Showing papers on "Lasius published in 2003"

Different impacts of two species of aphid-attending ants with different aggressiveness on the number of emerging adults of the aphid's primary parasitoid and hyperparasitoids

Abstract: The impacts of two species of ants (Lasius niger and Pristomyrmex pungens) attending the cotton aphid (Aphis gossypii) on the number of emerging adults of the aphid’s primary parasitoid (Lysiphlebus japonicus) and hyperparasitoids were assessed experimentally at a no-pesticide mandarin grove. L. japonicus females were observed foraging frequently in aphid colonies attended by either ant species, with more females in P. pungens-attended than in L. niger-attended colonies, but rarely in aphid colonies where ants were artificially excluded. Females were less often attacked by P. pungens workers than by L. niger workers, so that they stayed longer and oviposited into more aphids in P. pungens-attended than in L. niger-attended colonies. Attendance by each ant species reduced predator numbers in aphid colonies, compared to colonies where ants were absent, although P. pungens was slightly less effective in repelling predators. Therefore, both ant species incidentally protected parasitized aphids from predators. Consequently, L. japonicus-mummies were abundant in colonies attended by either ant species, with more mummies in P. pungens-attended colonies, and were scarce in ant-excluded colonies. The hyperparasitism and predation on L. japonicus larvae within mummies occurred more frequently in P. pungens-attended than in L. niger-attended colonies, but mummy predation rate was only 20% in the former. As a result, the number of emerging L. japonicus adults did not differ significantly between aphid colonies attended by the two ant species, but significantly more hyperparasitoids emerged in colonies attended by the relatively less aggressive P. pungens than in colonies attended by L. niger.

How does colony growth influence communication in ants

Abstract: As Lasius niger societies grow from incipient nests to mature colonies, their foraging strategies shift from the individual exploitation of food sources to mass recruitment. Colony size instead of age is the key factor that shapes the exploratory and foraging responses of Lasius niger: a drastic reduction (or increase) of the population elicits an activity profile similar to that observed in younger (or older) societies of the same size. As a colony grows, the proportion of patrollers significantly decreases while the proportion of conveyors remains rather constant. As regards the energetic return, it increases with incipient nest size due to the replacement of minims by ordinary workers of larger crop capacity. We also demonstrate that minims of incipient nests modulate their trail-laying behaviour according to the social context, in this case the colony size. During their ontogenesis, L. niger colonies exhibit a progressive integration of individual foragers into a network of communication, the adaptive significance of which is discussed.

Positive and negative effects of leaf shelters on herbivorous insects: linking multiple herbivore species on a willow

Abstract: We experimentally examined the effects on other herbivorous insects of leaf shelters constructed by lepidopteran larvae on a willow, Salix miyabeana. Several insect species occupied the vacant leaf shelters. Our experiment using artificial leaf shelters showed that the number of aphids increased with the number of artificial leaf shelters on a shoot, as did the numbers of three ant species (Camponotus japonicus, Lasius hayashi, and Myrmica jessensis) that entered leaf shelters to collect aphid honeydew. To determine the ant-mediated effect of leaf shelters on herbivorous insects that do not use leaf shelters, we transferred newly hatched larvae of a common leaf beetle, Plagiodera versicolora, to the leaves of shoots with and without artificial leaf shelters. One day after the transfer, larval survival rate was significantly lower on shoots with shelters than on those without shelters, and shoots with shelters had significantly more ants than did shoots without shelters. Our field experiments demonstrated clearly that shelter-making lepidopteran larvae increased the abundance of both aphids and ants and decreased the survival rate of leaf beetle larvae, probably because the larvae were removed by ants that were attracted to the leaf shelters by the aphid colonies.

