Phragmosis

Corythomantis greeningi Anurans involve a diverse group of largely carnivorous, short-bodied, tailless amphibians. Within this group, some frogs are characterized by a peculiar casqued head, with the skin co-ossified with the underlying bones. This type of skull is generally associated with phragmotic behaviour, where the animal will enter a hole and block the entrance with its head. == In gall-forming aphids ==

The aphid Astegopteryx sp. exhibits a head-plugging defense by forming a banana-bunch shaped gall, consisting of several subgalls, on Styrax benzoin. The soldier aphids of Astegopteryx are characterized by their sclerotic, protruded heads, covered in many spine-like setae. Several soldiers cooperate with one another to plug the ostiole of the subgall, utilizing their specialized morphology. In a study by Kurosu et al. (2005), of 173 ostioles examined, 90.8% were plugged, with no space among the guarding soldiers. Of the 90.8% plugged ostioles, several male intruders were found outside the phragmotic plug, attempting to enter. All intruders were blocked by the guarding soldiers, and it was nearly impossible to enter the subgall. Astegopteryx soldiers effectively defend their subgall by plugging the ostiole nearly completely with their sclerotic, spiny heads, which are very likely to have evolved for that purpose. == In ants ==

Phragmotic-headed ants prevent intruders from entering nests by blocking the entrances, or by pushing them out of entrance galleries. Within the Neotropical species, Blepharidatta conops, queens are characterized by shield-like heads, and appear to secrete fibrous material. The material acts as a coating and eventually accumulates into a dense tangle of material, creating a disk over the head. When nests are visited, or inhabited by predators (especially beetles), the entrance is quickly blocked by the peculiar phragmotic disk of the queen. This modification of the body enables the queen to act as a living gate to the brood chamber. Colobostruma Wheeler (C. leae), Crematogaster Lund (Colobocrema), Pheidole Westwood (P. colobopsis, P. lamia), but also in other genera, such as Blepharidatta Smith, (B. conops), Tetraponera Smith (T. phrag- motica) and Carebara Westwood. The behaviour is most developed in the genus Cephalotes, where all castes (both queens and workers), have highly adapted head morphologies. The shield-like armor which characterizes this behaviour enables plugging of nest entrances, without exposing eyes, antenna or mandibles to any potential intruders. == In spiders ==

'' The trapdoor spider Cyclocosmia has an abdomen ending in a hardened disc that it uses to plug the entrance to its burrow. == References ==