Polygonarea silvicola Lawrence, 1955

Dányi, László & Tuf, Ivan Hadrián, 2016, Out of Africa: The first introduced African geophilomorph centipede record from a European greenhouse (Chilopoda: Geophilidae), Zootaxa 4067 (5), pp. 585-588 : 585-587

Polygonarea silvicola Lawrence, 1955 ( Figures 1 –15)

Polygonarea silvicola Lawrence, 1955: 141 , Figs 6d–f

FIGURES 4–15. Polygonarea silvicola Lawrence, 1955: 4 , head capsule (forcipule and maxillae removed), ventral view; 5, distal part of mandible, antero-ventral view; 6, basal part of left antenna, ventral view; 7, labrum, ventral view; 8, clypeal area, ventral view; 9, forcipule, left side with ventral view, right side with dorsal view; 10, second maxillary telopodite, dorsal view (areolation drawn in part, same scale as for Fig. 11); 11, left side of maxillae, ventral view (areolation drawn in part); 12, first maxillary coxosternal lappet, ventral view; 13, 12th sternite, ventral view (areolation drawn in part, margin of stronger areolated area marked with dotted line); 14, posterior end of body, ventral view (setae on left leg omitted); 15, posterior end of body, dorsal view (setae of legs omitted).

Description of the specimen from Olomouc. Forty-nine leg-bearing segments, body length 29 mm. Habitus and colour of preserved specimen in alcohol as in Fig. 1 .

Antennae about 1.5 times as long as the cephalic plate, distally attenuate, with setae irregularly arranged on articles 1–2, and with some longer setae forming a rather irregular whorl on articles 3–4 as in Fig. 6. Cephalic plate about 1.5 times as long as wide, shape as in Fig. 2 and Fig. 4. Clypeus with four setae located on the clypeal area and two setae on the middle part, the remaining clypeal surface without setae (Fig. 4). Clypeal area as in Fig. 4 and Fig. 8, surface without areolation. Labral mid-piece with 6 sclerotized teeth, side pieces with about 11+12 membraneous fimbriae that are very delicate and almost transparent (Fig. 7). Mandible with a pectinate lamella of ca. 22 hyaline filaments, and with hyaline and more sclerotized (spine-like) fringes as in Fig. 5. First maxillae with well-developed lappets both on coxosternite and telopodites (Figs 11–12). First maxillar coxosternite without setae; coxal projections and telopodites as in Fig. 11. Second maxillae medially joined through a very narrow, hyaline and non-areolate isthmus only (Fig. 11), process of antero-internal corners of coxosternum well developed (Fig. 11). Second maxillary coxosternum and telopodites with setae and apical claw as in Figs 10–11. Epipharynx with 6 pores.

Forcipular segment: when closed, the telopodites over-reach the anterior margin of the head ( Fig. 2 ). Forcipular tergite trapeziform, with anterior margin concave (Fig. 9). Coxosternum with incomplete chitinous lines, middle part of the anterior border with two denticles, ochreous in colour (Fig. 9). Trochanteroprefemur with a well developed tooth on the distal part of the medial edge, femur and tibia unarmed, tarsungulum with a denticle (Fig. 9). Posterior edge of the ungular blade weakly serrulate. Calyx of poison gland and chaetotaxy of forcipule as in Fig. 9.

Sternites with pore fields present from the first to the penultimate sternite. Four groups of pores on sternites 1–46 as in Figs 9 and 13, and in two subsymmetrical areas on sternites 47–48 (Fig. 14). Anterior ca. 16–17 sternites with posterior triangular protuberance running under the next segment’s metasternite (Figs 9, 13), especially well developed and sclerotized in sternites 1–3 (Fig. 9). Sternites with medial longitudinal depression ( Fig. 3 ) and with stronger areolation in this part (Fig. 13).

Ultimate leg-bearing segment without separate intercalary pleurites (Fig. 15). Ultimate presternite divided along the sagittal plane (Fig. 14). Shape and chaetotaxy of tergite and sternite as in Figs 14–15. Ultimate coxopleura with a distinct protuberation at their distal ventral margin, tightly covered with numerous small setae similarly to the ultimate sternit’s posterior part (Fig. 14). Six and seven coxal pores close to the sternal margin and partly covered by the sternit, opening separately but grouped in a weakly developed longitudinal depression (Fig. 14). Ultimate legs composed of seven articles with ratios and ventral chaetotaxy as in Fig. 14. Ultimate pretarsus represented by a claw (Fig. 14). Postpedal segments as in Figs 14–15, gonopods uniarticulate, anal pores present.

Remarks on morphology. P. silvicola was known till now from only one specimen, the female holotype. Our specimen fits well the detailed original description given by Lawrence (1955) and only differs in the following characters: 1) number of pairs of legs is 49 versus 55 in holotype; 2) 6 teeth on labral mid-piece versus 7–8 in holotype;. 3) 1+1 setae on the middle part of clypeus versus 2+ 4 in holotype.

The difference in the number of pairs of legs can be explained by individual variability, since similar intraspecific differences were found in other species ( Lawrence 1955). The number of clypeal setae and labral teeth increases with age in many species of Geophilidae , thus the probably younger stadium of the studied specimen (indicated also by its smaller size) might explain the differences in these features. Although the arrangement of setae on the basal antennal articles does not fit silvicola in the key given by Lawrence (1955) for the genus, it is in agreement with the text of the original description published in the same paper.

Figures

FIGURES 1 – 3. Polygonarea silvicola Lawrence, 1955: 1, habitus, dorsal view; 2, head, dorsal view; 3, sternites 7 – 10, ventral view.