Bodyguard effects for aphids of Aphis craccivora Koch (Homoptera: Aphididae) as related to the activity of two ant species, Tetramorium caespitum Linnaeus (Hymenoptera: Formicidae) and Lasius niger L. (Hymenoptera: Formicidae)

Abstract: Laboratory experiments were carried out to clarify the bodyguard effects for the aphid, Aphis craccivora Koch, against predatory ladybeetle larva, Coccinella septempunctata L., by two ant species, Tetramorium caespitum Linnaeus and Lasius niger L. In particular, we examined the effectiveness of protection for aphids as related to ant activities on a plant. The number of attacks on a ladybeetle larva by ants until the ladybeetle larva dropped from the plant did not differ between the two ant species, suggesting similar aggressiveness of the two ant species. However, the number of attacks per min by L. niger was five times greater than that by T. caespitum. Consequently, the residence time of the ladybeetle larva was shorter and the proportion of aphids eaten was lower in the presence of L. niger than in the presence of T. caespitum. Thus, the encounter rate between ants and predators is one of the most important factors for bodyguard effects on aphids, resulting from the markedly different foraging behaviors of the two ant species.

Effects of experimental small‐scale grassland fragmentation on spatial distribution, density, and persistence of ant nests

Abstract: Ameisen im Untersuchungsgebiet Nenzlinger Weide 1 Grassland fragmentation is expected to influence the abundance of different invertebrate species to a different extent Fragmentation-related effects are of particular importance in species that interact with many other species 2 The density and spatial distribution of nests of 15 ant species in experimentally fragmented calcareous grasslands at three sites in the Northern Swiss Jura mountains were examined Fragments of different size (025 m(2), 225 m(2), and 2025 m(2)) were isolated by a 5-m wide strip of frequently mown vegetation Control plots of corresponding size were situated in adjacent undisturbed grassland 3 Three years after initiation of the experiment, ant nest density did not differ between fragments and control plots Six years after initiation of the experiment, however, ant nest density and forager abundance were higher in large fragments than in large control plots Ant nests tended to occur more frequently along the edge of fragments than in the core area Persistence time of nests of the most abundant species, Lasius paralienus, tended to be shorter in fragments than in control plots Furthermore, persistence time was longer in nests situated close to the fragment edge than in nests in the core area 4 Effects on nest density, edge effects on the spatial distribution of nests, and the relationships between nest density and environmental factors were more pronounced when only nests of L paralienus were considered The implications of these findings for plant and other invertebrate species are discussed

Changes in the Use of Extrafloral Nectaries of Vicia faba (Leguminosae) and Honeydew of Aphids by Ants with Increasing Aphid Density

Abstract: To elucidate how ants use two simultaneously present food resources, honeydew and extrafloral nectary (EFN), in relation to aphid density, we first examined ant recruitment patterns with different densities of aphids on Vicia faba L. (Leguminosae) with EFN in two field sites with different species composition of ants. Three species of ants visited plants of V. faba at each site, but two different species, Tetramorium caespitum Linnaeus (Hymenoptera: Formicidae) and Lasius niger L. (Hymenoptera: Formicidae) were the main visitors on plants of V. faba at the different sites. The numbers of ants of T. caespitum and L. niger visiting a plant increased as the density of Aphis craccivora Koch (Homoptera: Aphididae) per plant increased. The correlation between the numbers of L. niger and Aphis craccivora was higher than that between the numbers of T. caespitum and A. craccivora. Second, we examined in a laboratory how two ant species, T. caespitum and L. niger, use the honeydew of A. craccivora and V. f...

The relationship between multiple mating by queens, within-colony genetic variability and fitness in the ant Lasius niger

Abstract: Multiple mating has been suggested to benefit social insect queens because high genetic variation within colonies might decrease the load imposed by sterile diploid males, enhance resistance to parasites and pathogens, and lead to a more effective division of labour and/or a wider range of tolerable environmental conditions. We tested these hypotheses in the ant Lasius niger with three population samples from Switzerland and Sweden. We found no diploid males in young or mature colonies suggesting a lack of diploid male load. Colonies with multiply-mated queens were not larger nor did they produce more sexuals than colonies with singly-mated queens. We did find a significantly lower frequency of multiple mating among newly mated queens than among the queens heading mature colonies in one population sample (Switzerland 1997). However, this result was not repeated in the other study population, or in the following year in the Swiss population.

