Second species in the Australian ant genus Peronomyrmex Viehmeyer (Hymenoptera: Formicidae)

A second species of the rare Australian ant genus Peronomyrmex is described from Victoria. This new species, P. bartoni , represents only the third time the genus has been collected, the previous records being the holotype of P. overbecki Viehmeyer from north-eastern New South Wales and a collection, subsequently lost, from northern Queensland.     

Polynesian ant (Hymenoptera: Formicidae) species richness and distribution: a regional survey

Thirteen Polynesian islands, including five true atolls, an uplifted atoll, and seven high volcanic islands of varying ages, were surveyed for ants by hand collecting techniques. Ten of the thirteen islands had been surveyed previously, and more and species were found in the present survey than were known from all earlier surveys combined, with two exception (Ducie Atoll and Easter Island).This represents the first report of the Argentine ant, Linepithema humile Mayr, from Easter Island. L. humile is a very successful pest species which has only recently invaded Easter Island, and is now very abundant and widespread, occurring at 16 of the 17 sample sites scattered across the island. The introduction of this species is almost certainly responsible for the apparent decline in species richness on Easter Island.In general, more species were present on high islands than atolls of a similar size, and elevation was significant while log (area) and latitude were not in a multiple linear regression with ant species number as the dependent variable. Not enough time was spent on the islands to survey their ant faunas completely, and extrapolations from species effort curves and jackknife estimators of earlier, thorough surverys for ants in the society Islands suggest that only about 50% of the total species were collected in the present survey, at least on the high islands. My collections were probably more complete on the atolls. The increase in species numbers from the present survey relative to known species richnesses (particularly when a large fraction of the species actually present were probably not included in the present survey) supports the hypothesis that remote Polynesian islands are not as depauperate in terms of ant species numbers as previously thought.     

Trail-following responses ofTapinoma simrothi (Formicidae: Dolichoderinae) to pygidial gland extracts

Summary The pygidial (anal) gland was found to be the source of trail pheromone in the antTapinoma simrothi. Bioassays conducted with fractionated pygidial gland secretion indicated that the fraction containing iridodials and iridomyrmecin is responsible for the trail pheromone activity. Thus workers ofT. simrothi may utilize the same glandular exudate for alarm and trail following. At high emission rates from a point source, the ants responded in alarm, e.g., rushed to the source with open mandibles and raised abdomen. When concentrations were low and drawn as a line, the ants followed the secretion calmly. Trails ofT. simrothi are long-lived, having a biological half-life of 10 to 19 days. Quantitative studies of the evaporation rates of the iridodials by gas chromatography resulted in a half-life of 11 days, agreeing with the biological data. The implications of the use of the same glandular secretion for alarm and food recruitments are discussed.     

Mechanisms affecting load size determination inAtta cephalotes L. (Hymenoptera,Formicidae)

Summary The size of leaf-cutting ant foragers correlates more closely with the weight than the area of the leaf fragments they cut. This implies that the mechanism of load size determination is not a simple function of body geometry. Ants were found not to adjust the radius of cut to compensate for experimental changes in leaf weight during the process of cutting. However, ants changed their cutting behaviour according to the thickness of the region of the fragment being cut. Ants decreased their cut radius when cutting through leaf veins. Similarly, when cutting artificial laminae of varying thicknesses, ants reduced the cut arc radius when traversing thicker regions.Cut radius was not principally controlled by the position of the rear legs nor the overall body length but by mechanisms associated with the head and thorax of the ant.     

