Behavioral adaptations for raiding in the slave-making ant,Polyergus breviceps

We studied recruitment behavior of the slavemaking ant Polyergus breviceps,which typically raids colonies of Formica gnava.The first test series demonstrated the importance of social context, by showing that recruitment was high during raiding, but virtually absent during preraid circling and during the return trip after a slave raid. The second test series showed that Formicapupae (alone or together with adults) must be present for workers of Polyegrusto recruit nestmates. The third test series demonstrated that panic alarm by raided Formicais caused by a pheromone, and we suggest that adults of Formicamay be the source of this secretion. Finally, the fourth test series showed that formic acid is lethal to adults of Formicabut has almost no adverse effect on Polyergus.This relative immunity by Polyergusmay enable them to remain organized while entering nests of Formicaduring slave raids.     

Cuticular spectra in the slave-making ant Polyergus rufescens and the slave species Formica rufibarbis

Abstract. The relative proportions of cuticular components having the same retention times were compared between the slave-making ant Polyergus rufescens and the slave ant Formica rufibarbis living in monospecific or mixed colonies. The two species were found to present different spectra. The Formica workers, when enslaved by Polyergus , tend to lose their colony characteristics but they do not seem to adopt the characteristics of Polyergus.     

Phylogeny and phylogeography of the Mediterranean species of the parasitic ant genus <Emphasis Type="Italic">Chalepoxenus</Emphasis> and its <Emphasis Type="Italic">Temnothorax</Emphasis> hosts

We analysed the phylogenetic and phylogeographic relationships of four Mediterranean species of the rare slave-making ant genus Chalepoxenus and eleven of its about 20 Temnothorax host species by sequencing the mitochondrial Cytochrome Oxidase I and II genes. Neighbour-Joining, Maximum Parsimony and Bayesian analyses based on 1320 bp indicate that the genus Chalepoxenus constitutes a monophylum. In all three analyses, C. kutteri from Southwest Europe and the workerless, “degenerate slavemaker” C. brunneus from North Africa form a monophyletic group. C. muellerianus and C. tauricus, distributed in Southern Europe and Ukraine, respectively, form a monophylum in the Neighbour-Joining and the Maximum Parsimony analysis. In our limited set of only 11 of several hundred Temnothorax species, T. flavicornis forms the sister group of Chalepoxenus. Our study further indicates paraphyly of the genus Temnothorax with respect to Chalepoxenus. Moreover, the results suggest that speciation in this slave-making genus is possibly caused by the formation of host races as different Chalepoxenus species use different hosts, and some samples seem to cluster by host species rather than by geographical distance. Received 5 September 2006; revised 17 March 2007; accepted 23 March 2007.     

Cuticular spectra and inter-individual recognition in the slave-making ant Polyergus rufescens and the slave species Formica rufibarbis

Abstract. The relationship between behavioural tests and relative proportions of cuticular components were studied in the slave-making species Polyergus rufescens and the slave and Formica rufibarbis living in either monospecific or mixed colonies. A correlation between the relative proportions of the cuticular products and interindividual recognition exists in each of the two species Polyergus and Formica: Polyergus are fiercely aggressive towards individuals which have different cuticular spectra and originate from a geographically isolated nest. This seems to be true also in the case of Formica living in monospecific colonies. A similar correlation also exists between the two species, which have different cuticular spectra: encounters arranged between them show that free-living Formica are always fiercely aggressive towards Polyergus. The reason why no such correlation seems to exist, however, between Polyergus and Formica when the latter are enslaved and the two species coexist peacefully at the same nest is discussed.     

Incipient sexual isolation in the nasuta-albomicans complex of Drosophila: mating preference in male-, female- and multiple-choice mating experiments

Interracial divergence is an important facet of speciation. Thenasuta-albomicans complex ofDrosophila with sixteen morphologically identical, karyotypically different but cross-fertile races is an excellent system to study a few dimensions of raciation.Drosophila nasuta nasuta, Drosophila nasuta albomicans, Cytorace 1, Cytorace 2, Cytorace 3 and Cytorace 4 of this subgroup have been subjected to male-, female- and multiple-choice mating experiments. Out of 8456 crosses conducted, 7185 had successful matings. The overall impression is that mating is far from random amongst these six closely related races of thenasuta-albomicans complex. The males ofD. n. albomicans, Cytorace 1 and Cytorace 4 in male-choice, the females of Cytorace 1 and Cytorace 2 in female-choice, and the males and females ofD. n. nasuta, D. n. albomicans, Cytorace 1 and Cytorace 4 against the males and females of Cytorace 2 in multiple-choice experiments, had significantly more homogamic matings than expected. Thus in this study of evolutionary experimentation on raciation under laboratory conditions, we have documented the initiation of preference for con-specific matings among closely related and independently evolving members of thenasuta-albomicans complex ofDrosophila.     

