Raiding behavior of the dulotic antChalepoxenus muellerianus (Finzi) in the field (Hymenoptera: Formicidae,Myrmicinae)

Summary Little information is available regarding the raiding behavior in nature of dulotic ants belonging to the tribeLeptothoracini. Between July 17 and 24, 1991, several raids ofChalepoxenus muellerianus (Finzi) were observed in nature near Tignale/Lago di Garda, Italy. Apparently, this species raids frequently during its summer raiding season (5 raids were observed during 7 days spent observing 8 colonies). A singleChalepoxenus colony sometimes raids more than one host colony more or less simultaneously. Observations during which oneChalepoxenus colony raided another and captured slavemaker brood indicate that intraspecific raids can occur either accidentally, or as a result of competition or territoriality when there is a sufficient dense slavemaker population.     

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.     

Life Cycle of the Tick Haemaphysalis Leporis-palustris (Acari: Ixodidae) Under Laboratory Conditions

The life cycles of two separate populations (colonies A and B) of the rabbit tick, Haemaphysalis leporis-palustris, were studied under laboratory conditions. Domestic New Zealand rabbits, Oryctolagus cuniculus, and wild rabbits, Sylvilagus brasiliensis, were used as hosts for ticks from colony B and only O. cuniculus rabbits were used as hosts for ticks from colony A. Developmental periods were observed in an incubator at 27±1°C and RH 90±5%. Larvae from colonies A and B fed for 8.0±3.7 days and 8.5±1.3 days, respectively, on O. cuniculus. On S. brasiliensis larvae from colony B fed for 7.2±1.3 days. Nymphs from colony A fed for 8.1±1.4 days on O. cuniculus and nymphs from colony B fed for 8.1±1.0 days on S. brasiliensis. Only one engorged nymph from colony B was recovered from O. cuniculus. Females from colony A fed for 20.9±5.9 days on O. cuniculus and females from colony B fed for 18.6±2.4 days on O. cuniculus and 18.7±3.7 days on S. brasiliensis. Engorged larvae from colony A required 13.7±3.7 days to molt while engorged larvae from colony B required 11.8±3.0 and 11.5±1.8 days to molt, after having fed on O. cuniculus and S. brasiliensis, respectively. Engorged nymphs from colonies A and B required 16.3±1.9 days and 14.7±1.4 days to molt, respectively. Engorged females from colonies A and B required 4–7 and 3–5 days, respectively, to start oviposition. Mean egg incubation periods lasted for 33–34 days. For ticks from colony B, host species accounted for significant differences (p<0.05) in larval and nymphal feeding periods, oviposition weights and CEIs. Significant differences (p<0.05) between the two colonies when ticks fed on O. cuniculus were observed for larval and nymphal feeding and premolt periods, engorged female and oviposition weights and conversion efficiency indexes (CEI). S. brasiliensis were always a more suitable host for H. leporis-palustris than O. cuniculus. Significantly more larvae and nymphs engorged and molted when fed on S. brasiliensis (p<0.001). Females fed S. brasiliensis were more successful to lay fertile eggs and showed the highest engorged and egg mass weights, and the highest CEIs. Data of H. leporis-palustris fed on wild rabbits (one of its natural host species) are reported for the first time.     

Cuticular hydrocarbons in workers of the slave-making ant Polyergus samurai and its slave, Formica japonica (Hymenoptera: Formicidae)

Comparisons of cuticular hydrocarbons between workers of the dulotic ant Polyergus samurai and its slave, Formica japonica, were carried out. Gas chromatography–mass spectrometry showed that the slave‐maker and its slave shared the major cuticular hydrocarbon compounds, but possessed several minor products unique to each species. No difference in hydrocarbon composition was detected between enslaved and free‐living F. japonica workers, suggesting that association with P. samurai has no qualitative effect on hydrocarbon composition in these ants. Principal component analyses of the cuticular hydrocarbon profiles (CHP) revealed that (i) CHP was species specific in a given mixed colony; and (ii) among mixed colonies, P. samurai workers had species‐colony specific CHP, while the same feature was not always found in enslaved and free‐living F. japonica workers. Therefore, a ‘uniform colony odor’ in terms of CHP is not achieved in naturally mixed colonies of P. samurai nor those of its slaves, F. japonica.     