Ontogeny of queen attraction to workers in the antCataglyphis cursor (Hymenoptera: Formicidae)

Summary The behaviour ofCataglyphis cursor workers towards queens at 15 days, one month or two months after worker emergence was tested. Workers reared entirely with their own maternal queen were tested with this queen or with an unfamiliar alien queen. Workers transferred within 48 h of emerging to a new definitive nest with an alien queen were tested with this queen or with the original maternal queen. The degree of attraction to each of these queens and the workers' behavioural repertoire were measured and analysed. The results showed the following: 1) The attractiveness of queens and the workers' queen recognition behaviour were linked. 2) Although unfamiliar alien queens hardly attract workers, familiar alien queens were as attractive as maternal queens, and induced the same strongly marked and unique worker response, indicating that workers learn queen attractant cues in the days immediately after emergence. 3) Agonistic reactions were observed, but workers continued to be attracted to their maternal queen even after developing an attraction response to an alien queen with which they had been reared. These results agree with the proposal that queens produce two kinds of pheromones, those that attract workers and those that mediate recognition of queens by workers. These results show the ability of workers to discriminate between queens. Workers are attracted to any queen, but recognize as nestmates only maternal or alien queens with which they have been maintained. 4) The differential in worker attraction and recognition from 15 days to 2 months and its modifications by post-imaginal experience illustrate worker behavioural ontogeny, which is a basis of social discrimination.     

Frequent occurrence of gynandromorphs in the natural population of the antVollenhovia emeryi (Hymenoptera: Formicidae)

Summary Many gynandromorphs were obtained from the natural population ofVollenhovia emeryi (microgyna form) in Gifu, Japan. They were primarily male: most had the thorax and gaster of males, and the head contained tissues partially feminized to varying degrees. These gynandromorphs were found in 27 of 45 colonies studied (60.0%). Their proportion to total males in each colony varied from 3.7–47.7%, with a mean of 21.4% (n = 21). The gynandromorphs were found in all study areas and in every study year, suggesting that gynandromorphism in this species is not a rare phenomenon. Moreover, this observation suggests that gynandromorphs may occur more frequently in micraners than in macraners.     

Spatial specialization of the foragers and foraging strategy inLasius fuliginosus (Latreille) (Hymenoptera,Formicidae)

Summary The spatial specialization inLasius fuliginosus was investigated in the field by a mass-marking of foragers with colors. In the spring, summer and autumn, foragers exhibit a high degree of persistence, with coefficients of fidelity between 83 and 96%, in using a particular foraging trail, in visiting a particular tree or shrub housing aphid colonies, and even micro-sites like a particular branch. A high degree of fidelity to particular temporary hunting ground areas has also been shown. Trail and aphid site fidelity persist for at least 1 to 3 months and are preserved through the hibernation period (about 5 months). However, in early spring, a period during which food sources are scarce, trail fidelity is lower (coefficient of fidelity: 57%).Spatial specialization develops quickly in foragers recruited to a new permanent food source. Once acquired, the specialization is not rigid since specialized honeydew collectors can shift from a no more rewarding aphid site to other aphid sites of the same trail on which they develop a secondary specialization.The ecological and behavioral aspects of the spatial specialization inL. fuliginosus are discussed with reference to the resource structure of the habitat.     

Biology and myriapod egg predation by the Neotropical myrmicine antStegomyrmex vizottoi (Hymenoptera: Formicidae)

Summary For the first time for a Neotropical ant and for Myrmicinae, the searching behavior and specialized predation of spirobolid millipede eggs byStegomyrmex vizottoi Diniz will be described. The relationship between morphology and habits is studied, as are nest architecture and distribution of the ant population in the nest chambers. We also report on some observations of behavior in the field and laboratory.We dedicate this paper to William L. Brown Junior, on the occasion of his 70^th birthday.     

The ant-tribe Leptothoracini in Turkey (Hymenoptera,Formicidae)

Abstract

A review is given of the state of knowledge of the 16 or more species of the ant tribe Leptothoracini that are known to occur in Turkey, together with a map of the published records and a list of new finds.     

