Page 1 of 6 | by William Korinek, Bruce Effenheim & Michael Jacobi
The tarantula spider Poecilotheria subfusca has proven to be a problematic member of the genus to successfully breed in captivity. It is a montane species from the Central Highlands of the island country Sri Lanka, and at least one population (Nuwara Eliya) inhabits a very cool climate where afternoon fogs are common and overnight lows may reach freezing (Smith, Carpenter & Lamoreux 2000, Jacobi 2005). Three distinct biotopes are presently known to harbor this species (Ray Gabriel, pers. comm., Jacobi). In addition to the highland Nuwara Eliya form, two lower elevation populations are found in the vicinity of Kandy and Matale. It is unknown if the specimens in the tarantula hobby are represented by more than one population, but the success the authors have had breeding the species, while employing pre-breeding and post-breeding conditioning approximating a cool, moist high-altitude climate, suggests that their spiders are of Nuwara Eliya origin. These spiders also have a very dark coloration with a near-black venter, which is presumably an adaptation for absorbing heat quicker when the sun warms the mountain air.
Smith et al. (2002) detailed the montane habitat of P. subfusca with emphasis on the low temperatures found in the Central Highlands of Sri Lanka. Kirk (1993) also commented on the cool climate. Although Poecilotheria subfusca has only recently become widespread in US tarantula collections, this species has been a part of European arachnoculture for some time. Verdez and Clétón (2001), Striffler (2002), and Klaas (2003) all commented on the cool temperatures required for successful captive husbandry. Smith et al. (2002) stated that one explanation for the limited success of captive breeding this spider is likely a lack of understanding its natural habitat. P. subfusca is found above the tea plantations in secondary scrub forest and remnants of montane forest. This spider inhabits hole retreats in dead trees sometimes enveloped by fog. Even during the warmest months, February and March, temperatures rarely exceed 70°F [21°C], and during September the early morning hours may be as cool as 40°F [4°C] at elevations near 6500 ft [2000 m]. The village of Nuwara Eliya rests at 6168 ft [1880 m] above sea level and seven degrees north of the equator [6¼58' n; 80¼46' e]. Weather data recorded there over a number of years reveals average daily maximum temperatures of 65-71°F [18-22°C] and minimums of 44-55°F [7-13°C]. In a nine-year period the highest recorded temperature was 78°F [26°C] in March and the lowest was 27°F [-3°C] in January. Sri Lanka's precipitation is related to the Asiatic monsoons and there are two rainy seasons: April to June and October to November. During these periods average monthly rainfall at Nuwara Eliya is 10-12 in [250-300 mm]. However, the relative humidity remains high throughout the year, even during the driest months. Although the average monthly precipitation during February is only 1.7 in [43 mm], early morning humidity is still about 85% and late afternoon humidity averages 65%. Annual relative humidity at 0800 hours is 84-91% and at 1700 hours is 66-86%. During a lecture at the 2003 American Tarantula Society conference Andrew Smith commented on being able to see one's breath in the morning and fog rolling in during late afternoon where he has found P. subfusca.
The first known fertile Poecilotheria subfusca egg sac in the United States was produced in the collection of John LaRizzio of Philadelphia. LaRizzio introduced a mature male that had built a sperm web on 5 September 2003 to his female in mid-September 2003. The male initiated courtship and the female was very receptive. However, insertion of palpal emboli was never witnessed, and the male's mating attempts were off target, with his pedipalps sometimes reaching as far back as the female's spinnerets. The male was removed and reintroduced approximately one week later. This time the female approached very quickly, without any body undulations or other behavior that would suggest courtship. In LaRizzio's past experience breeding other Poecilotheria species, this action usually preceded the male being attacked and eaten, so the spider was removed again. By the first week of October, LaRizzio had decided to place the male in the female's enclosure and leave him, regardless of outcome. Mating was not observed, but the male was still alive the following morning and was again removed.
Within a short time the female had secured a position in a cork bark retreat and ceased to feed. On 10 November 2003, she began to construct an egg sac. This was quite a surprise for LaRizzio as his experience breeding other Poecilotheria species, this action usually preceded the male being attacked and eaten, so the spider was removed again. By the first week of October, LaRizzio had decided to place the male in the female's enclosure and leave him, regardless of outcome. Mating was not observed, but the male was still alive the following morning and was again removed.
Within a short time the female had secured a position in a cork bark retreat and ceased to feed. On 10 November 2003, she began to construct an egg sac. This was quite a surprise for LaRizzio as his experience breeding other Poecilotheria had shown that as much as nine months would elapse between mating and egg sac production. The egg sac was taken from the female for artificial incubation approximately 26 days later.
Unfortunately, on 21 January 2004, LaRizzio reported on Arachnoboards.com that of the thirty or so eggs only two postembryos had successfully reached 1st instar. Of these two survivors, only one made it to adulthood, a male that since has matured and died of old age.