Oacoccus, Williams, 2007

Williams, D. J., 2007, Scale insects of the families Asterolecaniidae and Eriococcidae (Hemiptera: Coccoidea) in New Caledonia, Journal of Natural History 41 (21 - 24), pp. 1343-1366 : 1347-1348

Oacoccus gen. nov.

Type species. Oacoccus nothofagi sp. nov.

Description

Body of adult female on microscope slide, membranous, with cleft at posterior end of abdomen forming two apparent anal lobes. Base of cleft on dorsum with oval sclerotized area or plate, entire, except divided posteriorly by narrow cleft with parallel sides, forming anal lobes, each with an apical seta; base of cleft with cellular anal ring divided into two lateral sclerotized areas, containing six setae. Dorsal margin of body with an uninterrupted series of sclerotized finger-like extensions directed medially, each expanded at base at body margin, space between each base with an elongate microduct opening at margin. Antennae six-segmented, only gently tapering. Legs well developed, mesothoracic and metathoracic legs displaced posteriorly. Spiracles normal, metathoracic spiracles displaced nearer posterior end of body. Ventral segmentation apparent on abdomen, with oblique rows of quinquelocular pores directed forwards to metathoracic spiracles.

First-instar nymphs

None available after parturition, described from embryos only. Body oval, membranous, with dorsal marginal finger-like extensions and microducts as in adult female. Anal lobes poorly developed, rounded, each with apical seta. Anal ring U-shaped. Dorsum with series of submarginal and submedial slender setae. Quinquelocular pores present on venter in oblique rows extending forwards to metathoracic spiracles. Antennae six-segmented. Legs normal, claws slender, apparently without denticles.

Comments

Normally, genera assigned to the family Asterolecaniidae , based on characters of the adult female, as in Asterolecanium Targioni Tozzetti ( Russell, 1941) , Frenchia Maskell ( Lambdin and Kosztarab, 1981) , and Polea Green ( Lambdin, 1977) , possess 8-shaped pores, quinquelocular pores somewhere on the body, and other characters discussed above. Firstinstar nymphs usually have 8-shaped pores, occasionally three narrow sclerotized areas in the anal areas and claws that lack denticles ( Miller 1991). In the new genus, there are no 8- shaped pores in the adult female, the tubular ducts are very slender and straight, resembling long microducts, the antennae are six-segmented, there is an anal cleft with a large, entire dorsal anal plate or sclerotized area that is divided at the posterior end, and legs are present. First instar-nymphs of Oacoccus lack 8-shaped pores and the claws apparently lack denticles.

It could be argued that Oacoccus should be included in the family Eriococcidae . Firstinstar nymphs of Eriococcidae , however, usually possess enlarged setae, protruding anal lobes and denticles on the claws. Many adult females of Eriococcidae have protruding anal lobes but sometimes, as in Eriochiton Maskell ( Hodgson and Henderson, 1996) , Neoeriochiton ( Hodgson, 1994) , and Chilechiton ( Hodgson and Miller, 2002) , the lobes are displaced anteriorly forming a cleft at the posterior end of the body but the lobes always remain separate and never form a single plate-like area. There are genera presently included in the family Eriococcidae , such as the Australian genus Floracoccus Beardsley, 1974 , with few characters that allow easy assignment to any family. Floracoccus lacks anal lobes, enlarged setae and tubular ducts, the antennae and legs are reduced to tubercles, and quinquelocular pores are present. The genus, nevertheless, seems to be closely related to Sphaerococcopsis Cockerell , another Australian genus with clearer eriococcid features.

The anal ring of Oacoccus is similar to that of many species in the Asterolecaniidae with two plate-like areas joined anteriorly by a narrow rim. Furthermore, the claws in both the adult female and first-instar nymph lack denticles, and the labium, which appears to be two-segmented but with setae at the apex only, are asterolecaniid-like and it is for these reasons that the genus is tentatively assigned to the family Asterolecaniidae although reluctantly as a monotypic genus. There seems to be no other family at present that could contain it. The plate-like anal area of the adult female does not correspond to any discussed by Hodgson (1995) but the anal area of the first-instar nymph is more asterolecaniid-like.

When Ferris (1955) described the genus Mycococcus Ferris (type species M. copernicae Ferris ) from Cuba, he included the Australian species Sphaerococcus diaspidiformis Green in it as Mycocococus diaspidiformis (Green) and assigned Mycococcus to the family Asterolecaniidae . M. diaspidiformis is not congeneric with the type species but, as discussed by Miller et al. (1998), it should probably remain in the family Asterolecaniidae . Firstinstar nymphs of M. diaspidiformis lack 8-shaped pores, the adult female possesses tuberclelike antennae, and a labium that is two-segmented. Although M. diaspidiformis cannot be included in Oacoccus , there are similarities.

The two Australian genera Callococcus Ferris and Eremococcus Ferris , formerly placed in the family Asterolecaniidae , have been transferred to the family Eriococcidae by Gullan et al. (2005). These genera bear no resemblance to Oacoccus .

Etymology

The name is formed from the Greek word ‘‘ oa ’’, meaning a border in the form of a hem, alluding to the dorsal margin, combined with the generic name Coccus .