Dispersal of the lycaenid Plebejus argus in response to patches of its mutualist ant Lasius niger

Abstract: We examined the movement rates of individuals of an obligate myrmecophilous butterfly, Plebejus argus (Lycaenidae: Lepidoptera), in relation to a patch of its mutualist ant, Lasius niger. Marked male and female P. argus from local (resident), fragmented and continuous populations were released into and away from ( > 100m) a patch of L. niger, and subsequently searched for in a 500 x 500 m area. Recaptures of males and females from all populations were strongly associated with the target patch of mutualist ants. First day recapture displacements were significantly higher for releases away from the target patch for males, but not for females. Mutualist ant presence was shown to be more important than nectar source density in determining persistence of P. argus in release squares. There was no significant difference in displacement distances or recapture frequencies (standardised for search effort) in the target patch of individuals from local (resident of target patch), fragmented and continuous populations. The recapture frequency in the target patch of males from the local population released outside the target patch was greater than expected from a null model of random straight line movement, suggesting non-random (systematic or orientated) search behaviour. The number of males remaining in the target patch following release into the target patch was greater than expected from a simple diffusion model, suggesting a behavioural response to patch boundaries or other cues related to the patch.

Impacts of two ants, Lasius niger and Pristomyrmex pungens (Hymenoptera : Formicidae), attending the brown citrus aphid, Toxoptera citricidus (Homoptera : Aphididae), on the parasitism of the aphid by the primary parasitoid, Lysiphlebus japonicus (Hymenoptera : Aphidiidae), and its larval survival

Abstract: The brown citrus aphid, Toxoptera citricidus, was attacked by the parasitoid Lysiphlebus japonicus, and was actively attended by two ant species, Lasius niger and Pristomyrmex pungens. The impacts of the two ants on the parasitism of the aphid by the parasitoid were assessed experimentally at a no-pesticide mandarin grove. Aphid colonies were artificially initiated on young citrus shoots in summer. Lysiphlebus japonicus females were frequently observed foraging in aphid colonies attended by P. pungens, but rarely in colonies attended by L. niger and colonies where ants were excluded. L. japonicus females were attacked by P. pungens workers, but oviposited successfully by avoiding the ants. Large predators were excluded by both ant species from the aphid colonies, while they were abundant in ant-excluded colonies. L. niger workers often carried living aphids away from the attended colonies, whereas P. pungens removed no aphids and disregarded parasitized aphids, thereby incidentally protecting the parasitized aphids from predators. Consequently, L. japonicus-mummies were formed in great numbers in colonies attended by P. pungens, but were scarce in colonies attended by L. niger and ant-excluded colonies. Aphid-attending P. pungens workers reduced predation and hyperparasitism on L. japonicus larvae within mummies. Thus, P. pungens attending T. citricidus largely enhances parasitism by L. japonicus and its larval survival, compared with when ants are absent, whereas L. niger exerts no remarkable impact.

Polymorphic microsatellite markers for the ant Plagiolepis pygmaea

Abstract: Detailed studies on kin structure, mating patterns and dispersal in social insects require highly polymorphic markers, of which the most commonly used today are DNA microsatellites. Here we characterize 10 polymorphic microsatellite markers for the ant Plagiolepis pygmaea. We also investigated the within-genus applicability of the markers on P. xene, a social parasite of the source species. In addition, we tested amplification of the markers in three species of the genera Formica and Lasius. Eight of the markers also amplified in P. xene and were polymorphic. Seven markers amplified in at least one other formicine ant.

Microgeographical distribution of ants (Hymenoptera: Formicidae) in coastal dune grassland and their relation to the soil structure and vegetation

Abstract: In this paper, we investigate the microgeographical distribution of ants nests in an intensively grazed dune pasture. A total of seven species were recorded. By the application of a forward multiple logistic regression we were able to determine nesting choice for the three common species Lasius niger, L. psammophilus and Myrmica specioides . The e rst could be identie ed as a pioneer species, while the two latter species, which are typical of dry, sandy dune grounds, differ slightly in their nesting preference. The effect of nest building on soil structure was investigated for a mound-building species ( Formica cunicularia) and for a non-mound-building species ( Lasius psammophilus ). Both species signie cantly decrease the thickness of the organic and water-capturing soil layer, while the mound-building species additionally affects the soil lime content (an increase) and the soil hardness (a decrease). Mound building in dense Calamagrostis vegetation also stimulates the germination of a characteristic and rare plant species, Thymus pulegioides .

