Respiration during the metamorphosis of sexuals in Lasius flavus (Hymenoptera, Formicidae)

ABSTRACT. The respiration of metamorphosing gyne Lasiusflavus Fab. has been measured in field and laboratory populations. Twelve morphological stages are identified and their respiratory rate investigated. Only five physiological phases are distinguished. The specific respiratory rate varies between these phases, to produce the U-shape characteristic of insects. There is good agreement between the data from English field and Danish laboratory populations. The minimum rate is only 40% of the maximum. Except at the beginning and end of metamorphosis, the Q₁₀ is significantly different in the two temperature intervals 10–20 and 20–30C. Metamorphosis was completed in approximately 33 days at 20C. The total oxygen consumption by the gynes during metamorphosis was 2.4 ml. Their weight loss amounted to 2.2 mg, or 36% of the dry weight and, of this, 0.67mg was accounted for by fat. Assuming the rest was carbohydrate, consumption of these reserves would release 62.9 J, which, for this combination of fat and carbohydrate, can be calculated to be equivalent to 3.1 ml oxygen which is in reasonable agreement with the figure calculated from the measurement of oxygen consumption. The specific respiratory rate in English field populations of male pupae varies in the same way as the gyne-pupae, but it is about 50% higher.     

Regional trends and preliminary results on the local expansion rate in the invasive garden ant, <Emphasis Type="Italic">Lasius neglectus</Emphasis> (Hymenoptera,Formicidae)

The expansion process of the invasive garden ant, Lasius neglectus in Europe and Asia is described in terms of: a) local expansion through colony growing measured on four supercolonies (Seva, Debrecen, Buda Castle and Budatétény) from two distant and climatically different countries (Spain, Hungary), and b) regional expansion, using data from all published and several new non-native localities. Short, local distance processes (few meters to 89 m year-¹), as colony budding, are two to five orders of magnitude smaller than long regional distances (ten km to >1000 km). This suggests direct human intervention in the invasive spread. The regional trend also shows that the invasive garden ant has been quickly and steadily increasing the number of non native localities (77) and countries (14) it has reached during the last 30 years. Received 2 January 2006; revised 17 May 2007; accepted 1 June 2007.     

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.     

Dynamics of aggregation in <Emphasis Type="Italic">Lasius niger</Emphasis> (Formicidae): influence of polyethism

Summary Polyethism is a well-known phenomenon in social insects. How this phenomenon influences interactions among individuals, the spatial distribution in the nest is, on the other hand, very rarely documented. Therefore, we conducted experiments on the ant Lasius niger to observe the influence of polyethism on aggregation, by distinguishing two groups of ants: the brood-tenders and the foragers. We show a great difference in their self aggregation level. Brood-tenders are characterized by a rapid and dense gathering in one main stable cluster while foragers gather in several small unstable clusters. We show experimentally and verify with a model that this difference in behaviour is based on a smaller probability of leaving a cluster for the brood-tenders. Aggregation in the mixed case (groups composed of brood-tenders and foragers) is very close to that of the pure forager case, showing a decrease in the level of aggregation of the brood-tenders respecting to the pure group of brood-tenders. Nevertheless, experimental results supported by the results of the model, show that ants do not change their own behaviour when the two groups are together. Therefore, the decrease of the aggregation of brood-tenders in the mixed case can be explained by a difference in the dynamics between brood-tenders and foragers.Received 9 May 2003; revised 26 August 2003; accepted 1 September 2003.     

