Macrocheles lundae Krantz

Halliday, R. B., 2005, Predatory mites from crops and pastures in South Africa: potential natural enemies of redlegged earth mite Halotydeus destructor (Acari: Penthaleidae), Zootaxa 1079, pp. 11-64 : 37-40

Macrocheles lundae Krantz

Macrocheles lundae Krantz, 1970: 19 .

Specimens examined: Site 94­32, 1 female.

Macrocheles lundae Krantz was described from a collection from Kleinmond, South Africa ( Krantz, 1970), very close to the present collection from Stellenbosch. The types were collected on a scarabaeid beetle, so it may be that this species is normally associated with dung or some other transient habitat in which such beetles occur. A search of almost 500 specimens of Macrocheles associated with South African dung beetles failed to reveal any further specimens of this species (specimens in ANIC). It is obviously not an abundant species in crops and pastures, and is not likely to have any impact on populations of H. destructor .

Macrocheles propinquus sp. nov. ( Figs 21 –28)

Specimens examined

Holotype female, Plettenberg Bay, roadside picnic area, 18.viii.1994, T. K. Qin, clover, grass, capeweed, site 30­13 (= 94­13). Paratypes, 3 females, 2 males, same data as holotype.

Description

Female

Dorsal idiosoma ( Fig. 21 ). Dorsal shield 794–823 µm long, 483–512 µm wide (n=4), with polygonal ornamentation throughout, weakest centrally, strongly developed posterior to setae Z4; with 28 pairs of setae and 22 pairs of pores; j1 adjacent, heavily pilose distally; j4, z4, J5, Z5, S5 lightly pilose distally; others smooth and pointed.

Ventral idiosoma ( Fig. 22 ). Tritosternum with rectangular base and strongly pilose laciniae. Sternal shield strongly ornamented; with a wavy line of punctations joining setae st2, punctate lines in anterior half of shield, and a band of heavy punctation in posterior half; shield with three pairs of smooth pointed setae and two pairs of lyriform pores. Epigynial shield semicircular, with curved lines of punctations and a pair of smooth pointed setae; flanked by and partly covering a pair of elongate paragynial plates; metasternal plates small, oval, each with a smooth pointed posterior seta and an anterior pore. Ventri­anal shield with concentric curved lines of punctations in anterior half, punctate polygonal ornamentation in posterior half, with three pairs of smooth pointed ventri­anal setae, a pair of smooth para­anal setae, and a short, smooth post­anal seta; cribrum very narrow, not reaching post­anal seta. Unsclerotised opisthogastric integument with a pair of narrow elongate metapodal plates and ca. 7 pairs of setae, each inserted in a minute platelet.

Gnathosoma . Epistome with a long bifurcate median process, spiculate basally, triangular lateral processes, and serrated lateral margins ( Fig. 23 ). Fixed digit of chelicera with a heavy ridged triangular tooth and a terminal hook; dorsal seta heavy, erect, pilus dentilis long, fine. Movable digit with a bidentate proximal tooth, a small triangular distal tooth, and a terminal hook; arthrodial brush long, more than half length of movable digit ( Fig. 24 ). Hypostomal groove with 5 rows of denticles, each with ca. 15 denticles, a smooth transverse groove, and an M­shaped anterior row of denticles. Anterior hypostomal setae (h1) and internal posterior hypostomal setae (h3) long (ca. 65 µm), exterior posterior hypostomal (h2) and palp coxal setae shorter (ca. 30 µm); internal malae fine, curled ( Fig. 25 ). Palp chaetotaxy normal for genus, palp tarsal claw 3­tined.

Legs. Chaetotaxy: Leg I: coxa 0 0/1 0/1 0; trochanter 1 0/1 0/2 1; femur 2 3/1 2/3 2; genu 2 3/1 2/1 2; tibia 2 3/2 2/1 2; Leg II: coxa 0 0/1 0/1 0; trochanter 1 0/1 0/2 1; femur 2 3/1 2/2 1; genu 2 3/1 2/1 2; tibia 2 2/1 2/1 2; tarsus 3 3/2 3/2 3 + mv, md; Leg III: coxa 0 0/ 1 0/1 0; trochanter 1 1/1 0/1 1; femur 1 2/1 1/0 1; genu 1 2/1 2/0 1; tibia 1 1/1 2/1 1; tarsus 3 3/2 3/2 3 + mv, md; Leg IV: coxa 0 0/1 0/0 0; trochanter 1 1/2 0/1 0; femur 1 2/1 1/0 1; genu 1 2/1 2/0 0; tibia 1 1/1 2/1 1; tarsus 3 3/2 3/2 3 + mv, md. All setae fine, smooth, pointed, except for 5–6 setae on each of tarsi II–IV, which are thickened and spine­like, and ventral setae on tibia and basi­femur IV, which have slight distal pilosity. Pre­tarsi II– IV with opercula shorter than claws, with short distal bifurcation, lateral lobes of pulvillus similar in length to median lobe.

Male

Dorsal idiosoma. Dorsal shield 554–559 µm long, 349–353 µm wide (n=2); narrowed posteriorly, posterior margin dentate; chaetotaxy as for female except J2 displaced posteriorly between pores P12 and P14.

Ventral idiosoma. Sternal and genital shields fused to form a sterniti­genital shield with five pairs of smooth pointed setae and four pairs of pores, shield expanded laterally to capture an additional two pairs of opisthogastric setae, shield with uniform punctate ornamentation throughout; ventri­anal shield with 3 pairs of ventri­anal setae, pair of paraanal setae and post­anal seta, all smooth and pointed, shield with uniform punctate ornamentation throughout.

Gnathosoma . Fixed digit of chelicera with three small triangular distal teeth, a robust medial tooth and a terminal hook, dorsal seta conspicuous; movable digit with one medial tooth and a terminal hook; spermatodactyl sinuous, tapering to a fine distal point ( Fig. 26 ). Other features of gnathosoma as for female.

Legs. As for female, except ventral surface of femur II with a heavy thumb­like spur, seta av on genu and tibia II represented by short blunt protrusions ( Fig 27 ); femur IV with a large postero­lateral thumb­like spur and a ventral spur bearing a thickened spine­like seta ( Fig 28 ).

Notes

At least 30 described species of Macrocheles have been recognised in southern Africa ( Ryke & Meyer, 1958; Ryke, 1959, 1964; Evans & Hyatt, 1963; Krantz, 1970, 1981; Van Driel, 1973, excluding the species described by Van Driel, 1973, whose names are not available). M. propinquus may be distinguished from all of these by the distinctive pattern of sternal shield ornamentation in the female.

M. propinquus is a member of the Macrocheles muscaedomesticae (Scopoli) species group, which prey on insect eggs and larvae wherever there is decaying organic matter, especially dung ( Halliday, 1990). The characteristic features of this group are the pattern of ornamentation on the sternal shield of the female; specifically, a transverse punctate line joining the bases of the second pair of sternal setae, a pair of punctate lines passing through the first sternal pores and running obliquely back towards the centre of the shield, and a band of strongly developed irregular ornamentation across the full width of the posterior half of the shield. The female of M. propinquus is strikingly similar to that of M. muscaedomesticae . The females of these two species may be distinguished by dorsal shield setae r2, r3, r5, which are smooth and pointed in M. propinquus , distally pilose in M. muscaedomesticae . Also the sterniti­genital shield and ventri­anal shields of the male are fused in M. muscaedomesticae , separate in M. propinquus .

The fact that this species was represented by only 6 specimens from a single locality, and that at a picnic area, suggests a biology similar to that of Macrocheles muscaedomesticae , which often occurs in human­produced rubbish deposits. The single locality at which it has been collected is outside the geographic distribution of H. destructor . This species has not been recorded in Australia, but is unlikely to be a useful predator of H. destructor .

Etymology

The name of this species alludes to its close similarity to M. muscaedomesticae .

Figures

FIGURES 21 – 25. Macrocheles propinquus sp. nov., female. 21. dorsal idiosoma; 22. ventral idiosoma; 23 epistome; 24. chelicera; 25. hypostome. Scale bar = 100 µm for 21, 22, 50 µm for 23, 24, 25.

FIGURES 26 – 28. Macrocheles propinquus sp. nov., male. 26. chelicera; 27. tibia, genu and femur of leg II; 28. trochanter, femur and genu of leg IV. Scale bar = 100 µm for 27, 28, 80 µm for 26.