Acerentulus apuliacus Rusek & Stumpp, 1988

Acerentulus apuliacus Rusek & Stumpp, 1988

Figs. 1‒22 View FIGURES 1 – 9 View FIGURES 10 – 13 View FIGURES 14 – 22 , Tables 1 View TABLE 1 , 2 View TABLE 2

Acerentulus apuliacus Rusek & Stumpp, 1988:153

Material examined. Type specimens not available. Examined material: 4 males, 19 females, 4 pre-imagos, 13 maturus juniors and 2 larvae II from litter ( feuilles mortes) collected west of Rionero in Vulture ( Potenza Province, Basilicata, Southern Italy), 600 m elev., 25 August 1983, coll. S. Vit ; 1 male and 1 female collected from litter at the base of a maple ( Litiére /pied pourri d’Acer) in Vieste ( Foggia province, Apulia, Southern Italy). These specimens deposited in the collection of Geneva Natural History Museum.

Redescription. Body length 1149 ± 125 µm (range: 904–1366; n = 23). Head 135 ± 13 µm long (range 119–182; n = 24); setae sd4 and sd5 present, seta d6 ( Rusek et al. 2012) absent ( Fig. 1 View FIGURES 1 – 9 ). Rostral setae r1 and r2 nearly 10 µm long, labral seta lb 1.5 times longer than rostral setae ( Fig. 2 View FIGURES 1 – 9 ). Single frontal pore anterior to level of pseudoculi ( Fig. 3 View FIGURES 1 – 9 ). Rostrum very short. Pseudoculus slightly elliptic, 9 µm long (range: 8‒11; n = 24), longitudinally divided ( Fig. 4 View FIGURES 1 – 9 ); PR = 14.6 (range 12.2–18.2, n = 23). Proximal part of maxillary gland long and terminally dilated ( Fig. 5 View FIGURES 1 – 9 ), length 26 µm (range: 22–32; n = 23), CF = 5.2 (range: 4.3–6.3; n = 22). Maxillary palpus with slender setaceous sensilla ( Fig. 6 View FIGURES 1 – 9 ). Labial palpus with distinctly thickened sensillum ( Fig. 7 View FIGURES 1 – 9 ).

Foretarsus length 88 ± 3 µm (range: 78–92; n = 22), claw 24 µm (range: 22–26; n = 18), without inner tooth, TR = 3.6 (range 3.4–4.0; n = 18); empodium length 5 µm (range: 4–6, n = 10), EU = 0.19 (range 0.16–0.24, n = 10); S-shaped seta longer than claw, 28 µm (range: 25–32; n = 10). Sensillum t1 claviform, BS = 0.35 (range 0.27–0.42, n = 22); t2 thin, t3 proximally dilated. Sensillum a long, distinctly broadened basally, passing base of seta γ3; sensilla b‒g slender, long; b, c and d of equal length; sensilla b and c reaching the base of e, sensillum d reaching the base of f, sensilla e and f almost of equal length, not reaching the empodium, sensillum g passing the base of claw, f nearer to e than to g ( Fig. 8 View FIGURES 1 – 9 ). Sensillum a’ broad, barely reaching the base of b’, b’ and c’ almost of equal length and thin, the apex of c’ reaching the empodium ( Fig. 9 View FIGURES 1 – 9 ). Ventral seta β1 very short, barely reaching the base of δ2; δ4 situated more proximally than sensillum c’. Foretarsal pores present near the bases of sensilla c and g ( Fig. 8 View FIGURES 1 – 9 ). Middle tarsus length 37 µm (range: 34–39; n = 20); claw length 17 µm (range: 14–19; n = 20). Hind tarsus length 41 µm (range: 39–44; n = 20); claw length 17 µm (range: 14–20; n = 18).

Thoracic tergite I ( Fig. 10 View FIGURES 10 – 13 ) with two pairs of setae (ratio of setae 1: 2 = 2.77:1; range 2.18‒4.00; n = 16) ( Table 1 View TABLE 1 ). Thoracic tergites II and III ( Fig. 10 View FIGURES 10 – 13 ) each with two pairs of anterior setae ( A2, A4); setae P1a and P2a very short; seta P2a nearer to P3 than to P2. Seta P5 very short. Length ratio of setae P1: P2 on mesonotum as 1:1.31 (range 1.15–1.43, n = 18). Tergites I–V each with three pairs of anterior setae ( A1, A2, A5); tergites II‒V lacking setae P1a and P3a. Seta A4 present on tergites VI‒VII. Seta P3 on urotergites II‒VI anterior to line P2‒P4 ( Fig. 11 View FIGURES 10 – 13 ). Tergite VIII ( Fig. 12 View FIGURES 10 – 13 ) with 3 pairs of anterior setae ( A2, A4, A5); P1a absent. Tergites IX and X with 12 setae; tergites XI and XII with 6 and 9 setae, respectively ( Fig. 10 View FIGURES 10 – 13 , Table 1 View TABLE 1 ). Prosternum ( Fig. 14 View FIGURES 14 – 22 ) formula 4 + 4 / 6, mesosternum and metasternum ( Fig. 15 View FIGURES 14 – 22 ) formulae typically 5 + 2 / 4 and 7 + 2 /4, respectively. Sternites I–VII with 3 anterior setae ( Figs. 16‒17 View FIGURES 14 – 22 ); sternites VIII‒X with 4 setae; sternites XI and XII with 6 setae ( Fig. 18 View FIGURES 14 – 22 ).