Dynamics of Nest Excavation and Nest Size Regulation of Lasius niger (Hymenoptera: Formicidae)

The adaptation of nest size to its population is one of the most common processes, but little is known about the dynamics nest-building and -enlarging in social context. Furthermore, the mechanisms involved remain totally ignored. We present here the first results of such dynamics in the context of Lasius niger's nest excavation. We find, with an artificial but standardized method, a strong positive correlation between the number of ants and the final nest volume as well as the digging rate. Both grow almost proportionally to population. When the number of individuals is artificially increased (even slightly) in a nest, its dimension is systematically adjusted in the same way as initial excavation. In this process, digging acts as a negative feedback that controls nest enlargement. Experiments revealed that this negative control is due directly to the volume of the nest as well as the physiological or behavioral modification of ants after digging. Finally, amplification of activity was observed during the enlargement phase, suggesting the possible implication of self-organized processes in the volume control mechanism.     

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.     

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.     

Queen number in a supercolony of the invasive garden ant, <Emphasis Type="Italic">Lasius neglectus</Emphasis>

Summary We have analysed the distribution of queens under stones at the core and at the periphery of a supercolony of Lasius neglectus that occupies 14 ha at Seva (NE Spain). Queens were not found alone, but rather within worker groups. Density at the center (mean ± s.d.: 1.38 ± 2.87 queens/stone; n = 100 stones; range 0–14) was not different from density at the periphery (1.18 ± 2.38; range 0–12). The estimate of the number of queens found under stones for the whole colony is about 35500. Egg-laying rates for queens from these two zones were obtained in the laboratory, at three different temperatures, and there were no differences detected. The presence of brood stages, from eggs to cocoons, was also similar in both zones. The homogeneous distribution of colony components may indicate that the area occupied by L. neglectus has already reached saturation. With a different technique – soil core extraction – we could estimate the density of workers in the soil: 800 workers per m². Soil cores had 6.28 ± 20.0 workers/core (range: 0–173), giving a rough estimate of 1.12 × 10⁸ workers in the soil, for the entire colony. Though few, some queens were also recovered from soil cores. Queen numbers for the supercolony, based on queens found in the soil, reaches the astounding level of 360000. Numbers are consistent with previous predictions.Received 10 September 2003; revised 1 December 2003; accepted 9 December 2003.     

Relationships between the ant Brachymyrmex obscurior (Hymenoptera, Formicidae) and Acacia pennatula (Fabaceae)

Summary. In central Mexico, the ant Brachymyrmex obscurior Forel feeds on nectar produced by extrafloral nectaries of Acacia pennatula (Schlecht. & Cham.) Benth. However, no studies have determined whether the ants visitation is related to plant nectar availability and whether ants protect A. pennatula from herbivory. The objectives of this 2-yr study (2000–2001) were to assess whether seasonal changes in ant visitation coincide with extrafloral nectar productivity in A. pennatula and to determine whether ants protect the plant. At the end of the dry season (April–June) B. obscurior was the only ant species on A. pennatula and extrafloral nectar production is limited to this period. Exclusion experiments, performed at the end of the dry season showed that A. pennatula did not receive a protective benefit when visited by ants. Branches with ants and branches where ants are excluded had similar numbers of the nonmyrmecophile leafhopper Sibovia sp. which was the only herbivore observed under natural conditions.Received 24 March 2004; revised 4 September 2004; accepted 8 September 2004.     

甘肃省毛蚁属一新种记述（膜翅目：蚁科：蚁亚科）

记述采自甘肃临夏地区的毛蚁属1新种-长须毛蚁Lasius longicirrus,sp.nov。模式标本保存在宁夏农学院标本室。     

Communication in the primitive cryptobiotic ant Prionopelta amabilis (Hymenoptera: Formicidae)

Summary The Neotropical ant Prionopelta amabilis, a cryptobiotic species in the phylogenetically primitive tribe Amblyoponini, lives in subterranean habitats, where it preys preferentially on campodeid diplurans and other small arthropods. Here we report that the species employs chemical recruitment and orientation trails during foraging and nest emigrations. The trail pheromone originates in a hitherto unknown basitarsal gland located in the basitarsus of the hindlegs. Trails are laid by a special foot dragging behavior. During the recruitment process the chemical trail signal is complemented by body shaking on the part of the recruiting ant. Foragers frequently wipe the basitarsal gland opening in the hindlegs with the grooming apparatus of the front legs. This latter structure is equipped with unusual glands evidently specialized for this purpose.     