Queen control over reproductive decisions — no sexual deception in the ant Lasius niger

Abstract: Queen-worker conflicts in social insect societies have received much attention in the past decade. In many species workers modify the colony sex ratio to their own advantage or produce their own male offspring. In some other species, however, queens seem to be able to prevent workers from making selfish reproductive decisions. So far, little effort has been made to find out how queens may keep control over sex ratio and male parentage. In this study we use a Lasius niger population under apparent queen control to show that sexual deception cannot explain queen dominance in this population. The sexual deception hypothesis postulates that queens should prevent workers from discriminating against males by disguising male brood as females. Contrary to the predictions of this hypothesis, we found that workers are able to distinguish male and female larvae early in their development: in early spring workers generally placed only either female or male larvae in the uppermost chambers of the nest, although both types of larvae must have been present. At this time males were only at 11% of their final dry weight, a developmental stage at which (according to two models) workers would still have benefited from replacing queen-produced males by females or worker-produced males. This study thus demonstrates that sexual deception cannot account for the apparent queen control over colony sex ratio and male parentage in L. niger.

Further record of Lasius neglectus Van Loon, Boomsma et Andrasfalvy (Hymenoptera: Formicidae) for Warsaw, with a key to the Polish species of the subgenus Lasius s. str.

Abstract: Three new sites of Lasius neglectus, an expansive invasive polygynous and polydomous ant species, are reported from Warsaw, its northern most known locality. A key to the Polish representatives of the subgenus Lasius s.str. is given.

Discrimination of Aphid Mutualists by an Ant Based on Chemical Cues

Abstract: A chemical basis for discrimination between attended and unattended aphid mutualists by the ant Lasius niger (L.) (Hymenoptera, Formicidae) was investigated. In an arena bioassay, hexane extracts of the aphid Rhopalosiphum padi (L.) (Homoptera, Aphididae), which had been attended by the ant colony provoked significantly longer examination by ants than extracts of unattended aphids. Extracts of the ants themselves were significantly more active than hexane. In an olfactometer, ants spent significantly longer in the arm containing the odour of live aphids that had been attended by the ants than in arms containing the odour of unattended aphids. When unattended aphids were introduced onto an aphid-infested plant under attendance by L. niger, they suffered higher levels of attack and removal by the ants than did previously attended aphids. Unattended aphids treated with the extract of attended aphids suffered higher levels of attack than attended aphids, but lower levels of removal than unattended aphids. The...

First description of the worker caste of Lasius viehmeyeri Emery (Hymenoptera: Formicidae)

Abstract: Up till now the worker caste of Lasius viehmeyeri was unknown. In the Starcke Collection present in the Nationaal Natuurhistorisch Museum at Leiden, a worker of L. viehmeyeri was discovered under Lasius umbratus var. affinis Schenck. This specimen from Dalmatia is described and figured.

The temporary social parasite lasiu s bicornis (förster, 1850) new to slovenia, and m yrm ica bessarabica nassonov, 1889 corrected into m specioides bondroit, 1918 (hymenoptera: formicedae)

