A new type of exocrine gland and its function in mass recruitment in the ant Cylindromyrmex whymperi (Formicidae, Cerapachyinae)

Colony expansions underlie the evolution of army ant mass raiding

The mass raids of army ants are an iconic collective phenomenon, in which many thousands of ants spontaneously leave their nest to hunt for food, mostly other arthropods. While the structure and ecology of these raids have been relatively well studied, how army ants evolved such complex cooperative behavior is not understood. Here, we show that army ant mass raiding has evolved from a different form of cooperative hunting called group raiding, in which a scout directs a small group of ants to a specific target through chemical communication. We describe the structure of group raids in the clonal raider ant, a close relative of army ants in the subfamily Dorylinae. We find evidence that the coarse structure of group raids and mass raids is highly conserved and that all doryline ants likely follow similar behavioral rules for raiding. We also find that the evolution of army ant mass raiding occurred concurrently with expansions in colony size. By experimentally increasing colony size in the clonal raider ant, we show that mass raiding gradually emerges from group raiding without altering individual behavioral rules. This suggests that increasing colony size can explain the evolution of army ant mass raids and supports the idea that complex social behaviors may evolve via mechanisms that need not alter the behavioral interaction rules that immediately underlie the collective behavior of interest.

Novel thoracic glands in the ant Myopias hollandi

Besides the common labial and metapleural glands, four novel exocrine glands are described in the thorax of both workers and queens of the ponerine ant Myopias hollandi. From anterior to posterior, these glands were designated as the propleural pit gland, the posterolateral pronotal gland, the anterolateral propodeal gland and the metasternal process gland. They all correspond with class-3 glands, that are made up of bicellular units that each comprise a secretory cell and a duct cell. In the propleural pit gland, the ducts are characterized by a gradually widening diameter, while in the three other glands the ducts show a portion which displays a balloon-like expansion, that on semithin sections stains very dark. For none of these novel glands the function is known as yet, although ultrastructural examination indicates that they produce a non-proteinaceous and therefore possibly pheromonal secretion.

Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae)

The generic classification of the ant subfamily Dorylinae is revised, with the aim of facilitating identification of easily-diagnosable monophyletic genera. The new classification is based on recent molecular phylogenetic evidence and a critical reappraisal of doryline morphology. New keys and diagnoses based on workers and males are provided, along with reviews of natural history and phylogenetic relationships, distribution maps, and a list of valid species for each lineage. Twenty-eight genera (27 extant and 1 extinct) are recognized within the subfamily, an increase from 20 in the previous classification scheme. Species classified in the polyphyletic Cerapachys and Sphinctomyrmex prior to this publication are here distributed among 9 and 3 different genera, respectively. Amyrmex and Asphinctanilloides are synonymized under Leptanilloides and the currently recognized subgenera are synonymized for Dorylus. No tribal classification is proposed for the subfamily, but several apparently monophyletic genus-groups are discussed. Valid generic names recognized here include: Acanthostichus (= Ctenopyga), Aenictogiton, Aenictus (= Paraenictus, Typhlatta), Cerapachys (= Ceratopachys), Cheliomyrmex, Chrysapace gen. rev., Cylindromyrmex (= Holcoponera, Hypocylindromyrmex, Metacylindromyrmex), Dorylus (= Alaopone syn. n., Anomma syn. n., Cosmaecetes, Dichthadia syn. n., Rhogmus syn. n., Shuckardia, Sphecomyrmex, Sphegomyrmex, Typhlopone syn. n.), Eburopone gen. n., Eciton (= Camptognatha, Holopone, Mayromyrmex), Eusphinctus gen. rev., Labidus (= Nycteresia, Pseudodichthadia), Leptanilloides (= Amyrmex syn. n., Asphinctanilloides syn. n.), Lioponera gen. rev. (= Neophyracaces syn. n., Phyracaces syn. n.), Lividopone, Neivamyrmex (= Acamatus, Woitkowskia), Neocerapachys gen. n., Nomamyrmex, Ooceraea gen. rev. (= Cysias syn. n.), Parasyscia gen. rev., †Procerapachys, Simopone, Sphinctomyrmex, Syscia gen. rev., Tanipone, Vicinopone, Yunodorylus gen. rev., Zasphinctus gen. rev. (= Aethiopopone syn. n., Nothosphinctus syn. n.).

Current knowledge on exocrine glands in carabid beetles: structure, function and chemical compounds

Many exocrine products used by ground beetles are pheromones and allomones that regulate intra- and interspecific interactions and contribute to their success in terrestrial ecosystems. This mini-review attempts to unify major themes related to the exocrine glands of carabid beetles. Here we report on both glandular structures and the role of secretions in carabid adults, and that little information is available on the ecological significance of glandular secretions in pre-imaginal stages.