Intraspecific slavery inPolyergus rufescens Latr. (Hymenoptera,Formicidae): field and laboratory observations

Summary Four intraspecific slave raids involving 3 colonies of the European amazon antPolyergus rufescens Latr. occurred during hot and sunny afternoons in July 1992 near Parma, Italy. Generally, no fighting between the resident ants and the invaders was recorded, and pillage of the brood lasted just a few minutes. The brood captured during 3 raids was collected and transported ot the laboratory where slavemaker callow workers eclosed and were accepted by both the raiders and hosts present in artificial mixed colonies. This is the first case of functional intraspecific slavery recorded in the field for the obligatory dulotic formicine antP. rufescens.     

Aggregation and adult transportation in disturbed colonies of <Emphasis Type="Italic">Wasmannia auropunctata</Emphasis> Roger (Hymenoptera,Formicidae)

Disturbance of W. auropunctata colonies first produced, as expected, significant dispersal of workers and queens, but this was soon followed by a radiate aggregation of workers, heads to center, in groups of 5 – 8 individuals, all with mandibles widely open. Queens did not aggregate, but instead searched for the grouped workers, antennating the gaster of a selected individual; after this, workers began to slowly board onto the queen’s body. This behavior was repeated with other groups, until the queen could not bear any more workers. This behavior is registered for the first time for adult ants, and is interpreted as a unique strategy to reorganize the nest or to establish a new colony. The open mandibles may indicate the release of alkylpyrazine, a known aggregation pheromone. Received 8 January 2007; revised 28 February 2007; accepted 2 March 2007.     

New synonymy of Proceratium williamsi Tiwari (Hymenoptera,Formicidae)

Proceratium bhutanense De Andrade, 2003, syn. n. is here found to be conspecific with Proceratium williamsi Tiwari, 2000 and accordingly treated as a junior synonym.     

Marking as a decision factor in the choice of a new resting site in <Emphasis Type="Italic">Lasius niger</Emphasis>

Summary In ants, aggregation is mainly based on the attraction between individuals. We confirmed the existence of ground marking in Lasius niger and demonstrated its influence on the aggregative behaviour of ants: the place of the gathering is leading by the existence of a ground marking which favours clustering by increasing the rate of the process but does not change the aggregation level. This factor could play a role in the choice of a new nest site and in the spatial distribution of ants inside the nest. This marking, presuming to have a long duration, could represent an external memory which could play an important role in various situations such as the choice of new nest or the reorganisation of ants after a disturbance.Received 23 July 2003; revised 16 December 2003; accepted 19 December 2003.     

Host nest usurpation and colony foundation in the European amazon ant,Polyergus rufescens Latr. (Hymenoptera: Formicidae)

Summary The socially parasitic mode of founding new colonies by queens of the European amazon antPolyergus rufescens was analysed in the laboratory. Newly-mated females of this obligatory slave-maker were individually introduced into queenright and queenless artificially established colonies of bothFormica cunicularia (the slave present in the natal dulotic nest) andF. rufibarbis (another potentialServiformica host). Particular attention was devoted to the behavioural patterns displayed by these young queens during the usurpation phases. Our observations, supported also by video-taping, show that the slave-making female, before laying her eggs, must penetrate the host colony, kill the resident queen, become accepted by the adult workers and appropriate the host brood. The parasite was almost always adopted in the colonies ofF. cunicularia, whereas in the presence ofF. rufibarbis it was generally killed in a short time. The failure in the attempt of usurping the colonies ofF. rufibarbis is discussed in relation to the host specificity typical of this slave-maker. Finally, egg-laying byPolyergus successful usurpers, the subsequent eclosion of the brood, and its complete social integration in the newly-established mixed colonies were also recorded.     

