Christian Peeters

Institute of Ecology and Environmental Sciences IEES-Paris | iEES · Evolutionary Ecology

Many organismal traits vary with body size, often reflecting trade-offs in the face of size-dependent constraints. For example, Haller's rule, the allometric pattern whereby smaller organisms have proportionally larger brains, can have carry-on effects on head design as the brain competes for space with other structures. Ant species with polymorphi...

Rhopalomastix is a bark digger ant that nests in the bark of living trees. The ants share a mutualistic relationship with diaspidids (armoured scale insects), housing them in their nest tunnels in the bark of a tree. Two colonies of Rhopalomastix sp. were sampled from two cultivars of mango trees in a mango plantation in Thailand. The architecture...

Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their abi...

As in other Hymenoptera, adult ants cannot secrete silk, unlike the larvae that spin a cocoon prior to metamorphosis. Fisher and Robertson (1999) first showed the existence of a silk gland in the head of adult Melissotarsus beccarii workers, and we confirm this with detailed histology and ultrastructural comparisons of both queens and workers. This...

Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their abi...

Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their abi...

We review the latest molecular phylogeny of ants (Borowiec et al 2019) that recognizes poneroids not as a collection of primitive or ancestral ants but as an evolutionary radiation that occurred independent from and simultaneous to formicoids (90% of extant ants). We discuss how to assess social complexity in poneroids and formicoids. Poneroid taxa...

All social insects show two alternative founding strategies: independent vs. dependent (= fission). I review two very distinct adaptations that evolved to reduce mortality risks of foundresses : (i) in many species across all lineages, established colonies can split into daughter colonies, so that founding queens are helped by nestmate workers who...

Flightless reproductives (ergatoid queens, short-winged queens, gamergates) are known in at least 75 genera belonging to most subfamilies of ants. The great morphological heterogeneity among flightless reproductives, especially the extent of dimorphism relative to conspecific workers (or the winged queens of related species) results from convergent...

Ant societies consist of reproductive and sterile adults that show tremendous diversity of phenotypes. These include permanently wingless queens and a soldier caste that evolved convergently in many genera. Myrmecologists describe ant castes with terminology based on form, or function, or both, moreover terms are used inconsistently in the literatu...

Rhopalomastix is a myrmicine ant distributed throughout tropical parts of Asia, with almost nothing known about its biology. Its closest relative Melissotarsus in Africa is the only ant genus known to live with diaspidid scale insects inside their nests, and to rely on these for food. Twelve colonies of four species of Rhopalomastix were sampled fr...

English (original) version at doi:10.5281/zenodo.3066005

An introduction to the highly diverse (> 1300 species) ant fauna of Madagascar, resulting from > 80 million years of isolation from continental Africa and Asia. We discuss the natural history and ecology, distribution patterns, and how to identify the different genera. Included are unpublished field observations about several key species. Two of t...

Background While thousands of ant species are arboreal, very few are able to tunnel through living wood. Ants of the genus Melissotarsus (subfamily Myrmicinae) inhabit tunnel systems excavated under the bark of living trees, where they keep large numbers of symbiotic armoured scale insects (family Diaspididae). Chewing through healthy wood requires...

Paraponera clavata is a large, notorious, and widely distributed ant, yet its colony founding behavior is poorly known. In the laboratory, a dealate queen collected from Peru reared a first generation of ten adult workers over 18 months; eight cocoons and several larvae failed. Food was obtained outside the nest and given to larvae. It took five an...

Gesomyrmex (subfamily Formicinae) is a poorly known arboreal ant from the Oriental tropics. We sampled colonies in three localities (NE Thailand, peninsular Malaysia, and Sabah) and examined inhabitants of ten nests inside living branches. None of the nests had a reproductive dealate queen, indicating colonies are polydomous. We distinguished three...

Among thousand species of arboreal ants, relatively few build their nests inside living wood. Melissotarsus is an Afrotropical ant that dig galleries under the bark of living trees, where they keep scale insects as symbionts. Chewing through healthy wood requires tremendous power, intuitively unexpected in 2.5mm-long individuals. Using histology, s...

Supporting Information for Peeters & Aron (2017) Table S1. Field observations of mating, dispersal and founding behaviour in Cataglyphis desert ants. Table S2. Mature colony size and sexual production in different Cataglyphis species. Figure S1. Presence or absence of wing muscles inside Cataglyphis queen thorax. Figure S2. Weak dimorphism in body...

Mutualisms between ants and sap-sucking insects generally involve clear benefits for both partners: the ants provide protection in exchange for honeydew. However, a single ant genus associates with armoured scale insects (Diaspididae) that do not excrete honeydew. We studied three colonies of Melissotarsus emeryi ants from two localities in Mozambi...

Supplemental information

Sexual activity is only a brief moment in the life of ant colonies, but it determines several characteristics of life history. Mating behaviour, distance of female dispersal and mode of colony foundation are interlinked. In species exhibiting ‘male aggregation’ (males and queens fly and mate away from natal nests), newly mated queens have no other...