Pine plantations in south eastern Australia support highly impoverished ant assemblages (Hymenoptera: Formicidae)

Pitfall trap surveys of ants were undertaken in mature and intermediate-aged Pinus radiata plantations and parental eucalypt forest in central Victoria, Australia. Ant assemblages of pine plantations are an impoverished subset of the eucalypt forest assemblages. Very few ant morphospecies, most of them in very low abundance, were found in unthinned intermediate-aged pines, and the numbers were substantially higher in older, thinned pines in which understorey vegetation is considerably more developed. Implications for plantation management and conservation of epigaeic ant assemblages are discussed.     

The Effect of Food Size and Dispersion Pattern on Retrieval Rate by the Argentine Ant, Linepithema humile (Hymenoptera: Formicidae)

Food acquisition in central-place foraging animals demands efficient detection and retrieval of resources. Most ant species rely on a mass recruitment foraging strategy, which requires that some potential foragers remain at the nest where they can be recruited to food once resources are found. Because this strategy reduces the number of workers initially looking for food, it may reduce the food detection rate while increasing the postdiscovery food retrieval rate. In previous studies this tradeoff has been analyzed by computer simulation and mathematical models. Both kinds of models show that food acquisition rate is greatly influenced by food distribution and resource patch size: as food is condensed into fewer patches, the maximal acquisition rate is achieved by a shift to fewer initial searchers and more potential recruits. In general, these models show that a mass recruitment strategy is most effective when resources are clumped. We tested this prediction in two experiments by letting laboratory colonies of the Argentine ant (Linepithema humile) forage for resources placed in different distributions. When all prey were small, retrieval rate increased with increasing resource patch size, in support of foraging models. When prey were large, however, the mass of prey returned to the colony over time was much lower than when prey were small and widely distributed. As more ants reached a large prey item, the distance the prey item was transported decreased due to a greater emphasis on feeding rather than transport. Because Argentine ants can transport more biomass externally than they can ingest, food retrieval that depends only on ingestion can depress the biomass retrieval rate. Thus, our results generally support theoretical foraging models, but we show how prey size, through differential prey-handling behavior, can produce an outcome greatly different from that predicted only on the distribution of resources.     

The Substrate Vibration Generating Behavior of <Emphasis Type="Italic">Aphaenogaster carolinensis</Emphasis> (Hymenoptera: Formicidae)

Aphaenogaster carolinensis Wheeler produces substrate vibrations by striking a substrate with its mandible and dragging its mandible across the surface. We have described this behavior and conducted laboratory trials to isolate some of the conditions under which it may occur. Individual strikes were consistent in pattern and duration, but there was great variation in the duration of, and the number of strikes associated with, a single substrate vibration generating event. In laboratory trials, this behavior occurred most frequently in response to confrontation with non-nest mate con-specifics and did not require the presence of a food source or colony territory to be initiated.     

Arboreal search in ants: Search on branches (Hymenoptera: Formicidae)

Ants (Formicidae) perform two distinct search behaviors for resources: on the ground they use irregular, almost random alternating looping, and on branches and leaves they resort to outline-tracing (arboreal systematic search), whereby the individual systematically turns to one side at bifurcations and to the opposite side when turning about at end points. Experiments with searching Formica pallidefulva and Crematogaster cerasion artificial stick mazes under seminatural conditions demonstrated that bifurcations and end points only trigger turn decisions, whereas an intrinsic mechanism specifies the handedness of such turns. Arboreal homing differs from arboreal searching by a much stronger tendency to rectify paths by counterturning. The theory is advanced that searching on branches by outline-tracing is evolutionarily derived from ranging search by superposing a sustained intrinsic turn bias and by suppressing random turns.     

Pitfall trapping for ants (Hymenoptera,Formicidae) in mesic Australia: the influence of trap diameter

Catches of ants in the two most commonly-used forms of pitfall trap (‘test-tube’ traps, ca 18 mm diameter; ‘coffee cup’ traps, ca. 70 mm diameter) are compared from samples in open grassy woodland in southern Victoria, Australia. The 25 morphospecies found in the narrower traps were all represented among the 31 morphospecies collected in the larger traps. Either pattern is adequate to collect samples for broad inter-treatment comparisons and documentation of the more typical and representative fauna, but larger traps may have some advantage if more complete inventory is sought.     