Seasonal cycle of colony structure in the Ponerine ant Pachycondyla chinensis in western Japan (Hymenoptera, Formicidae)

Investigation of reproductive strategies of ants in the subfamily Ponerinae is important for understanding of the evolution of social structure and of the significance of caste dimorphisms. The biology of species with mated and egg-laying workers (gamergates) has been studied for many species, however, little attention has been paid to species that reproduce via alate queens only. We investigated the seasonal cycle of changes in the colony structure of Pachycondyla chinensis reproduced by alate queens in western Japan, and found the following novel biological characteristics of this species. P. chinensis showed a remarkable caste dimorphism in ovariole numbers: workers had no ovaries while queens had 18 to 36 ovarioles in their ovaries. The nesting system seemed to be polydomous: 266 of 400 nests collected were queenless. The number of queenless nests increased during the reproductive season. Among the 134 queenright nests, 38 had several mated-queens without significant differences in ovary activation and the remaining 96 nests were monogynous. During winter to early spring, most nests were polygynous. After alate production, most of the old queens seemed to die or be expelled and replaced by new queens. Virgin dealated queens were often found and they seemed to have laid eggs. Received 3 August 2007; revised 19 December 2007; accepted 20 December 2007     

Respiratory patterns in nurses of the red wood ant Formica polyctena (Hymenoptera, Formicidae)

Summary Cycles of discontinuous gas exchange (DGCs) and abdominal ventilatory movements were studied in nurses of red wood ant, Formica polyctena, using an electrolytic respirometer and an infra-red (IR) gas analyser or flow-through respirometry. Both respirometry systems were combined with an IR actographic device based on IR-emitting and IR-sensor diodes. After recovering from handling and apparatus stress, lasting 1–3 h, completely motionless intact ants displayed regular DGC. After decapitation the ants displayed DGC whose frequency was somewhat lower than that of the intact individuals (7.17 ± 0.79 mHz and 10.43 ± 01.12 mHz, respectively). In headless ants, there occurred continuous slow movements of legs. Bursts of carbon dioxide in the intact and in the headless ants always coincided with a bout of telescoping movements (contractions) of abdominal segments, which was interpreted as active ventilation. During interburst periods, the headless ants exhibited telescoping movements characterised by rapid protraction, lasting 0.07–0.09 s, followed by a slow retraction of segments, suggesting passive ventilation. The intact ants were very sensitive to the flowing air and tended to be continuously active during flow-through respirometry. The decapitated ants, on the contrary, were insensitive to the air current.Received 26 March 2003; revised 30 July 2003; accepted 6 August 2003.     

Trail following and stowaway behaviour of the myrmecophilous staphylinid beetle,Homoeusa acuminata,during foraging trips of its hostLasius fuliginosus (Hymenoptera: Formicidae)

Summary The behaviour of adultHomoeusa acuminata on trails of its hostLasius fuliginosus was investigated both in the field and in the laboratory. The beetles were active from May to September, accurately following the foraging trails of their hosts up to 20 metres from the nest. Most of the time, they were ignored by the ants, but if attacked they raised their abdomen as a possible appeasement or defensive behaviour. On trails the beetles most probably act as food robbers, feeding on prey collected by ants. The following method, called stowaway behaviour, was used by the beetles: when a beetle encountered an ant carrying a prey back to the nest it jumped on the prey, probably feeding on it while being transported.Laboratory experiments on circular artificial trails demonstrated thatH. acuminata follows a water extract of hindguts of the ants, the source of the trail pheromone. Both beetles and ants responded to an artificial trail of 0.03 hindgut equivalent per cm, but the mean distance followed by the beetles was about twelve times higher than that covered by the ants themselves. In contrast, experiments with solutions of the six fatty acids reported as the active components of the trail pheromone showed that the beetles did not respond at all, and that the ants only respond to the fatty acids at a very high concentration.