We observed a large and fairly compact group of Prenolepis subopaca workers walking down a tree at sunset. Many workers had swollen abdomens, consistent with retrieval of honeydew. The group vanished in leaf litter on the ground.

The great evolutionary success of insects is partly linked to the innovation of the cuticle, which underlies a complex exoskeleton with varied functions. Cuticle development is costly since chitin and cuticular proteins require ingested nitrogen. Studying cuticle thickness on a comparative basis allows an insight in the trade-off between offspring...

Habitat heterogeneity has a complex effect on ant species richness and community structure (both alpha- and beta-diversity). Savannahs and forests are thought to have distinct species assemblages, but studies comparing savannah–forest mosaics produced conflicting results, with savannah (the less complex ecosystem) poorer in species, equally rich, o...

Megalomyrmex Forel (Myrmicinae: Solenopsidini) consists of 44 species with diverse life history strategies. Most species are predatory and may also tend honeydew-producing insects. A morphologically derived group of species are social parasites that consume the brood and fungus garden within fungus-growing ant nests. The reproductive strategies of...

Most ponerine ants have flying queens that monopolise sexual reproduction, but in a minority of species, workers can also mate and lay fertilised eggs. Such ‘gamergates’ reproduce in addition to queens in some species but have replaced queens entirely in other species. The occurrence of a functional spermatheca in workers often appears associated w...

Ant colonies are organized similarly to those of wasps and bees: reproductive altruism, age polyethism, and complex communication. Yet ants exhibit more species, much higher total biomass, and their lifestyles and diet are more diverse. Hence, factors additional to sociality must be involved in this evolutionary diversification. We argue that loss...

Various ants can link their bodies in chains or other structures, a striking example of cooperation. Chain behavior in Leptogenys sp. functions for the collective transport of large millipedes. This undescribed Leptogenys species is a swarm raider with a small range of prey: millipedes belonging to four orders (Polydesmida, Spirostreptida, Spirobol...

Different immature stages and adults of the new species Schizaspidia diacammae (Chalcidoidea: Eucharitidae) were found inside cocoons of Diacamma scalpratum (Formicidae: Ponerinae). Wasp larvae were feeding on ant pupae, while other host cocoons yielded five wasp pupae and both male and female adults. Parasitized cocoons are cut in a distinct manne...

Because of problems of rarity, sampling bias, and general lack of informative characters, immature stages of parasitic Hymenoptera are seldom used to resolve phylogenetic relationships. However, the ant-parasitic Eucharitidae are an exception. The adults and immature stages of Schizaspidia diacammae n. sp. (Eucharitidae: Eucharitinae: Eucharitini)...

Ant colonies are organized similarly to those of wasps and bees: reproductive altruism, age polyethism and complex communication. Yet ants exhibit more species, much higher total biomass, and their lifestyles and diet are more diverse. Hence, factors additional to sociality must be involved in this evolutionary diversification. We argue that loss o...

The Malagasy endemic ant Malagidris sofina (Bolton and Fisher 2014) nests on cliff faces in natural rock alcoves or clay banks. Colonies have single ergatoid queens and reproduce by fission. Each nest has a funnel-shaped entrance that projects horizontally from the cliff face. We examine three hypotheses for the function of the funnels— water exclu...

Ergatoid (= permanently wingless) queens do not disperse individually from their natal colonies, instead they walk with nestmate workers to new nesting sites during the fission of existing colonies. Very few observations of dependent colony foundation are available, and it must often be studied with indirect data. Thirty-five colonies of Monomorium...

The concerted evolution of morphological and behavioral specializations has compelling examples in ant castes. Unique to ants is a marked divergence between winged queens and wingless workers, but morphological specializations for behaviors on the ground have been overlooked. We analyzed thorax morphology of queens and workers in species from 21 of...

The mechanisms by which development favors or constrains the evolution of new phenotypes are incompletely understood. Polyphenic species may benefit from developmental plasticity not only regarding ecological advantages, but also potential for evolutionary diversification. For instance, the repeated evolution of novel castes in ants may have been f...

The epiphyte Dischidia major has highly modified leaves (‘pitchers’) that provide lodging for various ants, especially Philidris (Dolichoderinae) but also Cataulacus and Crematogaster (Myrmicinae). In return, the plants can obtain extra nutrients but this depends on intimate contact between the branching adventitious roots growing within inhabited...

The ability to disperse and establish new colonies is crucial to the ecological success of ants. However, founding queens are often alone, which means that they face the same dangers as solitary insects. Colony-founding behaviours have diversified tremendously across the ants, and underlie their capacity to colonize almost all terrestrial habitats....

Si toutes les fourmis partagent la même structure sociale, elles présentent en revanche une grande variété de tailles. Cette diversité peut s'observer parmi les individus d'une seule colonie, favorisant un partage du travail plus efficace, mais aussi entre des espèces possédant un régime alimentaire semblable. Dans ce cas, l'éventail de tailles per...