Thoracic tergites II and III ( Table 2 View TABLE 2 ) with sl pores; al pores on mesonotum. Tergites I‒VIII with psm pores, on tergite VIII opening between two small pointed teeth; al pores on tergites II‒VII; psl pores on tergites VI‒VII ( Fig. 11 View FIGURES 10 – 13 ). Tergite XII with ac pore (see Galli & Capurro, 2013, Fig. 12 View FIGURES 10 – 13 ). Thoracic sternites and abdominal sternites I‒II without pores. Sternite III with an asymmetrical spsm pore near the base of a seta P1a ( 10 adults); in four adults such pore is nearly medial, in three adults two symmetrical spsm pores present. Sternites IV‒VI with symmetrical spsm pore near the base of seta P1 ( Fig. 16 View FIGURES 14 – 22 ); spm pore far from posterior margin on sternite VII ( Fig. 17 View FIGURES 14 – 22 ); sternite XII with sal pores (see Shrubovych, 2014— Fig. 18 View FIGURES 14 – 22 ).

Imago and Pre-imago Maturus Junior Larva II

Formula Complementary Setae Formula Complementary Setae

Dorsal

Connecting lines on anterolateral corners of sternites IV–VI absent. Pleural pectines weakly developed ( Fig. 19 View FIGURES 14 – 22 ). Abdominal appendages II and III with long subapical seta and two setae, one lateral-apical and the other median-apical; comb VIII with 8–9 long teeth ( Fig. 13 View FIGURES 10 – 13 ). Penis with 6 + 6 setae ( Fig. 20 View FIGURES 14 – 22 ). Female squama genitalis with three spines on each acrostylus ( Figs. 21‒22 View FIGURES 14 – 22 ).

Chaetotaxic variation infrequent; asymmetrical shift of seta P1 towards P2 on abdominal tergite I (one adult); symmetrical absence of seta A4 on tergite VI (one maturus junior); symmetrical absence of seta A1 on tergite VII (one maturus junior); presence of seta Ac rather than setae A1 (formula 7/16) on tergite VII (one adult); symmetrical absence of seta A4 on tergite VI (one maturus junior); absence of seta Pc (formula 3/4) on sternite III (two adults – this arrangement may be the chaetotaxy of the holotype – see Rusek & Stumpp 1988); presence of seta Ac rather than setae A1 (formula 3/2) on sternite VIII (one adult); sternite XI with only two setae (one maturus junior).

Pre-imago. Length of body 967 µm (range 797‒1130; n = 4), head 113 µm (range 105‒121; n = 4), foretarsus length 75 µm (range 70‒79; n = 4), TR = 3.0–4.1, BS = 0.34–0.43. Chaetotaxy (Table III) identical to that of adults.

Maturus junior. Length of body 973 ± 123 µm (range: 787–1121; n = 12), head 114 ± 11 µm (range: 98–138; n = 11), foretarsus length 73 ± 6 µm (range: 63–88; n = 12), TR = 3.5‒4.2, BS = 0.23‒0.55. Chaetotaxy (Table III) differing from that of adults in presence of seta Pc instead of setae P1 on tergite VIII.

Larva II. Two specimens: length of body 800 µm, head 91 and 98 µm, foretarsus length 58 µm, TR = 3.4. Chaetotaxy is shown in Table III.

Distribution. Southern Italy: previously known only from the type locality in Apulia (a beech forest on N slope in Bosco Sfilzi, 10 km south of Vico del Gargano, Foggia province). The new material (see above) was collected in another locality of Foggia province ( Apulia) and in Basilicata.

Diagnosis and discussion. Due to the long foretarsal sensillum a and to sensilla b and c having the same length, A. apuliacus belongs to the confinis group of Acerentulus . A key to the species of this group can be found in Shrubovych et al. (2012). Rusek & Stumpp (1988) considered A. apuliacus to be related to A. exiguus Condé, 1944 , differing from it in the presence of seta A1 on tergite VII, thickened foretarsal sensillum a (slender in A. exiguus ), equal lengths of sensilla b and c (the former being shorter in A. exiguus ) and the number of spines on the acrostyli (three in A. apuliacus and two in A. exiguus ).

A more recently described species from France, Acerentulus charrieri Shrubovych, Schneider & D’Haese, 2012 , is close to A. apuliacus . Both species have 8 anterior and 16 posterior setae on Tergite VIII (including seta P1a and lacking P3a) and they share a similar general morphology of foretarsus (position and relative sizes of sensilla). Acerentulus charrieri differs from A. apuliacus in having a significantly longer foretarsus (125‒130 µm), slender foretarsal sensilla a and a’, sensillum b longer than c and distal position of seta δ4.