Pit building antlions
Euroleon nostras
have been submitted to artificial cues in order to delineate their faculty to localize a prey. Series of propagating pulses in sand have been created from an ...extended source made of 10 piezoelectric transducers equally spaced on a line and located at a large distance from the pit. The envelope of each pulse encompasses six oscillations at a carrier frequency of 1250 Hz and up to eight oscillations at 1666 Hz. In one set of experiments, the first wave front is followed by similar wave fronts and the antlions respond to the cue by throwing sand in the opposite direction of the wave front propagation direction. In another set of experiments, the first wave front is randomly spatially structured while the propagation of the wave fronts inside the envelope of the pulse are not. In that case, the antlions respond less to the cue by throwing sand, and when they do, their sand throwing is more randomly distributed in direction. The finding shows that the localization of vibration signal by antlions are based on the equivalent for hearing animals of interaural time difference in which the onset has more significance than the interaural phase difference.
During a study of the family Myrmeleontidae of Iran, specimens of the tribe Myrmeleontini, housed in Hayk Mirzayans Insect Museum were examined. Specimens of Euroleon nostras and Myrmeleon noacki ...were identified for the first time from Iran. An identification key, illustrations and distributional maps are presented for the Iranian species of Myrmeleontini.
Some sit-and-wait predators, such as antlion larvae, construct traps to capture passing prey. The location of these traps depends on many abiotic and biotic factors, including temperature and the ...presence of conspecifics, which probably stimulate behaviours that minimize the costs and maximize the benefits of trap building. Here, we exposed second instar antlion larvae to elevated temperatures of 25°C (mild treatment) or 31°C (harsh treatment) for one month and then transferred them to common conditions (20°C) to examine the effects of previous thermal treatment on aggregation tendency and trap size. We predicted that antlions that experienced harsh conditions would subsequently increase the neighbouring distance and trap diameter to reduce competition with conspecifics and improve prey capture success, compensating for past conditions. In contrast with these predictions, antlions exposed to harsh conditions displayed a trend in the opposite direction, towards the decreased neighbouring distance. Furthermore, some of these antlions also built smaller traps. We discuss possible reasons for our results. The effects of previous thermal exposure have rarely been considered in terms of trap construction in antlions. Described effects may possibly apply to other sit-and-wait predators and are significant considering that many of these predators are long-lived.
Predators use different foraging modes, ranging from active to ambush predation. We investigated the predatory behaviour of two antlion species, the pit-builder Euroleon nostras and the ...non-pit-builder Neuroleon microstenus, both considered as ambush predators but with different predatory strategies. Since the pit-builders evolved from non-pit-builders, we focused on the similarities and differences in behavioural patterns and capture success. We found that most behavioural patterns occur in both species, although the non-pit-builder's behaviour is less stereotypic and exhibits more behavioural patterns than in the pit-builder when comparing behaviour from prey introduction to jaw set without pit-construction. In N. microstenus, two distinct behavioural sequences were noted, which depend on the method of prey carcass clearing. This is the first report describing two methods of prey-carcass clearing in a non-pit-builder: tossing or dropping the prey. We also noted the presence of camouflage in the non-pit-builder, considered as an important mechanism in anti-predator tactics.
Sand-dwelling antlion larvae are well known predators with a highly specialized prey-catching strategy, which either construct efficient pitfall traps or bury themselves in the sand ambushing prey on ...the surface. Although habitat selection in antlions has been extensively studied, little is known about the role substrate density plays in such behavioural decisions. We thus first quantified the natural substrate densities of 13 antlion species by collecting soil samples from 18 different field sites. We found that natural substrate densities varied from 121 g/l to 1562 g/l. The substrate densities of three non-pit-building species (Neuroleon microstenus, Distoleon tetragrammicus, Nophis teillardi) ranged from medium to high, while those of obligatory pit-builders (Euroleon nostras and eight Myrmeleon species) were more variable. The substrate density of the facultative pit-builder Cueta sp. was high. Next, we explored the responses of the pit-building antlion E. nostras to different substrate densities using both a habitat choice and a complementary no-choice experiment. We hypothesized that antlions should be capable of distinguishing between substrate types and that pit size should decrease with increased substrate density. When allowed to choose among eight substrate densities, E. nostras larvae preferred to build their pits in the fractions with low densities (i.e., 121, 353 and 512 g/l) and only a small proportion constructed pits in high density fractions (i.e., 1312 and 1546 g/l). A complementary no-choice experiment demonstrated that pit diameter, pit depth and pit angle were negatively correlated with substrate density. These reductions in pit size can negatively affect prey capture success.
► Substrate densities in natural habitats of 13 antlion species originating from four continents are presented. ► We examined effect of substrate density on pit-building decision and pit size in antlions. ► Pit diameter, pit depth and pit angle are negatively correlated with substrate density, which affect capture success.
A mixed antlion community is recorded at the “Fringilla” Research Station, “Rybachii” Biological Station, Curonian Spit, Baltic Sea, Kaliningrad Province, Russia; the adults were captured using ...ornithological traps and the larvae were found on sand dunes around. The ratio of the larval numbers in the mixed colonies of Myrmeleon tschernovi sp. n., Myrmeleon formicarius L., and Euroleon nostras (Geoffr.) is 100: 3: 2. The new species is described, the other two are recorded in Kaliningrad Province for the first time. Morphologically, Myrmeleon tschernovi sp. n. is similar to Myrmeleon bore (Tjed.), being its neighbor in the Baltic Region and occupying its econiche. The most characteristic distinctions between these species are found in the male genitalia and in the larval head chaetotaxy and color pattern.
