Stenochrus portoricensis Chamberlin 1922

Stenochrus portoricensis Chamberlin, 1922

Figures 7–9

Stenochrus portoricensis Chamberlin, 1922: 11 –12. Reddell & Cokendolpher 1995: 110 (and references therein); Tourinho & Kury 1999: 3 –4, figs. 1–4; Armas 2004: 20, figs. 1.21A–D.

Diagnosis. Stenochrus portoricensis can be recognized by the presence of a row of two setae on the anterior process of propeltidium (Tourinho & Kury 1999: fig. 3), a mesal spur on the trochanter of pedipalp (Fig. 7) and by the characters of the internal genitalia of females. This species has spermathecae with two lobes similar in thickness, the median lobes two times as long as the lateral ones. Both spermathecal lobes have a wrinkled wall covered with small bumps (Fig. 8). For details on males, see Armas (2004).

Description. See Tourinho & Kury (1999).

Remarks. In most localities where this species has been collected, only females are known, suggesting several populations are parthenogenetic (Reddell & Cokendolpher 1995, Armas 2004). This seems to be the case of the population from Ilhéus, since no males were found in a large sample. Additionally, this species has been reported from disturbed places (e.g. Tourinho & Kury 1999) or associated with termite or ant nests in several localities (Reddell & Cokendolpher 1995). The records provided in the current study are consistent with both natural history patterns. The specimen from Ubatuba was collected under a rock in a lawn at a margin of a stream, a few meters from an urbanized beach (A.B. Buzatto, personal communication). Specimens from Ilhéus were all from abandoned nests of two arboreal termite species, Nasutitermes corniger (Motschulsky, 1855) and Nasutitermes sp. (Isoptera: Termitidae). The specimens were collected in ten nests, all of them abandoned and without any other species of termite. This suggests the termites can prevent the colonization of the nests since, from a total of 34 nests examined, 17 were still occupied by termites and none contained schizomids. Five nests with schizomids were found fallen on the ground, whereas the remaining five were still attached to cocoa branches, from 0.65 to 3.5 meters above the ground. The number of specimens in each nest varied from 1 to 38 (mean ± standard deviation: 11.8 ± 14.17). The variation of nest volume (0.01 – 0.07 m 3) has an effect on the number of schizomids collected (Linear Regression, F = 8.29, P = 0.01, R2 = 50.92). However, the result changed when two outlier nests with more than 30 individuals (whereas the remaining have no more than 14) were excluded (F = 0.0006, P = 0.97, R2 = 0.01). The position of the nest, whether on the cocoa branches or fallen on the ground, exerted no influence on the number (Mann-Whitney test, U = 8.5, P = 0.4) or density of individuals in the nests (U = 10.0, P = 0.6). Hence the colonization by S. portoricensis on termite nests in that area apparently occurs only after nest abandonment and is not influenced by the size or location of the nest. It is possible that interactions with other organisms associated with the nests, like woodlices, springtails, beetles or ants; could have some effect on the colonization and density of schizomids.

Distribution. Cosmopolitan, from USA to southeastern South America, West Indies, Canary Islands and England (Reddell & Cokendolpher 1995). In Brazil, restricted to southeastern and eastern Atlantic Forest, close to the coast (Tourinho & Kury 1999, Fig. 9).

Material Examined. BRASIL: Bahia: Ilhéus (Campus CEPLAC), 14o45’16”S 39o13’50”W, 27.II– 6.IX.2007, P.P. Santos coll., 118Ψ (IBSP 05–42); São Paulo: Ubatuba (Praia Dura), 23o30’S 45o10’W, 27.XII.2007, B.A. Buzatto coll., 1Ψ (IBSP 43).