Trionymus jonesi, Williams, D. J., 2004

Williams, D. J., 2004, Two new mealybug species from the Falkland Islands (Hemiptera, