Malaconothrus monodactylus

Malaconothrus monodactylus (Michael, 1888)

(Fig. 1)

Nothrus monodactylus Michael (1888), Hull (1915, 1916).

Malaconothrus egregius Evans (1952).

Malaconothrus gracilis van der Hammen, 1952 new synonymy.

Comparison of Michael's slide-mounted specimens of N. monodactylus from the British Museum and Dr van der Hammen's syntypes of M. gracilis reveal little justification for separating these species. The areolar patterning of Michael's specimens is fainter than that of most of the M. gracilis syntypes but this might arise from the less adequate clearing of Michael's mounts. The fragility of the cerotegument in most species of Malaconothrus also gives rise to a degree of apparent variation between some individuals.

The following notes derive from the study of Michael's slides labelled:

Nothrus monodactylus A. D. Michael 1930.8.25.1127

Nothrus monodactylus and underside. A.D. Michael 1930.8.25.1128

Dimensions. Michael (1888) gave the following dimensions: length 0 29 mm, breadth 019 mm. The first figure is in error since the mean dimensions of his slide-mounted specimens are: length 410 µm (N = 3), width at widest point 210 µm (N = 2).

Colour. Yellowish on slide.

Prodorsum. Rostrum rounded, rostral setae fine and smooth, just overtopping rostrum. Lamellar setae fine, smooth and long, but not reaching tip of rostrum. Distance between lamellar and inter-lamellar setae greater than distance between lamellar and rostral setae; lamellar setae not in direct alignment vertically with rostral setae. Inter-lamellar setae about half length of widest point of prodorsum. Exobothridial setae difficult to distinguish separately on any of Michael's specimens but appear tp be half the length of the inter-lamellar setae. Prodorsal surface finely punctate, areoles all smaller in size than those of notogaster, variable in size and closely packed.

Notogaster. Finely and densely punctate with a complete covering of regularly distributed areoles, each separated by a distance equivalent to its diameter. The sizes of the areoles vary little and each appears to bear its own coarser punctation. The sides of the hysterosoma are parallel, terminating in a squared-off projection. All notogastral setae are fine and smooth, their relative lengths and distributions are shown in Fig. 1A.

Venter. Epimeres coarsely punctate except medially. Length ratio of genital to anal plates 1:1-3. Fields lateral to ano-genital region with evenly scattered areoles, each about equivalent in size. All ventral setae fine and smooth.

Appendages. Typical for genus.

Distinguishing features. The species can be distinguished by the characteristically different forms of patterning on the prodorsum and on the notogaster.

New records. From litter and soil beneath pure and mixed stands of oak, alder, Scotspine and Norway spruce, Gisburn Forest, Lancashire (grid ref. SD 750588), coll. K. Chapman; from edge of a bog, Carnsore Point, Co. Wexford, Ireland, coll. G. Purvis.

Remarks. Malaconothrus egregius has not been recorded from the British Isles but has occasionally been confused with M. monodactylus (Evans 1952). Malaconothrus egregius can be distinguished from all other species by the following characteristics (gleaned from specimens confirmed as M. egregius and kindly loaned by Dr L. van der Hammen):

(1) Elongate diamond-shaped scales anteriorly and laterally on the notogaster.

(2) Prodorsum and notogaster finely punctate.

(3) Lamellar setae closer to rostral setae than to inter-lamellar setae.

(4) Setae d 1 closer together than setae c 1.

(5) Distal spines (ft") on tarsi I elongate.