Genetic differentiation amongst populations of the coral Pocillopora damicornis off southwestern Australia

An electrophoretic study of genetic differentiation amongst local populations of the reef-coral Pocillopora damicornis was used to group coral heads into units defined as the area of effective dispersal of a clone, and termed colonies. For reefs off southwestern Australia, colonies were usually under a few hundred metres in extent. Although most new recruits within a colony were derived asexually, sexually produced propagules acted to connect populations outside the boundaries of a colony. Such connections were weak, and allelic frequencies varied considerably over a few kilometres. The primary agent of genetic differentiation was suggested to be the small effective population size resulting from the asexual proliferation of a few genotypes at any site. The effective number of genotypes per colony was approximately six. Asexual reproduction appears also to limit gene flow and accentuate selection in this species.     

Division of labour between foraging workers of the ponerine antPachycondyla caffraria (Smith) (Hymenoptera: Formicidae)

Summary Two categories of foraging worker were found inPachycondyla caffraria from Senegal. One specialises in hunting and the other in collecting sweet liquid food. In the category of hunters there are two sub-categories: stingers and transporters. When the workers were offered a group of live termites (20–30Microcerotermes sp.), two types of behaviour were observed: some workers stung and paralysed the prey, while others transported the termites back to the nest. While on a foraging raid, the two roles are undertaken by two distinct groups of workers, and the roles are not interchanged during the course of the raid. The number of hunters, liquid collectors and transporters of prey are highly correlated with colony size.     

Colony structure of a bamboo-dwellingTetraponera sp. (Hymenoptera: Formicidae: Pseudomyrmecinae) from Malaysia

Summary The colony structure of the bamboo-inhabiting SE-Asian pseudomyrmecine antTetraponera sp. PSW-80 nearattenuata F. Smith was investigated at the Ulu Gombak Field Studies Centre, Selangor, West-Malaysia. Based on the dissection of 54 stem internodes from 12 different culms of the large bambooGigantochloa scortechinii Gamble and on the mapping of three colonies, the following demographic characteristics emerge. The colonies are monogynous but highly polydomous (at least up to 36 internodes and up to 9 stems occupied) and very populous for a pseudomyrmecine not involved in an ant-plant mutualism. One completely censused colony had 6953 adult workers and 2079 alates (adults plus pupae). The single queen suppresses gyne development in her own nest and, to a lesser extent, in other nests within the same stem. The overall numerical sex ratio was 0.961 (females:males), the investment sex ratio, 2.931, i.e., almost exactly the 31 ratio expected for a monogynous outbred hymenopteran in which the colony queen also produces all the male offspring. Brood is distributed to all other nest chambers from the queenright chamber. The symbiotic pseudococcids (Kermicus wroughtoni Newstead) are present in all inhabited internodes, with small early instar individuals prevailing numerically by far over the larger stages. The rieht well secluded honeydew supply within the internode and the efficient architectural protection provided by the internode wall (access usually only through a 2 × 3 mm-hole) allowT. sp. PSW-80 to reach an unusually large colony size without being an aggressive and protective plant mutualist like other members of its subfamily with similar demographic features.     

