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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 exclusion, gas exchange and defense. Entrance funnels are relatively impermeable and divert water from nests, but simple tubes would achieve the same result. Consistent with the gas exchange hypothesis, projected funnel entrances likely increase gas exchange rates over sixfold compared to simple tubes and may increase air flow within the nest. Gas exchange may explain the recurrent evolution of funnel entrances in several ant lineages, especially among cliff dwelling species. We outline M. sofina defense responses to conspecifics and co-occurring ant species, and find no support for a defense role of entrance funnels. Workers display little aggression but respond to several species with an original form of nest defense––cliff jumping—in which workers drop off the cliff face while clinging to invaders and then return to their nest. M. sofina is a restricted range species under threat of extinction by habitat destruction. Its novel lifestyle underscores the urgency of exploration and conservation in a tropical biodiversity hotspot.

Winged queens are the most common reproductives in ants. They are morphologically specialized for independent colony foundation, with wings for long-range dispersal and metabolic reserves to raise the first brood. However independent foundation can sometimes be selected against and replaced by fission, featuring short-range dispersal on the ground and reproductives that are dependent on the wingless workers for all non-reproductive tasks. We investigated the evolutionary consequences of this transition on the morphology of the reproductives by collecting 30 colonies of Odontomachus coquereli from Madagascar, the only species in the genus where winged queens have never been found. Data about colony demography, morphometry, allometry and ovarian dissections showed that the winged queen caste has been replaced by a wingless reproductive caste with distinct body proportions relative to the workers or to congeneric winged queens. The 17 reproductives that we measured exhibited little size variability. A single wingless reproductive was found in each colony, corresponding to ‘ergatoids’ in literature. Several facts suggest that colonies reproduce by fission, notably the relatively constant colony size (19±11 workers). The developmental origins of wingless reproductive phenotypes need investigation; little genetic change may be involved, as seen when Odontomachus larvae are parasitized by nematodes. The sole function of wingless reproductives in O. coquereli is reproduction, and they contrast with multi-purpose wingless reproductives found in other ants, where numerous intermorphs occur in each colony and contribute to sterile tasks.

In montane fynbos in South Africa Melissotarsus emeryi Forel was found nesting in live wood of Leucospermum praemorsum (Meisn.) E. Phillips, in association with armor-scale insects (Diaspididae). A loose network of silken material was found along gallery tunnels and was combined with wood particles to seal cracks in tunnel walls and to close exit holes. Our observations reveal that the silk is produced by adult workers from glands located in cuticular depressions on the ventral portion of the anterior margin of the hypostoma. Silk was applied in nest construction with the aid of modified protarsi in the form of “silk brushes.”M. emeryi is the only adult Formicidae known to produce silk and is the only record of silk production at any life stage in the Myrmicinae. We discuss silk production in Melissotarsus in relation to nest construction, defense, and diaspidid symbionts.

Summary In northern California, ant assemblages in 8 sites in serpentine chaparral habitat were compared with those occurring in 8 chaparral sites on adjacent non-serpentine soils. A total of 27 species of ants was found: 22 species were collected in non-serpentine chaparral and 20 species in serpentine chaparral. Seven species were collected exclusively in non-serpentine, and 5 species were found only in serpentine habitats. A Formica species, conspecific with or closely related to F. xerophila, was found only in serpentine chaparral. Subsequent collections suggest that in northern California, this species is confined to serpentine outcrops. Two other species significantly differed in frequency of occurrence in each habit: Camponotus hyatti, C. cf. vicinus. Five species showed marginal significant differences in their relative abundance between habitats: Camponotus hyatti, C. cf. vicinus, Formica moki, Prenolepis imparis, Leptothorax nevadensis, Stenamma diecki.