A taxonomic revision of the tribe Aganippini (Ctenizidae) is made. The
genus Blakistonia Hogg is excluded from the tribe, Gaius Rainbow is synonymized
with Anidiops Pocock, and Eucyrtops Pocock is re-instated. The group now consists
of the four genera Aganippe Cambridge, Idiosoma Ausserer, Anidiops, and
Eucyrtops. The former 23 species of the tribe are reduced to nine, and three new
species are described, making a total of 12 valid species. Allotypes of five species,
previously known only from one sex, are designated and described.
Many characters customarily used in mygalomorph taxonomy are criticized
and shown to be inadequate.
Observations on the life histories and natural history of the species are
recorded. The adaptive function of different burrow and door structures is discussed.
Distribution of species in relation to particular habitat types in the general
environment is mentioned. Parallel adaptation of a specialized foraging behaviour
("twig-lining", whereby spiders attach twigs to the rim of the burrow in such a
way that they are utilized as "feeling lines" when foraging) is recorded for seven
species in three genera. Twig-lining appears to be an adaptation to relatively dry
habitats where the food supply is less abundant. By this method of foraging,
animals increase their area of search for food.
A relationship between morphology and behaviour is noted. Certain morphological
features, in particular the eyes, are shown to be correlated with burrow
structure, including door type, and foraging behaviour.
The evolutionary radiation of the tribe is shown to be the result of ecological
expansion. Postulated phylogeny of the tribe is outlined.
Derivation of the genus Idiosoma from Aganippe is postulated. It is suggested
that this has been due to "block" inheritance of several characters (which together
have adaptive superiority), and which are assorting independently in other species.
These characters, when inherited together, mark the irreversible culmination of
the adaptive trend of twig-lining, the initial stages of which are exhibited by the
adaptively plastic species of Aganippe and Anidiops.
Soil preference and burrow structure of an endangered tarantula, Brachypelma vagans (Mygalomorphae: Theraphosidae)