Nest emigrations are perilous for social insect colonies. Outside their nests, adults and brood are exposed to dangers. The behavioural mechanisms of emigration are thus likely to be under strong selective pressures.Most studies on emigration have focused on monogynous species where survival of the queen is paramount, but emigration processes are l...

Following a comprehensive introduction on ant biology, we describe 45 of the species most commonly found in France (out of a total of more than 200 species). Identification keys are based on characters that can be observed with a hand lens. Many photographs by T. Monnin describe ant behaviours in different environments.

Most ponerine ants have colonies with up to a few hundreds of workers, but there has been sporadic evolution of species with more populous colonies. Forty two nests of Paltothyreus tarsatus were excavated from three distinct habitats in the Ivory Coast. Colonies were monogynous in Comoé (forest and savanna), but polygynous in Taï (rainforest). Mean...

Among social Hymenoptera, only some ant genera have more than one morphological kind of non-reproductive adults. Individuals that are bigger than ordinary workers can function for defence and/or food storage. In Crematogaster (Orthocrema) smithi from Arizona, a third caste exists in addition to winged queens and workers; it is intermediate in size,...

Ants have distinct morphological castes (queens and workers), but aberrant queen-worker “intercastes” occasionally occur, both in wild and laboratory conditions. Intercastes are rare, however, such novel phenotypes may have evolutionary significance. Their morphology is highly variable in any given species, providing valuable information about the...

The spectacular success of eusocial insects can be attributed to their sophisticated cooperation, yet cooperation is conspicuously absent during colony foundation when queens are alone. Selection against this solitary stage has led to a dramatically different strategy in thousands of eusocial insect species in which colonies are started by groups o...

The South American seed-harvester ant Pogonomyrmex laticeps has dimorphic queens: ergatoid (permanently wingless) and brachypterous (short, non-functional wings). Surveys in western Argentina indicated that colonies near Chilecito, La Rioja Province, produced only ergatoid queens, while those near Punta Balasto, Catamarca Province (263 km away), pr...

Many ants have independently evolved castes with novel morphology as well as function, such as soldiers and permanently wingless (ergatoid) queens. We present a conceptual model, based on modularity in morphology and development, in which evolutionary innovation is facilitated by the ancestral ant polyphenism of winged queens and wingless workers....

In queenless species of ants, colonies consist of workers with equivalent reproductive potentials. Aggressive interactions regulate fertility and sexual activity. The genus Diacamma is unusual, because monogyny is regulated by mutilation (i.e., removal of a pair of tiny innervated thoracic appendages) of all young workers. One exception is the ‘nil...

Flight is a one-off event in ants, hence after mating, the wing muscles of winged queens can function as protein reserves during independent colony foundation (ICF). Another strategy occurring in many unrelated lineages is dependent colony foundation (DCF). DCF does not require queens with expensive wing muscles because dispersal is on foot, and a...

In 99% of ant species, workers never mate and only the queens have stored sperm to fertilize their eggs. It is only in a few taxa (about 200 species in Amblyoponinae, Ponerinae and Ectatomminae) that workers can mate and reproduce sexually (‘gamergates’ or ‘G’). In some species (e.g., Dinoponera) gamergates have replaced queens completely, while in...

Winged queens have been replaced by wingless queens in many genera of ants. Since wing muscles are absent, their thorax is simplified and worker-like ("ergatoid"). Ergatoid queens exhibit very diverse characteristics as a result of convergent evolution. Eutetramorium (subfamily Myrmicinae) is a genus endemic to Madagascar with two known species. E....

The ecological success of ants results notably from their ability to derive several phenotypes from the same genotype. In higher ants, polyphenism can be extreme: high queen–worker size dimorphism and worker polymorphism allow for better success at colony founding by lone queens, better division of tasks, and ultimately access to new ecological nic...

All ants live in perennial colonies that exhibit three phases, namely foundation (initiation of new colonies), growth (production of more workers), and reproduction (production of sexuals). A greater understanding of colony life cycles is attained by contrasting the two main strategies of colony founding: independent and dependent colony foundation...

Division of labour improves fitness in animal societies. In ants, queens reproduce, whereas workers perform all other tasks. However, during independent colony founding, queens live as solitary insects and must be totipotent, especially in species where they need to forage. In many ants, solitary founding has been replaced by dependent founding, wh...

Division of labor is the essence of sociality in insects, and its most striking manifestation is the sterility of almost all colony members. Unequal reproduction among relatives is associated with many conflicts, and recent studies have reconciled these with kin selection (Bourke and Franks 1995). In this chapter, we examine the essential role of c...

Workers never mate in the large majority of ants, and they have usually lost the spermatheca, an organ specialized for long-term storage of sperm. Such 'non-sexual' workers are restricted to laying unfertilized eggs that give rise to males, and they cannot compete with the queens for the production of female offspring. In sharp contrast, workers in...

Offspring quality and quantity are subject to a trade-off. Depending on species, ant colonies can produce either numerous winged queens that start new colonies alone (independent colony foundation [ICF]) or one propagule consisting of reproductives helped by workers (fission). Some species do both. In the Rhytidoponera impressa group, colonies with...