Abundance and phenology of Schizomida (Archnida) from a primary upland forest in Central Amazonia.

There were 193 schizomids (hubbardids) collected from the soil (0–7 cm depth) during a 12 month study of a primary upland forest (37.5 6 16.8 ind/m2/month) near Manaus. They were represented by Surazomus brasiliensis (Kraus 1967) and an undescribed species of a new genus (96% and 4% of the total catch, respectively). About 68% of all specimens of S. brasiliensis inhabited the organic soil layer (0–3.5 cm depth) where monthly catches of juveniles were positively correlated with soil temperature. Females were twice as abundant as males. The lack of a distinct reproductive period and the presence of juveniles (in particular the first nymphal instar) and adults (both sexes) throughout the year indicate a plurivoltine mode of life. Few specimens were caught on the soil surface, and none were on tree trunks or in the canopy. Abundance of S. brasiliensis is compared to that of the Palpigradi (microwhip scorpions) and Thelyphonida (vinegaroons) from the same study site. The order Schizomida is comprised by about 180 described species. Few studies have been conducted on their ecology and biology. Schizomids are considered to be hygrophilous, photophobic, hemiedaphic inhabitants of soils, particularly in the tropics and subtropics. Some species are termitophiles, myrmecophiles, nidicoles or troglobites. (cf. Moritz 1993; Humphreys et al. 1989; Reddell & Cokendolpher 1995; Rowland 1972). In Central Amazonian forests, schizomids represent less than 1% of the soil arthropods which mostly inhabit the top 7 cm (cf. Adis et al. 1987, 1989). Our material, obtained in a primary upland forest over a 12 month period, represents the very first contribution on the abundance and phenology of a Neotropical schizomid species: Surazomus brasiliensis (Kraus, in Kraus & Beck 1967). STUDY AREA AND METHODS Schizomids were collected between 1981– 1983 in the course of ecological studies on Central Amazonian arthropods from a previously investigated and fully-described primary upland forest at Reserva Florestal A. Ducke (5 Reserva Ducke; 28559S, 598599W; Penny & Arias 1982). The reserve is located on the Manaus-Itacoatiara highway (AM–010), about 26 km from Manaus. The forest is subject to a rainy season (December–May: average precipitation 1550 mm; 258.9 6 36.8 mm/month) and a ‘‘dry’’ season (June–November: average precipitation 550 mm; 91.8 6 43.8 mm/month and each month with some rain events; Ribeiro & Adis 1984). The yellow latosol (5 ferrasol in Jordan 1984) of the primary upland forest had a 2–3 cm thick humus layer, interspersed with fine roots, and a thin surface covering of leaf-litter. One ground photo-eclector (emergence trap) and one arboreal photo-eclector for trunk ascents (funnel trap) were installed in the forest (cf. Adis & Schubart 1984) and remained there from December 1981 to December 1982. Distribution of schizomids in the soil was studied between September 1982 and August 1983 (Morais 1985). Twelve soil samples were taken once a month every 2 m along a randomly selected transect. The split corer, composed of a steel cylinder with lateral hinges (diameter 21 cm, length 33 cm), was driven into the soil by a mallet. Each sample of 7 cm depth was then divided into two subsamples of 3.5 cm each for extraction of animals, following a modified Kempson method (Adis 206 THE JOURNAL OF ARACHNOLOGY Figure 1.—Distribution of S. brasiliensis (Kraus 1967) (Schizomida), E. janetscheki Condé 1993 (Palpigradi) and T. amazonicus (Butler 1872) (Thelyphonida) in the soil. Samples taken monthly at 0–7 cm depth between September 1982–August 1983 in a primary upland forest near Manaus. (N 5 total number of specimens). Total precipitation per month given between sampling dates (5 at the end of each month). The low rainfall observed in early 1983 was due to a strong El Niño-event (cf. Adis & Latif 1996). 1987). The combined area of the 12 samples represented 0.42 m2. Calculated average abundances per m2 are given with sample standard deviation. The monthly collection data of schizomids from the two soil layers in relation to changing abiotic conditions (precipitation, temperature and humidity of the air near the forest floor; moisture content, temperature and pH of the soil) were statistically evaluated with a linear, parametric correlation test (Cavalli-Sforza 1972) using the original field data (Morais 1985). In addition, the presence of schizomids in tree crowns of the primary upland forest was tested by fogging canopies with pyrethrum during the dry and rainy seasons (August 1991–July 1994; cf. Adis et al. 1997a). All Schizomida sampled were classified as juveniles, subadults and adults (males and females, respectively; cf. Reddell & Cokendolpher 1995). Juveniles were tentatively assigned to three size classes, based on the length of the cephalothorax. The size classes presumably represent the three development stages in nymphs, apart from the subadult stage (cf. Brach 1976; Dumitrescu 1973; Rowland 1972). Voucher specimens have been deposited at the Systematic Entomology Collections of the Instituto Nacional de Pesquisas da Amazônia (INPA) in Manaus, Brazil, at the Texas Memorial Museum, Austin, Texas and at the Muséum d’histoire naturelle in Genève, Switzerland.