Pentachaeta skusei, McAlpine, 2014

McAlpine, David K., 2014, Review of the Australian Genus Pentachaeta (Diptera: Heleomyzidae), with Descriptions of Nine New Species, Records of the Australian Museum 66 (5), pp. 247-264 : 257-258

Pentachaeta skusei n. sp.

Figs 26–29

Type material. Holotype ♂. Victoria: Belgrave, near Melbourne , [probably margin of Sherbrooke Forest, c. 37°53'S 145°22'E], 21.i.1966, D.K.M. ( AM K310595 ). Glued to card point, postabdomen in genitalia tube on same pin . Paratypes. Victoria: 2♂♂, Ninks Road, Kinglake , Jan 1980, B.W.B. ( ANIC) . New South Wales: 1♂, below Govett’s Leap, Blue Mountains , Dec. 1956, D.K.M. ( AM) .

Description (male)

Resembling P. edwardsi and related species without sexual dimorphism of tibiae; agreeing with description of that species, except as indicated below.

Coloration generally as for genus; details as given for P. edwardsi except as here noted. Fore femur orange-tawny, becoming brownish dorsally (perhaps faded in old type specimens); fore tarsus with segments 1 and 5 brown or largely brown, segments 2 to 4 pale tawny-yellow; mid tarsus tawny yellow, indistinctly brownish distally in faded specimens; hind tarsus dark brown.

Abdomen. Surstylus ( Fig. 26 ) ovate-lanceolate, distally gradually tapering to obtuse apex, outer surface extensively microtrichose, also with scattered short but rather stout setulae, which may be more numerous on posterior part of outer surface, apical part of inner surface with few setulae of variable size and marginal group of minute setiferous tubercles, at base of inner surface fascicle of short, stout setulae, either not arising from a common prominence, or on very slight prominence; subepandrial process ( Fig. 29 ) with numerous stout setulae towards apex and on inner surface; apex of gonostylus with three or four large setulae and sometimes few much smaller ones, with flat or slightly concave posterodistal densely pustulose zone; bulb of aedeagus without invaginated teeth; cercus ( Figs 27, 28 ) narrowly extended posteriorly, much broadened across base of anterior lobe, with pair of anterior lobes strongly divergent, at broadest part with prominent dorsal (and thus partly concealed) setulose tubercle ( Figs 27, 28 ), on exposed ventral surface with extensive armature of large setulae, becoming sparser and finer on anterior lobe.

Dimensions. Total length 3.2 mm; length of thorax, 1.3–1.6 mm; length of wing, 3.4–4.0 mm.

Distribution. New South Wales: Blue Mountains. Victoria: forested areas E and NE of Melbourne. Map references 4L, 7J ( Fig. 4 ).

Notes

Pentachaeta skusei belongs among those species without sexual dimorphism of the tibiae and with the fore tibia tawny yellow with brown apex. It differs from other such species in having segments 2 to 4 of the fore tarsus tawny yellow (dark brown in related species). The form of the surstylus ( Fig. 26 ) is distinctive, though somewhat resembling that of P. gilliesi , but the male cercus is very different (compare Figs 27 and 30 ). I suspect that the unknown female will be distinguishable from related species by the coloration of the fore tibia and tarsus, as in the male.

This species is dedicated to Frederick A. Skuse, the first Diptera specialist employed at the Australian Museum.

Figures

Figure 4. Reference map for distribution of Pentachaeta species in eastern Australia. Numbers in each rectangle (2° longitude by 2° latitude) are numbers of recorded species. Map references are given under Distribution for each species.

Figures 26–29. Pentachaeta skusei, male, Govett’s Leap (26) pair of surstyli, posteroventral view; setulae shown only on left surstylus and on prominence of inner basal surface of right surstylus (latter seen through transparency); scale = 0.2 mm. Pentachaeta skusei, Belgrave (27) epandrium with cerci, setulae shown only on left cercus and dorsal tubercles; scale = 0.2 mm; (28) medial view of anterior lobe of right cercus; scale = 0.1 mm. Pentachaeta skusei, Govett’s Leap (29) left gonostylus, subepandrial process and associated parts, lateral view; scale = 0.05 mm. as, articulating sclerite; dt, dorsal setulose tubercle of cercus; eh, sclerotized extension of hypandrium; g, gonostylus; pl, posterolateral extension of basiphallus; sp, subepandrial process.

Figures 30–33.Pentachaeta gilliesi, Mount Bonython (30) epandrium with cerci, showingright subepandrial process and basal prominence of right surstylus; scale = 0.2 mm; (31) pair of surstyli, posteroventral view; setulae shown only on left surstylus; scale = 0.2 mm; (32) apex of left surstylus, inner surface view; scale = 0.05 mm; (33) left gonostylus, lateral view; scale = 0.05 mm.