Amblypygi, Arachnida, Arthropoda, Animalia
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Range
The previous range of Phrynus parvulus included locations in Guatemala and Belize (Quintero, 1981). This page adds Costa Rica to the range.
Identification
Phrynus parvulus is recognized as having one spine in between the two longest spines on the dorsal surface of the pedipalpal tibia as well as pedipalps that are covered with short club-like sensilla that can be seen under a dissecting scope. Young individuals typically have reddish palps with banded legs while large adults are more uniformly colored.
Natural History
Phrynus parvulus has previously been collected from locations in Guatemala and Belize and nothing was known of its natural history. It has just recently been discovered in the tropical forest surrounding La Selva Biological Station in Costa Rica. This species, like all amblypygids, is nocturnal. During the day, individuals tend to reside in a variety of places associated with large buttressing tree trunks. They have been found deep in crevices on the trunks, in the buttressing near the bases, in burrows or other holes at the base of large trunks, and sometimes behind bark. Typically only one individual resides in a crevice, however, I have noted on a few different occasions a crevice being inhabited by both a male and a female. There can often be up to 13 or more different individuals residing on one tree trunk.
Preliminary field observations suggest that males move their diurnal resting location (i.e. the crevice from which they emerge) significantly more often than females, suggesting that females may be more sedentary and males may wander in search of a mate. I have occasionally observed males crawling along the forest floor presumably in search of a new tree. Phrynus parvulus seems to have a more or less continual breeding season as I have observed females with eggs in January as well as June through August. Once mated, a female may take a few months before she lays her eggs and once laid, she carries them underneath her abdomen for up to 3 months. When the young hatch, they crawl onto the mother's back and reside there for 6-8 days until they molt one more time and disperse from the mother. Female P. parvulus can have up to 40 young at a time.
All amblypygids are predatory and P. parvulus has been seen in the field eating crickets, moths (which were caught out of the air), and small millipedes. They tend to avoid scorpions, centipedes, large ctenids (wandering spiders), and virtually all ants. Individuals come out of their crevices at dusk and usually do not stray very far, returning to their crevice at dawn. They can be readily seen sitting stationary on the vertical trunks of trees after dark. They are relatively common in the arboretum at La Selva and if one is wanting to see these incredible creatures, that is the place to look.
Interactions among individuals seems to be relatively rare; at least in my observations. The few interactions that I have witnessed have been between two males (aggressive interactions) or between males and females residing in the same crevice. I have not yet been able to witness courtship or spermatophore deposition in the field. When males meet in the absence of a female, they seem to have a ritualized posturing display which involves opening one palp, raising their bodies in the air, and holding that position. However, if a female is involved, they engage in actual combat. Two males in the field have been seen to lock their chelicerae and palps together and fight more or less continually for more than an hour and a half!
Although these animals may look extremely dangerous and frightening, they are in fact harmless. Unlike spiders, amblypygids do not have any vemon glands. They are rather docile creatures that are easily frightened. In response to potential threats, amblypygids use their speed for escape and I have never had Phrynus parvulus engage in a threat posture towards me.
Literature Cited
Quintero, D. Jr. 1981. The amblypygid genus Phrynus in the Americas (Amblypygi, Phrynidae). J. Arachnol. 9: 117-166.
Page author:
Eileen Hebets, Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721. ehebets@u.arizona.edu
Web page assistance:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu