of females emerging from the stream was recorded with emergence traps. To estimate mortality of females of both species during terrestrial life, numbers of emerging females were compared with numbers of females returning to the stream for oviposition, as shown by numbers of egg masses found in the stream. 2. Mortality of female B. vernus during their terrestrial life stage was 98.8%. It was 91.2 and 96.6%, respectively, during the first and second generations of B. rhodani. 3. To estimate the mortality of both sexes of B. rhodani during the aquatic life stage, the number of eggs laid by the first generation was compared with the number of adults emerging during the second generation. 4. Mortality during the aquatic phase (both sexes combined) of B. rhodani was 91.1%. 5. Mortality during the terrestrial life stages was at least as high, if not higher than during the aquatic stages. Evidently, there is a considerable export of organic material into the terrestrial environment around the stream. Mortality during terrestrial life may be an important regulator of population size.     

Influence of carbon dioxide on numbers of Culicoides midges collected with suction light traps in South Africa

To implement risk management against diseases transmitted by species of Culicoides Latreille, 1809 (Diptera: Ceratopogonidae), it is essential to identify all potential vectors. Light traps are the most commonly used tool for the collection of Culicoides midges. Given the indiscriminate artificial attraction of light, traps will collect all night‐flying insects rather than only livestock‐associated Culicoides midges. Factors that may increase the efficacy of traps, especially for livestock‐associated Culicoides midges, require investigation. In the present study, results obtained with Centers for Disease Control (CDC) and Onderstepoort light traps baited with carbon dioxide (CO₂) were compared with those of unbaited controls. Comparisons were made using two replicates of a 4 × 4 randomized Latin square design. With both trap types, the mean numbers of Culicoides midges collected in 16 baited traps were higher than those caught in 16 unbaited traps. Although exceptionally low numbers were collected with the CDC traps, the increases in the numbers and frequency of collection of Culicoides imicola Kieffer, 1913 were more pronounced in the CDC traps compared with the Onderstepoort traps. These results indicate that the addition of CO₂ may increase the efficiency of these traps for the collection of C. imicola and other livestock‐associated Culicoides species.     

Geographical distribution pattern and interisland movements of Orii’s flying fox in Okinawa Islands, the Ryukyu Archipelago, Japan

The study of mobile animals such as flying foxes in insular habitats involves clarifying the population status on each island and determining the factors affecting movement patterns among the islands in their distributional range. We visited 25 of the Okinawa Islands and documented the number of Orii’s flying foxes Pteropus dasymallus inopinatus from August 2005 to May 2006. We also conducted a monthly road census on the main island (Okinawa-jima Island) and six adjacent islands from June 2006 to January 2007 and counted the number of fruit-bearing trees of the bats’ four main food plants. The results of classification and regression tree analysis suggested that distance from the main island was a primary factor in determining the distribution pattern and population size of this flying fox, whereas island area, number of plant species, and food availability did not directly affect population size. The number of flying foxes on each island tended to decrease with an increase in distance from the main island; no flying foxes existed on islands >30 km away from the main island. On the other hand, the results of the monthly census showed that the population size on each island fluctuated seasonally. Individuals may move between islands in response to seasonal changes in food availability. In conclusion, the distribution and abundance of Orii’s flying foxes in the Okinawa Islands may be determined by the rate of immigration/emigration, depending on each island’s distance from the main island. Seasonal changes in food availability may act as a trigger for interisland movement, but that movement may be restricted by island connectivity.     

Large scale Agriotes spp. click beetle (Coleoptera: Elateridae) invasion of crop land from field margin reservoirs

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Stand-level distribution and movement of Platypus quercivorus adults and patterns of incidence of new infestation

Abstract 1 Flying populations of an ambrosia beetle, Platypus quercivorus (Murayama), a vector of an ambrosia fungus Raffaelea quercivora, which causes deciduous oak diebacks in Japan, were determined by sticky screen traps. 2 Platypus quercivorus beetles tended to move upwards along slopes. The highest concentrations of flying beetles usually occured at the upper forest margins. 3 During the period when the number of flying beetles was increasing, the incidence of newly infested trees spread from the epicentre into the forest. During the period when the number of flying beetles was decreasing, the epicentre shrank into the upper forest edge. Newly infested trees did not occur in this period because most trees had already been infested. 4 Near the upper forest edge, where many beetles were highly concentrated throughout the season, the number of new entry holes decreased greatly after the initial attack early in the season, although many adults were present throughout the period.     

The effect of plant spacing on the number of aphids trapped over cocksfoot and kale crops

The response to plant spacing by flying and landing aphids has been studied using cylindrical and horizontal sticky traps over cocksfoot and kale crops. Some aphid species showed a significant response to spacing, being caught more frequently over wide-than close-spaced crops; the regressions of catches over widely-spaced on those over close-spaced plants suggested that most of the species caught followed this trend irrespective of the host plant. The landing response to spacing on horizontal traps at 0.3 m was normally greater than that on cylindrical traps at 1 m. At 1 m, some species (e.g. Aphis fabae gp.) gave a different response to spacing in the two crops, whilst others (e.g. Rhopalosiphum oxyacanthaé) responded similarly to both crop spacings. In contrast to previous results with other aphid species and spaced groundnuts, the landing response of Rhopalosiphum spp. was elicited both when there was a cover crop (clover) between widely-spaced drills of cocksfoot and by widely-spaced cocksfoot alone. It is suggested that one stimulus eliciting the landing response with widely-spaced plants is the electromagnetic emission from bare earth between the plants. Aphid landing behaviour was influenced by the spacing of both cocksfoot and kale plants.