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. Luis Eduardo Acosta . Harvestmen (Arachnida) from Argentina and neighboring countries .

Although frequently found, for most people in Argentina harvestmen (Order Opiliones) are almost unknown: they are confused with spiders. These arachnids are principally nocturnal, and hide during the day under stones, bark, etc. Despite of the bizarre appearance of some species, harvestmen are by no means poisonous, but all bear a pair of repugnatory glands instead, whose role is presumably defensive. The characteristic smell produced by species of genus Pachyloidellus gave them vernacular names like "chinchina" or "chichina" (in Spanish, "chinche" is applied to heteropteran bugs).

Harvestmen show a striking diversity of shapes, sizes, and habits. In available textbooks -normally published in the Northern Hemisphere- opilionids are often mentioned, but there mostly long-legged species of the Suborder Palpatores are shown; such harvestmen are common in Europe and North America, but are not so frequent in the local fauna. Here the Laniatores are dominant, especially the speciose family Gonyleptidae, a taxon restricted to the Neotropics.

Click on the image and you will enter the site Opiliões na Web, interesting introduction to the morphology, the systematics and the biology of the Order.

Pachyloidellus fulvigranulatus (male)

Most gonyleptids are robust, especially in the subfamilies Gonyleptinae and Pachylinae. Sexual dimorphism in this group is remarkable, being typical for males (photo on the left) the strong apophyses on the fourth pair of legs; in the females all legs are unarmed.
In Argentina more than 60 % of the opiliofauna belongs to the Gonyleptidae.

If you click here you will see females Pachyloidellus goliath while guarding their eggs; this is quite uncommon for the whole order, but more and more gonyleptids are being reported to exhibit such behaviour.

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The Argentinian opiliofauna contains tiny, delicate forms like Acropsopilio chilensis or Ceratomontia spp., and the order's giants as well (Pachyloidellus goliath, Sadocus polyacanthus). The highest local diversity is detected in the three areas with highest precipitations and with most developed humid forests: the andean-patagonic forests, the "yungas" (montane rainforests of the NW), and the rainforests of Province of Misiones. See also the Checklist of the Argentinian harvestmen.

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Research:

The author works basically on the systematics and zoogeography of Gonyleptidae Pachylinae of Argentina and neighboring countries (Chile, Perú, Uruguay, southern Brasil). Other harvestmen taxa are also considered in faunistical surveys. Genera of central Argentina, like Neopucroliella and Pachyloidellus have been reviewed. In the moment, two closely related projects are in progress:

Systematics and distribution of harvestmen of NW Argentina
This project is based on methodic samplings in the Argentinian yungas, which have been carried out along several years.The revisionary work is focused on genus Pachyloides, dominant in this area.

Revision of the opiliofaunas of Perú and Bolivia
As a continuation of the above mentioned project, the revision of genera related to the "Andean Corridor" was undertaken; this includes harvestmen of the yungas and the puna, as well as species of related areas. The research is based chiefly on the study of several collections, but samplings in the Departamento del Cusco (Perú) have been also carried out. In a first step, the genera Acrographinotus and Polyacanthoprocta are being revised.

Publications of the author on Opiliones
Information on type material (species authored by L.E. Acosta)
Photo gallery

Background: male Pachyloidellus goliath Acosta

The Arachnology in Argentina