Nesting biology of the arboreal fungus-growing ant <Emphasis Type="Italic">Cyphomyrmex cornutus</Emphasis> and behavioral interactions with the social-parasitic ant <Emphasis Type="Italic">Megalomyrmex mondabora</Emphasis>

We describe the extraordinary nesting habits of the fungus-growing ant Cyphomyrmex cornutus (Formicidae, Myrmicinae, Attini) and the natural history of Megalomyrmex mondabora (Formicidae, Myrmicinae, Solenopsidini), a social parasite that inhabits nests of C. cornutus and other small attine ants. The study was carried out at two sites on the Atlantic slope of Costa Rica. The C. cornutus nest is an oblong mass of accreted soil, attached to or suspended from low vegetation in wet forest understory. Less than a fourth of the nest volume has chambers and is inhabited by C. cornutus; the remainder is a semi-solid mass of accreted soil often housing a variety of arthropods, including other unspecialized commensal ant species. Five C. cornutus colonies examined were parasitized by M. mondabora. Colonies of M. mondabora inhabited chambers very near those of the host. In laboratory observations, M. mondabora and C. cornutus workers interacted with little aggression despite the consumption of C. cornutus larvae and fungi by M. mondabora. During most interactions, C. cornutus workers responded submissively, whereas M. mondabora appeared indifferent or nonresponsive. Megalomyrmex mondabora parasitizes several other attine species (Cyphomyrmex costatus, Cyphomyrmex salvini, and Apterostigma goniodes), and it appears therefore a relatively unspecialized social parasite with broad attine hostassociation. The size of M. mondabora workers vary with host species, suggesting M. mondabora sensu lato comprises either cryptic species or the host environment affects worker size. Received 14 September 2006; revised 1 February 2007; accepted 6 February 2007.     

Workers and queens of the European hornetVespa crabro L. have colony-specific cuticular hydrocarbon profiles (Hymenoptera: Vespidae)

Summary Cuticular hydrocarbons were extracted from sixty individual workers from six colonies ofVespa crabro L. and analyzed by combined gas-chromatography/mass spectrometry. Discriminant analysis of the cuticular hydrocarbon profiles of workers and queens showed that the wasps could be grouped by colony and by caste. Stepwise discriminant analysis selected the components which were weighted most heavily in these analyses. Different combinations of cuticular hydrocarbons were important in grouping workers by colony, queens and workers by colony, and workers and queens by caste.     

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.     

Effects of mating rate and delayed mating on the fecundity of Adoxophyes orana

Females of Adoxophyes orana F. v. R. (Lepidoptera: Tortricidae) could mate after one day, or after up to 7 days, after eclosion. It was recorded how many eggs per female were laid, had been fertilized and ultimately hatched. Mating rate was assessed by counting the spermatophores in a female.Egg production did not depend on mating rate, but proportion fertilization of eggs from females with three or more spermatophores was reduced. Delayed mating promoted longevity and changed the pattern of oviposition in time. No correlation was found between the proportion hatching of fertilized eggs and any of the other variables in the experiments.The data were introduced into a population model to compute the relation between fecundity and probability to mate.

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Effets du nombre d'accouplements et du retard de la date du premier accouplement sur la fécondité de Adoxophyes orana

Résumé Des femelles de A. orana F. v. R. (Lep., Tortricid.) ont eu la possibilité de s'accoupler le lendemain de leur émergence. Nous avons dénombré l'effectif d'oeufs pondus par chaque femelle, et calculé leur taux de fertilisation et d'éclosion. Les femelles ont été disséquées et les spermatophores comptés pour déterminer le nombre de copulations. La même procédure a été suivie avec d'autres femelles qui ont pu copuler librement jusquà leur mort, (leur longévité a été notée), mais avec une date du premier accouplement pouvant être retardée jusqu'à 6 jours après l'émergence.La production d'oeufs ne dépend pas du nombre de copulations, mais le taux de fertilisation des femelles avec 3 ou 4 spermatophores a été plus faible. Le retard de la date du premier accouplement augmente la longévité, mais réduit légérement le taux de fertilisation. La production d'oeufs était à peu près proportionnelle à la durée de la vie décomptée à partir du moment où la copulation était possible. Aucune corrélation n'a été mise en évidence entre la taux d'éclosion des oeufs fertilisés et les variables de l'habitat.Pour évaluer ces résultats et obtenir plus de connaissances sur les conséquences des copulations retardées, par exemple provenant de procédures d'interruption des copulations, les données ont été introduites successivement dans un modèle de populations pour établir la relations entre fécondité et probabilité d'accouplement.

     

The effect of B chromosomes on mating success of the grasshopper Eyprepocnemis plorans

The mating ability of E. plorans was tested in laboratory conditions in six experimental units composed of ten males and fifteen females during 31 days. When significant differences were found (three from the six cages, and in totals) they involved a decrease of matings involving males with B chromosomes. The same tendency seems to exist in females, but to a lesser extent, so that a significant effect is only detected when the totals are considered. Accessory chromosomes also delay, in both sexes, the occurrence of the first mating. No mating preferences depending on the number of Bs were detected.     