Raiding and Foraging Behavior of the Blood-Red Ant,Formica sanguinea Latr. (Hymenoptera,Formicidae)

In this paper we report the results of a detailed study on the behavioral ecology of slave raiding and foraging activity in the European blood-red ant, Formica sanguinea Latr. The field study was conducted over an unbroken period of 78 days, during which the activity of two dulotic colonies of this facultative slave-maker was observed for 10 h each day. It was possible to observe 26 raids distributed over 23 days, among which 18 were followed by the sacking of nests belonging to the species F. cunicularia, F. fusca, and Lasius emarginatus, whereas 8 failed. Simple, continuous, and simultaneous raids occurred. We recorded the timing, frequency, distance, and direction of slave raids, including the number of participants and the type of booty. Particular attention was devoted to the scouting behavior and raiding organization. Moreover, every day, we observed foraging and predatory behavior, during which adult insects (mainly ants), seeds, and berries were retrieved to the dulotic colonies. On the basis of our observations F. sanguinea seems to be a very efficient slave-maker and predatory species of the Raptiformica subgenus. Moreover, its dulotic behavior may be regarded as a continuation and an expansion of its foraging and predatory behavior, as predicted by Darwin's hypothesis for the origin and evolution of slavery in ants.     

Optimal and central-place foraging theory applied to a desert harvester ant,Pogonomyrmex californicus

Summary Certain predictions of optimal- and central place-foraging theory were tested on the desert harvester ant, Pogonomyrmex californicus. Colonies were offered three different sizes of oat seed and found to maximize net energy intake (ei) over time (t _i ) by harvesting the seed sizes with the highest e _i /t _i rank. Two aspects of t _i were measured that were assumed constant in previous studies. The handling components of t _i (time required to manipulate the seed and travel time back to the colony with the food) were measured and found to be positively correlated with seed size. The manipulation success rate (the percentage of handled seeds successfully picked up) decreased with increased seed size. These results point out how important it is to measure all parameters of e _i /t _i rather than to assume constancy with both prey type and foraging distance. The relative abundance of less preferred food types was important in determining the proportion of preferred types in the diet. The food supply of eight colonies was manipulated experimentally over a 25-day period. Four deprived colonies were constrained within aluminum enclosures to prevented foraging. The remaining four satiated colonies were given food ad libitum. The niche breadths of the treated colonies were then compared to controls, but found not to differ significantly. Seed baits were offered at three distances from the colony to test whether selectivity increased with disance. Contrary to theoretical predictions, all colonies harcested about the same proportion of each seed size at each distance.     

Colony cycle of an Australian swarm-founding paper wasp,Ropalidia romandi (Hymenoptera: Vespidae)

Summary Colonies of an Australian swarm founding polistine wasp,Ropalidia romandi, on the Atherton Tableland, Queensland, manage perennial nests by practicing seasonal colony activity. In summer nests, most cells were occupied by immatures of all developmental stages. The proportion of cells that did not contain immatures increased towards winter, when most nest cells did not contain immatures and half of these winter nests had rather large amounts of nectar deposited in empty cells. While the visits to tree flowers byR. romandi were not frequent in summer, nearly 60 % of insects collected on tree flowers in winter wereR. romandi. With such seasonal switching in the modes of colony reproductive activity and of nectar foraging behavior,R. romandi responds to its physical and biotic environment. In this way,R. romandi may be able to continue colonies throughout the year, with much reduced level of colony activity in winter, in areas with seasons that are unfavorable for reproductive activity of a colony.     

Threat,Signal or Waste? Meaning of Corpses in two Dulotic Ant Species

Ant corpses, besides representing threat of infection by pathogens and parasites, can also be used during interspecific conflicts to inhibit the activity of the attacked colony, or they can be consumed as food. In the view of the former, the signal properties of corpses can be manifold. Besides discriminating nestmates and foes, the corpses of different ant species may act as cues for foragers, signaling the presence of other rival species, and triggering appropriate responses (e.g., alarm, retreat or foraging). In our study, we examined the responses of the facultative slave-maker Formica sanguinea and those of the obligate Polyergus rufescens towards corpses of nestmates, non-nestmate conspecifics, heterospecific slave-makers and their slaves, and corpses of non-enslaved host species under laboratory conditions. Both dulotic species responded differently to corpses of different origin. In F. sanguinea, the most intensive response was elicited by the corpses of P. rufescens and its slave, but also the corpses of non-nestmate conspecifics and their slaves elicited many adverse responses. In P. rufescens, the corpses of non-nestmate conspecifics and their slaves elicited the most adverse response. Both dulotic species distinguished corpses of their slaves from corpses of non-enslaved hosts. Based on our results, ant corpses are not meaningless objects scattered in the field, but cues carrying information that trigger different behavioral responses, and in F. sanguinea they can even represent an important food source.     

Raiding Activity of an Obligate (Polyergus breviceps) and Two Facultative (Formica puberula and F. gynocrates) Slave-Making Ants

Slave-making ants are social parasites that exploit the labor of workers from their host species by keeping them captive in the slave-maker nest. Slave-makers vary in their degree of specialization, ranging from obligate slave-makers that cannot survive without captives, to facultative slave-makers, which are often found living independently. Our study system included one obligate slave-maker, Polyergus breviceps, two facultative slave-makers, Formica puberula and F. gynocrates, and two hosts, F. occulta and F. sp. cf. argentea. We observed all raids conducted during two raiding seasons by seven P. breviceps colonies, two F. puberula colonies, and two F. gynocrates colonies. We report on raiding frequency, average raid distances, and then compare the probability of being raided multiple times in a single raiding season for the two host species. We also report on the spatial distribution of slave raids, which suggests that slave-makers avoid raiding in areas used by other slave-maker colonies. This is the first report of raiding activity for P. breviceps in this location, and the first report of raiding activity of any kind for F. puberula and F. gynocrates.     

Are tsetse fly populations close to equilibrium?

Glossina or tsetse flies, the vectors of sleeping sickness, form a unique group of insects with remarkable characteristics. They are viviparous with a slow rhythm of reproduction (one larva approximately every 10 days) determined by the regular ovulation of alternate ovaries. This unusual physiology enables the age of the females to be estimated by examining the ovaries.The resulting ovarian age structure of tsetse fly populations has been used to develop research into the demography of tsetse flies. Several authors have proposed methods of estimating population growth rates from ovarian age distribution data. However, such methods are applicable only when the growth rate () is equal to 1 (i.e. the intrinsic rate of increase r is equal to 0). In fact, in this type of estimation, the adult survival rate a (or equivalently the mortality rate) cannot be dissociated from the growth rate.Other independently determined demographic parameters must be used to remove this lack of identiflability. We have built a matrix model of the dynamics of tsetse fly populations which enables the growth rate to be calculated from the pupal survival rate, the pupal period and the adult survival rate. Assuming that the age-groups of the population studied have reached a stable distribution, it is possible to calculate the probabilities for the observed sample of belonging to each of the age-groups, to construct a likelihood function and thus to obtain an estimate of the apparent survival rate = a/ If the pupal survival rate and the pupal period are known, a and can then be calculated from .The application of this method to data collected for over two annual cycles in a savannah habitat (Burkina-Faso) showed a high overall stability in the populations of Glossina palpalis gambiensis. Seasonal fluctuations could be easily interpreted as being the result of climatic changes between the dry and rainy seasons.     

A “protective shell” around the larval cocoon of <Emphasis Type="Italic">Cephalodiscus densus</Emphasis> Andersson, 1907 (Graptolithoidea,Hemichordata)

Within the framework of the Italian XVII PNRA expedition (austral summer 2001–2002), several colonies of the Graptolithoidea (=Pterobranchia+Graptolithina) species, Cephalodiscus densus Andersson and C. hodgsoni Ridewood, were collected by trawl from Tethys Bay (Terra Nova Bay, Ross Sea). These organisms were maintained in aquaria for 2 weeks and their behaviour observed. The dissection of some colonies of C. densus allowed the reconstruction of the eggs fate and the documentation of the formation of a protective shell around the cocoons of larvae settled within the parental colony encasement. The shell is produced by cementing size-selected debris, either of organic or inorganic origin, accumulated inside the encasement. This is the first documentation of such a structure within living Hemichordata and it helps to reinterpret some of the resting structures within zooidal tubes or thecae of particularly well-preserved fossil graptolites.     

