Taxonomy
The family Dictynidae was created by O. Pickard-Cambridge in 1871 to segregate a group of small spiders furnished with cribellum and calamistrum, whose general aspect would previously locate them among the Agelenidae. The later genesis of the “cribellatae” group (Bertkau, 1882), followed by Thorell (1886), Simon (Histoire Naturelle des Araignées, 1892) and others, kept them far from their original family. Such was the way they were catalogued by Bonnet in his Bibliographia Araneorum (1955-59) and Roewer in his Katalog der Araneae (1954), with a total 31 and 36 genera respectively.
The true evolutionary significance of the cribellum was subject to great discussion during all the XX century. Regarding the Dictynidae, we have to undoubtedly refer to the work by Lehtinen (1967); in it he established a new range for the family by including a series of genera previously located at the Cybaeinae and also some Ageleninae. Those are spiders that have lost the cribellum, but where the basic pattern of the male and female in genitalia, besides other characters, is close to the traditional Dictynidae. The existence of evolutionary lines where both cribellate and ecribellate forms are present is the principle behind Lehtinen's proposed readjustment of all the Araneomorphae, with particular attention to amaurobiform spiders. Apart from lesser details, this proposal for the Dictynidae is still valid today and is reflected in the last catalogue by Platnick (2005), which includes 48 genera and more than 500 species all over the world.
In the Spanish spider catalogue by Fernández Galiano (1910), in the family Dictynidae, which also includes Amaurobius C.L. Koch, 1837, four genera are mentioned (Chaerea Simon, 1884, Devade Simon, 1884, Dictyna Sundevall, 1833, and Lathys Simon, 1884); nevertheless, some species under the genus name Dictyna appear nowadays part of genera created at a later time, as in the case of Ajmonia Caporiacco, 1934, Marylinia Lehtinen, 1967 and Nigma Lehtinen, 1967. Fernandez Galiano also mentions Tetrilus Simon, 1886 (now Mastigusa Menge, 1854) and Chorizomma Simon, 1872, both in the family Agelenidae. Altella Simon, 1884, Archaeodictyna Caporiacco, 1928 and Argenna Thorell, 1870, have been mentioned subsequently.
Morphology
The dictynidae are provided with cribellum and calamistrum (cribellate spiders), although they may have lost them secondarily (ecribellate genera); they have complex genital organs (differentiation of the epygine in females and complex copulatory bulbs in males); the chelicerae have a typical labidognath disposition (Araneomorphae); their respiratory organs consist of a pair of lungs and a tracheal system, whose unique opening is immediatly in front of the spinnerets; the leg tips have three tarsal claws (trionycha). In subterminal position, at the ventral face of the abdomen, close to the anal tubercle, six spinnerets are present; anteriors and posteriors show a similar size; the latter have a second article, small and conical.
In their carapace it is easy to tell head and thorax apart; the first, narrower, of paralel sides, and the second somewhat flatter and of rounded borders, showing a central fovea, which is reduced or even absent in some cases. The eight eyes are in two transversal rows subject to some procurve or recurve distortion, but no more than two rows are ever present (in Chorizomma the MA eyes are absent, so they only have six: 2,4); their sizes are rather similar, although in some cases the relation between diameter and separation is used as a diagnostic character (in Lathys the MA eyes are clearly smaller).
The chelicerae are large and robust, with teethed margin; in some species the males present a prismatic and sinuous base, so that a characteristic central open space between them is left. The cribellum may be divided (in two transversal plates) or not, and the calamistrum consists of a large series of hairs at the apex of the metatarsus IV, easy to notice. They are small spides, with a characteristic coloration.
Biology
The Dictynidae are sedentary spiders that build irregular and loose mat webs made of ordinary and calamistrum silk intermixed. In some species, the first lines have an irregular radial disposition, finishing in a round web. The spider stays below it upside down.
Their habitat is much varied; there are lapidicoles that can dwell in urban habitats, but more often they live in woods taking advantage of little holes in ground litter or using leaves and the softest tips of bush branches to build their webs.
Females may have one or more eggsacs, that they put side by side inside their own web. The eggsac is lens or disc-shaped with two cover layers, the internal rather loose and the external more narrowly woven.
Present iberian diversity
- Ajmonia Caporiacco, 1934 (1sp.)
- Altella Simon, 1892 (1sp.)
- Archaeodictyna Caporiacco, 1928 (1sp.)
- Argenna Thorell, 1869 (2spp.)
- Chaerea Simon, 1884 (1sp.)
- Chorizomma Simon, 1872 (1sp.)
- Devade Simon, 1884 (1sp.)
- Dictyna Sundevall, 1833 (5spp.)
- Lathys Simon, 1884 (4spp.)
- Marilynia Lehtinen, 1967 (1sp.)
- Mastigusa Menge, 1854 (1sp.)
- Nigma Lehtinen, 1967 (4spp.)
Author: José Antonio Barrientos (2005)
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