Labial gland disease in the genusFormica (Formicidae,Hymenoptera)

Summary Labial gland disease causes swelling of the labial glands in the pupal stage inFormica species. The resulting adults have enlarged thoraces and are called secretergates (Wasmann's pseudogynes). They infect the younger larvae, probably during feeding. The agent of the disease is unknown. It soon becomes non-infectious outside the labial glands. Diseased females were not seen to feed larvae. Yet their offspring contained secretergates. The discrepancy remains unexplained.     

Eleven microsatellite loci in the sociobiologically enigmatic ant Lasius austriacus (Hymenoptera: Formicidae)

We describe the isolation and characterization of 11 microsatellite loci in the sociobiologically enigmatic ant Lasius austriacus. The polymerase chain reaction primers were tested on a population in East Austria. The number of alleles ranged from four to 19 and the observed heterozygosity from 0.200 to 0.900. Cross‐species amplification tests were performed, with some loci polymorphic in all species tested, for the closely related invasive species Lasius neglectus, three further Lasius species, another formicine, Formica polyctena, and the invasive myrmicine species Tetramorium tsushimae.     

Trophic eggs laid by fertileMyrmica queens (Hymenoptera: Formicidae)

Summary Most matureMyrmica rubra, M. ruginodis, M. schencki andM. sulcinodis queens lay some trophic eggs in addition to reproductive eggs whether reared alone or attended by workers, and regardless of season. Queen trophic eggs resemble those laid by workers. They are oval, slightly flaccid, opalescent and contain no embryo, and inM. rubra andM. schencki they are significantly smaller than reproductive eggs. Generally, queens lay their first trophic eggs later in the season than their first reproductive eggs.     

Further records of ants (Hymenoptera: Formicidae) from Iran

Wide ranging surveys of the ant fauna of Iran have enabled us to add a further 30 named species to the country list. A review of almost all the published literature and of photographs of unidentified specimens within the public domain gives a grand total of 248 species, from seven subfamilies and 37 genera. In the majority of instances, our own specimens were compared with type images available from antweb.com. This has led us to propose new or revised status for Cataglyphis turcomanica Crawley 1920, Lepisiota integrisquama (Kuznetsov-Ugamsky, 1929), Lepisiota surchanica (Kuznetsov-Ugamsky, 1929) and Messor obscurior Crawley 1920. We note that the total includes a number of what may be misidentifications and a small number of named species that seem unlikely to occur in Iran.     

Phylogeny and bionomics of Lasius austriacus (Hymenoptera,Formicidae)

Summary Phylogenetic analysis based on sequence data of the mitochondrial COI gene confirms the species status of the recently described Lasius austriacus. The five haplotypes of L. austriacus do not cluster according to their geographic origin, indicating a recent gene flow among the populations. The molecular data corroborate the morphology based hypothesis that L. austriacus belongs to the Lasius (Lasius s.str.) brunneus group. The invasive species Lasius neglectus forms a sister taxon with L. turcicus, both next related to L. austriacus. Other phylogenetic relationships within the genus Lasius are in accordance with morphological data.First data on the bionomics of L. austriacus are discussed in context with its phylogenetic position. Based on gyne and male morphology, excavations of nests, pitfall trapping and observations in formicaries, we hypothesize that L. austriacus is a mainly hypogaeic, monogynous species with nuptial flight. These are characters of the Lasius brunneus group in general, except the polygynous-polycalic, intranidally copulating L. neglectus. Aggression tests, however, revealed non-aggressive behaviour (antennation) between separated L. austriacus populations, but pronounced interspecific aggression against L. neglectus. This confirms the species status of L. austriacus and indicates a reduced level of intraspecific aggression, similar to L. neglectus.The status of L. austriacus as a native species in Central Europe is confirmed.Received 10 February 2003; revised 24 June 2003; accepted 23 July 2003.