Abstract: The Western Palaearctic ant Lasius (Chthonolasius) bicornis (Forster, 1850) is reported for Slovenia for the first time. The temporary social parasite is very rare species throughout its distribution range. The presented record originates from a decidous forest aside a small brook, which sporadically inundates the site. This type of habitat was so far unknown to be inhabited by L. bicornis. Due to recent tax­ onomic changes, Myrmica bessarabica Nassonov, 1889, listed for Slovenia by Bracko (2000) must be substituted by M. specioides Bondroit, 1918. K e y w o r d s : ants, faunistics, Lasius bicornis, Myrmica specioides, Slovenia. Izvlecek ZACASNI SOCIALNI PARAZIT LASIUS BICORNIS (FORSTER, 1850), NOVA VRSTA ZA SLOVENIJO, IN MYRMICA BESSARABICA NAS­ SONOV, 1889, POPRAVLJENA V M. SPECIOIDES BONDROIT, 1918 (HYMENOPTERA: FORMICIDAE) Zahodnopalearkticna mravlja vrste Lasius (Chthonolasius) bicornis (Forster, 1850) je bila prvic najdena v Sloveniji. Ta zacasno socialno parazitska vrsta je pre­ cej redka na celotnem obmocju njene razsirjenosti. Najdena je bila v listnatem gozdu 159 ©Slovenian Entomological Society, download unter www.biologiezentrum.at Acla entomologica slovenica, 11 (2), 2003 blizu majhnega potoka, ki obcasno poplavlja okolico. Do sedaj se ni bilo znano, da bi vrsta L. bicornis prebivala v takem habitatu. Zaradi novejsih taksonomskih spre­ memb je potrebno vrsto Myrmica bessarabica Nassonov, 1889, ki je navedena v sez­ namu za Slovenijo (Bracko 2000), zamenjati z M. specioides Bondroit, 1918. KLJUCNE BESEDE: mravlje, favnistika, Lasius bicornis, Myrmica specioides, Slovenija. The twelve European species of the subgenus Chthonolasius are temporary social parasites. Hosts are species of the subgenus Lasius s.str. (Seifert 1988a) and pre­ sumably species of Cautolasius (Schlick-Steiner et al. 2002). Like social parasites in general, Chthonolasius species have much lower densities than their hosts (Buschinger 1971). Their hypogaeic life habit (Seifert 1996) makes them difficult to be found. Furtheron, the determination of some of the species remains one of the most difficult tasks within European ants. These aspects result in a general scarce­ ness of data on faunistics, ecology and biology (Seifert & Buschinger 2001). From 5 June to 12 July 2001, pitfall traps were exposed in a Quercus petraeaCarpinus betulus forest aside the small, strongly meandering brook Virje at Dobrava, NE of Brežice (Slovenia, 45°56’N/15°40’E, 160 m a.s.l.). The crown closure was high, the herbaceous layer was weak with little patches of direct light reaching the ground. The soil was sandy, with local patches of clay. Rotten wood was present, but its density was low. The water regime was highly dynamic during the trapping peri­ od: A strong inundation flooded the pitfall traps in early June, but already at the end of June the brook was completely drained and the stand had a dry-warm appearance. The catches contained a single worker of Lasius (Chthonolasius) bicornis (Forster, 1850). Cooccurring ant species were Myrmica rubra (Linnaeus, 1758), M. specioides Bondroit, 1918, Leptothorax crassispinus Karawajew, 1926, Myrmecina graminicola (Latreille, 1802), Stenamma debile (Forster, 1850), Lasius platythorax Seifert, 1991, Formica gagates Latreille, 1798 and F. fusca Linnaeus, 1758. In Bracko (2000) Myrmica specioides had been referred to as Myrmica bessarabica Nassonov, 1889, which was recently classified as „Myrmica incertae sedis“ (Seifert 2002); the characters of M. specioides according to Seifert (1988b) and Seifert (1996), do however apply to all records of “M bessarabica” in Bracko (2000). Lasius bicornis has a Western Palaearctic distribution (Seifert 1988a), but is a very rare and only locally occurring species throughout its range (Seifert 1996). The species nests in rotten logs of dead and living trees (Seifert 1988a), and occasional­ ly in the ground (Mei 1984, Seifert 1988a). Little is known about the feeding habits of L. bicornis, but once the lachnid Schizodryobius pallipes Hartig, obviously a trophobiotic partner, was found inside a nest (Mei 1984). No direct observation of a host use by L. bicornis has been accomplished by now, but Lasius brunneus (Latreille, 1798) is the most probable host (Seifert, unpublished data). Determination of all castes, as an exception within Chthonolasius, is comparatively easy and unequivocal (Seifert 1988a). From an ecological point of view this record of L. 160 ©Slovenian Entomological Society, download unter www.biologiezentrum.at B. C. Schlick-Steiner, F. M. Steiner, G. Bracko, W Paill. B. Seifert: The temporary social parasite Lasius bicornis (Forster, 1850) bicornis is interesting, as the species has so far not been found in a sporadically indundated habitat. In faunistic respect the record is not surprising as L. bicornis occurs in the countries neighbouring Slovenia, for which recent faunistic data are available, i.e. Italy (Poldi et al. 1995), Hungary (Galle et al. 1998) and Austria (Steiner et al. 2003).