► The results presented here provide insight supporting the role of autophagy as a cell survival mechanism for the periods of food deprivation. ► The influence of starvation on the midgut epithelial ...cells of the instar antlion larvae Euroleon nostras was studied using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy filtering TEM (EFTEM). ► The structure of the spherites changed during the period of larval life. ► Additionally, changes were present in the chemical composition of spherites from fed and non-fed E. nostras.
We analysed structural differences between midgut epithelial cells of fed instar antlions’ larvae Euroleon nostras and starved ones. In starved larvae the presence of autophagolysosome-like structures was observed, which are characteristic structures associated with autophagy. The results presented here provide insight supporting the role of autophagy as a cell survival mechanism for the periods of food deprivation. Additional structural changes in the cytoplasm were seen in the spherites. The ultrastructure and chemical composition of spherites in the midgut epithelial cells of first, second and third instar larvae were observed with light microscopy and transmission electron microscopy (TEM). A detailed characterization of the elemental composition of the spherites was studied using analytical electron microscopy; a combination of energy dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy filtering TEM (EFTEM) was applied. The structure and elemental composition of the spherites changed during the period of larval life. Moreover, changes in chemical composition were found between spherites from fed and starved E. nostras. In fed first instar larvae, the spherites contained an organic matrix, composed of C, N and O. In this matrix, P, Cl, Ca and Fe were detected. In starved first instar larvae, only C, N and P were present. The spherites of fed second instar larvae were rich in organic and inorganic elements and were composed of C, N, O, Na, Mg, P, S, Cl, K, Ca, Mn, Fe and Zn. In starved second instar larvae, the chemical elements N, O, P, Ca and Fe were found. In fed third instar larvae, the spherites contained C, N, O, Na, Mg, P, Cl, K, Ca, Mn, Fe, Co and Zn. In starved third larvae, C, O, Si, Ca, and Fe were detected. Generally, the spherites are exploited in starved larvae. These results suggest that the elemental supply of spherites may provide crucial support for physiological processes during starvation periods amongst E. nostras instar larvae. In some cases in fed second and fed third instar larvae, spherites were seen in the lumen of the midgut. Such spherites could serve as reservoirs for nontoxic waste material that cannot be metabolized.
The larvae of the antlion Euroleon nostras are pit-builders, constructing pitfall traps in loose sand. The number of pits and the pit diameter are recorded when larvae are kept in substrates with ...different particle sizes. The most convenient pit-building sand fractions are two fractions with fine sand (<or= 0.23 mm; 0.23-0.54 mm). The largest pits are constructed in sand with a particle size of 0.23-0.54 mm. In this sand fraction, larvae of all three instars most readily build pits. No pits are constructed in sand with a particle size greater than 1.54 mm. First- and second-instar larvae avoid building pits in substrates of particle size 1-1.54 mm, but third-instar larvae construct pits in this sand fraction. It is assumed that the antlion is capable of distinguishing between substrate types and this hypothesis is tested by giving larvae the choice of building a pit in one of four particle-size fractions. Larvae of all three instars prefer to build pits in the fraction with a particle size of 0.23-0.54 mm. Only third-instar larvae build pits in all four fractions, but only occasionally in the coarser fraction.
. Pit‐building antlions are predators with a unique predation strategy, namely using pitfall traps constructed in loose sand to catch prey. Here, prey escape‐time in the field is measured by ...introducing ants into one of four different treatment arenas. The first treatment lacks pits and antlions, the second includes 10 antlions that did not build pits, the third comprises eight artificially constructed pits, and the fourth is a treatment of eight antlions in pits and two without pits. Their pits are of a similar size to those used in the third treatment. When antlions are present without constructing pits, they impede the dispersal of prey. The mean escape‐time for one half of the released ants is twice as long with antlions present as without them. When pits are present, the time taken for one half of the released ants to escape the predator is more than 10 times as long as when pits are absent. Escape‐time from artificial pits is three times that from nonpit building antlions. Pits hinder the escape of ants and therefore increase the amount of time that the prey is available for capture. In the area where the pits are occupied by antlions, escape‐time is four times longer than in a treatment with similar sized artificial pits. Thus, it appears that not only a pit, but also the presence of antlions influences the capture success.
In this paper, we describe the hitherto largely overlooked effect of temperature on the pupil of insect compound eyes. In the turnip moth Agrotis segetum and in two other nocturnal insects with ...superposition eyes, the lacewing Euroleon nostras and the codling moth Cydia pomonella, the pupil not only opens and closes with changes in the ambient light level, as expected, but also with changes in temperature in the absence of light. In complete darkness, the pupil of A. segetum responds over a wide range of temperatures, with the pupillary pigments migrating to a light-adapted position when the animal is exposed to either low or high temperatures. At temperatures between 21.0 and 22.7 C, the pigments migrate to the fully dark-adapted position, resulting in an open pupil and maximal eye glow. Pupil closure at high temperatures shows two distinct thresholds: the first at 23.8+/-0.7 C and a second some degrees higher at 25.7+/-1.2 C (means +/- s.d., N=10). Temperatures exceeding the first threshold (the activation temperature, T(a)) initiate a closure of the pupil that is completed when the temperature exceeds the second threshold (the closure temperature, T(c)), which causes rapid and complete migration of pigment to the light-adapted position. All temperatures above T(a) affect the pupil, but only temperatures exceeding T(c) result in complete closure. Temperatures between T(a) and T(c) cause a slow, partial and rather unpredictable closure. The lacewing and the codling moth both show very similar responses to those of A. segetum, suggesting that this response to temperature is widespread in superposition eyes. The possibility that the ambient temperature could be used to pre-adapt the eye to different light intensities is discussed.
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