Experimental Housing for Montane Tiger Spiders — Poecilotheria smithi and P. subfusca: a preliminary report with comments on P. rufilata

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Problems with Keeping and Breeding Poecilotheria smithi and P. subfusca

The elevated humidity of the cool early morning and the afternoon fog is what the husbandry described in this article seeks to simulate. In 2004, myself and another American arachnoculturist were fortunate to get fertile eggsacs from Poecilotheria subfusca. However, our excitement was short-lived. I had in excess of eighty postembryos and, later, seventy-three 1st instars, yet lost every single spider during or just before their molt to 2nd instar. I had secondary problems from winged pests that forced me to move the 1st instars to a new incubating container, but I believe my difficulty in providing sufficient humidity and cool temperatures was the primary reason for failure. Meanwhile, the other American breeder had similar losses and was left with one lone survivor that he is raising. Several European breeders have fared better, and a limited number of captive bred P. subfusca have spread through Europe and been imported into the United States, but this remains a species that presents special problems in captive propagation.

The captive breeding of Poecilotheria smithi has proven even more difficult, and this species is extremely rare in captivity, especially in the United States. At the time of this writing in early January 2005, I have recently learned that an eggsac produced in the collection of a very well known European breeder of Poecilotheria has gone bad. The few eggsacs that have been produced in Europe have had a very small number of eggs. England's Ray Gabriel had a sac in 2004 that was eaten after thirteen days [Gabriel, 2004]. Interestingly, he also had two unbred females produce infertile "phantom" eggsacs. One female produced three phantom eggsacs throughout the year in January, March and October. A second female also produced a phantom eggsac in October.

Temperatures for Captive Husbandry of Poecilotheria smithi and P. subfusca

The idea that these montane species, particularly P. subfusca, should be maintained in conditions different than other Poecilotheria is not a novel one. In fact, Smith et al. (2002) stated that it is likely "that a lack of awareness amongst arachnoculturists concerning the natural habitat of Poecilotheria subfusca, and particularly the low temperatures encountered by collectors, is one explanation why the captive breeding of this spider has only met with limited success".

In their book Mygales, Jean-Michel Verdez and Frederic Clétón commented on the difficulty in reproducing P. subfusca and recommended maintaining both males and females at 55-57°F [13-14°C] with reduced feeding for two months to condition them for breeding [Verdez & Clétón, 2001]. However, these authors emphasized that this cooling period was necessary for wild-caught spiders and not needed or recommended for captive bred specimens. For the latter they suggested a distinct difference in summer and winter temperatures: 68°F [20°C] at night and 73.4°F [23°C] during the day in winter and 78.8°F [26°C] and 86°F [30°C], respectively, night and day in summer. Based on the weather data presented above, I cannot agree with these high summer temperatures and personally avoid any temperatures in excess of 80°F [27°C]. However, it is likely that acclimated captive bred spiders will tolerate temperatures above those encountered by their wild ancestors.

Peter Klaas' Vogelspinnen also remarked on difficulties maintaining Poecilotheria subfusca and stressed that neither constantly high nor low temperatures are advisable [Klaas, 2003]. He maintains his specimens at 68-72°F [20-22°C] and has acclimated wild-caught spiders at 64.5°F [18°C].

Experimental Housing for Poecilotheria smithi and P. subfusca

Providing appropriate temperatures and humidity levels for captive arachnids [as well as reptiles and other exotics] can become quite a balancing act, especially in the case of humidity, where improper techniques can result in overly damp conditions and insufficient ventilation, which themselves lead to a host of problems. These include mold, fungi, bacteria and pests such as mites, phorid flies and fruit flies. Stagnant air, constant condensation and saturated substrate must be avoided, and I typically recommend that arachnoculturists err on the side of dryness as long as fresh drinking water is constantly available. Ventilation is of utmost importance. It must be remembered that even in the most humid forests air still circulates and periods of dryness, wind and changes in temperature all result in naturally fluctuating humidity conditions quite unlike the static dampness that may surround poorly housed tarantulas.

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