Structural specificity of sugars that inhibit gliding motility of Cytophaga johnsonae

It is a common observation that gliding bacteria form raised, smooth-edged colonies on nutrient-rich media, and typical thin, spreading, uneven-edged colonies on nutrient-poor media. An earlier study of the effect of different sugars on colony spreading by Cytophaga johnsonae was expanded to include the effects of several sugars and other organic compounds on the motility of groups of cells (rafts), and latex bead movement on cells' surfaces. When the structures of those sugars that did, or did not, affect raft formation and colony spreading were compared, it was noted that those sugars that inhibited these two manifestations of gliding motility all possessed a common sub-structure, that found in the portion of glucopyranose comprising carbons 3, 4, 5, and 6. If these structural features were altered chemically or stereochemically, the resulting molecule had little to no effect on motility. The differential effects of some compounds on raft formation, colony spreading, and bead movement are noted. A regulatory mechanism that would turn off motility in the presence of an inhibitory sugar is implicated, and the relevance of such a system to the life of the organism is discussed. We report, as well, additional compounds that will serve as carbon and energy sources for C. johnsonae.     

Chorion genecis-regulatory DNA restricts tissue specificity of reporter gene expression in transformedDrosophila

P element mediated germ-line transformation was used to study the developmental specificity ofDrosophila chorion gene regulatory sequences directing expression of the bacterial reporter genes for chloramphenicol acetyltransferase (CAT) and -galactosidase (lacZ). DNA fragments containing 5 flanking plus the entire 5 untranslated and the beginning of the coding region of either thes36 or thes15 chorion gene are able to confer on the reporter genes normal tissue as well as temporal specificity of expression, exclusively in the ovary of transformed female flies. However, if 5 untranslated and coding regions are omitted, normal ovarian expression is maintained but tissue specificity is relaxed: expression of the reporter gene is detected both in the ovary and in specific non-ovarian tissues of transformed females and males. The evidence suggests that the missing 5 untranslated and coding sequences may include negative elements that normally suppress expression in non-ovarian tissues, and that these putative elements are distinct from those that prevent premature expression in the ovarian follicles. The exact location of ectopiclacZ expression within the internal male genitalia depends on the constellation of 5 flanking chorion regulatory sequences included in theP element constructs. Ectopic expression of theCAT gene in the male genitalia unders15 promoter control can be abolished by mutating the hexamer TCACGT, a sequence previously shown to be essential for the normal expression of this chorion gene in the ovary.by A. Spradling     

Do host species evolve a specific response to slave-making ants?

Background

Social parasitism is an important selective pressure for social insect species. It is particularly the case for the hosts of dulotic (so called slave-making) ants, which pillage the brood of host colonies to increase the worker force of their own colony. Such raids can have an important impact on the fitness of the host nest. An arms race which can lead to geographic variation in host defenses is thus expected between hosts and parasites. In this study we tested whether the presence of a social parasite (the dulotic ant Myrmoxenus ravouxi) within an ant community correlated with a specific behavioral defense strategy of local host or non-host populations of Temnothorax ants. Social recognition often leads to more or less pronounced agonistic interactions between non-nestmates ants. Here, we monitored agonistic behaviors to assess whether ants discriminate social parasites from other ants. It is now well-known that ants essentially rely on cuticular hydrocarbons to discriminate nestmates from aliens. If host species have evolved a specific recognition mechanism for their parasite, we hypothesize that the differences in behavioral responses would not be fully explained simply by quantitative dissimilarity in cuticular hydrocarbon profiles, but should also involve a qualitative response due to the detection of particular compounds. We scaled the behavioral results according to the quantitative chemical distance between host and parasite colonies to test this hypothesis.