Multiple mating and sperm displacement in a natural population of Drosophila melanogaster

Summary Mother-offspring data for alcohol dehydrogenase genotypes of a vineyard cellar population of D. melanogaster are best explained by a model that allows 21% of females in the population to mate twice with an 83% level of sperm displacement. A population model with multiple mating and sperm displacement is examined theoretically. A formula for the effective population size is derived under this model. Multiple mating increases the effective population size relative to single mating.     

Cuticular Extracts of Five Common Mantids (Mantodea: Mantidae) of the Eastern United States

We undertook a preliminary investigation of the cuticular extracts of five common mantid species in the eastern United States: Tenodera sinensis (Saussure), T. angustipennis (Saussure) and Mantis religiosa (Linnaeus) introduced from the Old World and Stagmomantis carolina (Johannson) and Bruneria borealis (Scudder), which are New World species. The major components of these mixtures were normal alkanes, predominately hentriacontane, or in the case of the parthenogenic species B. borealis, tritriacontane. Tricontanal was detected in the extracts of all five species, and smaller amounts of other aldehydes and n-tricontanol were detected in some species. Complex mixtures of methyl and dimethylalkanes also were present in these extracts. The composition of the cuticular hydrocarbons of these mantids may be an adaptation for reduction of evaporative water loss in these insects that inhabit open fields.     

No reversion to single mating in a socially parasitic ant

Social Hymenoptera are ideal biological models for the study of the selective forces affecting the evolution of multiple mating (polyandry), because sister species can evolve different lifestyles and mating strategies. Single mating is predicted in workerless social parasites, because the key benefit of multiple mating in social insects, that is, the increase in genetic diversity among worker offspring, does not hold for workerless species. We compared the queen mating frequency between the ant Plagiolepis pygmaea and its derived social parasite P. xene. Previous studies showed that queens of the host P. pygmaea are obligately polyandrous. Here, pedigree analyses of mother–offspring combinations indicate that queens of the parasite P. xene did not revert to single mating; more than 50% of queens mated multiply, with 2–4 males. This result shows that reversal from multiple to single mating may be not selected in polyandrous social insect workerless parasites. We propose that such reversion does not occur when multiple mating is virtually cost free.     

Temporal dynamics of mating and predation in mosquito swarms

We determined the numbers of copulations and predatory attacks in swarms ofAnopheles freeborni (Diptera: Culicidae), and the distribution of these events throughout the duration of the swarming period each day. On 19 evenings of observation, we recorded 2724 copulating pairs leaving swarms and 1351 dragonfly (Pantala hymenaea andErythemis collocata) attacks. Mating activity partially coincided with predator activity. Most copulations occurred between 10 and 20 min after the swarms formed, while predation events were most frequent during the initial 15 min of the swarm. We calculated the ratio of copulations to predatory attacks during the swarming period. This ratio was significantly higher in an area sheltered by trees than it was in the open. We suggest that physiological and ecological constraints other than predation operate on the mating system of this anopheline to affect the timing of swarm initiation and swarm site selection.     

Host nest preference and nest choice in the cuckoo paper wasppolistes sulcifer (Hymenoptera: Vespidae)

Polistes sulcifer is a cuckoo paper wasps, an obligate social parasite which must usurp a colony of another species in order to reproduce. Field data show thatP. sulcifer females usurp exclusively nests belonging to one species only (P. dominulus). Moreover, they are more frequently found on large and puparich nests. A series of laboratory trials, in which parasite females were offered a binary choice of nests with different characteristics, confirm both the species specificity betweenP. sulcifer andP. dominulus and the parasite's preference to usurp larger nests containing pupae. The data support the hypothesis thatP. sulcifer females choose between available nests. The biological meaning of these findings is discussed.     

Cuticular Hydrocarbons of Reticulitermes (Isoptera: Rhinotermitidae) from Northern California Indicate Undescribed Species

Cuticular hydrocarbon mixtures of Reticulitermes samples from disparate locations in northern California were characterized and correlated with species determinations. Literature records indicate that there are two extant species of Reticulitermes in northern California: Reticulitermes hesperus Banks and R. tibialis Banks. We identified five distinct hydrocarbon phenotypes in Reticulitermes from northern California. Termites were diagnosed morphologically as R. tibialis for all five cuticular hydrocarbon phenotypes based on available keys to soldiers. Commonly accepted distributions of Reticulitermes in northern California indicate that our primary collection sites should only produce R. hesperus. On the basis of cuticular hydrocarbons alone we suggest that there are two or more undescribed taxa of Reticulitermes in northern California, or that described species of Reticulitermes occur in northern California, but have never been noticed before. Therefore, we conclude that the taxonomy of Reticulitermes in North America is in need of revision.