Results

Cuticular hydrocarbon profiles were distinct between species, but host species did not show a clearly higher aggression rate towards the parasite than toward non-parasite intruders, unless the degree of response was scaled by the chemical distance between intruders and recipient colonies. By doing so, we show that workers of the host and of a non-host species in the parasitized site displayed more agonistic behaviors (bites and ejections) towards parasite than toward non-parasite intruders.

Conclusions

We used two different analyses of our behavioral data (standardized with the chemical distance between colonies or not) to test our hypothesis. Standardized data show behavioral differences which could indicate qualitative and specific parasite recognition. We finally stress the importance of considering the whole set of potentially interacting species to understand the coevolution between social parasites and their hosts.

     

Synergism of synthetic acyltripeptide and its analogs with recombinant interferon γ for activation of antitumor properties of human blood monocytes

Summary Human blood monocytes freshly isolated by centrifugal elutriation from healthy volunteers were not cytotoxic to allogeneic A375 melanoma cells, but they were activated to the tumoricidal state by incubation in vitro with FK-565, (heptanoyl--D-Glu-(L)-meso-,-A₂pm(L)-D-AlaOH), which is a synthetic acyltripeptide closely resembling cell wall peptidoglycan peptides of Streptomyces in structure. Among 11 different derivatives of FK-565, 7 analogs were more potent activators of monocytes for tumor cell killing than FK-565. The maximal expression of tumoricidal nonocytes was dependent on the concentration of FK-565 or its analogs added and the ratio of monocytes to target tumor cells. In a parallel experiment, a combination of a subthreshold concentration of FK-565 or its analogs (FR-42148 and FR-42149) and recombinant interferon (rIFN-) induced significant monocyte-mediated tumorcell killing, indicating that the effects of rIFN- and acyltripeptide or its analogs in monocyte activation are synergistic. In contrast to rIFN-, recombinant rIFN-A and rIFN- had additive effects with acyltripeptide or its analogs in human monocyte activation. These results suggested that synthetic acyltripeptide and its analogs combined with rIFN- could be of clinical value for in situ activation of the tumoricidal activity of human blood monocytes responsible for eradication of cancer metastases.     

Nest characteristics and recruitment behavior of absconding colonies of the African honey bee,Apis mellifera scutellata,in Africa

Absconding behavior was investigated in a naturally occurring population of honey bees in the Okavango River Delta, Botswana. Fifty percent of all colonies excavated in the field between October and December had abandoned the nest or were preparing for absconding, suggesting that an absconding season began in the Delta in October or November. However, the factors influencing absconding during this period were unclear, and there were no distinct differences in nest characteristics of the absconding and nonabsconding colonies. Waggle dance activity in observation colonies preparing for absconding was not used to preselect a specific nest site prior to departure. However, in two of the three colonies examined recruitment activity indicated the general direction of colony travel. The distances indicated by these dancers ranged between 6 and 16 km. Since these distances were three to four times greater than those communicated by dancers in nonabsconding colonies, workers from absconding colonies may sample potential forage or nest sites well outside their regular foraging range.     

A size-distance relation in Homoptera-tending thatch ants (Formica obscuripes,Formica planipilis)

Summary In 20 of 22 study colonies, Homoptera-tending workers of the thatch antsFormica obscuripes andF. planipilis exhibited a significant size-distance relation, with smallest tenders working closest to the primary nest. No such relation was observed in scavengers working over the same range of distances in any of the 22 colonies. This paper describes the size-distance relation in tenders quantitatively, examines its expression given variation in Homoptera distribution, and compares it to similar patterns observed in otherF. rufa-group species. Three hypotheses on the adaptive significance of the size-distance relation are discussed: that the relation increases energetic efficiency, improves colony defense, or decreases the rate of getting lost in smaller tenders.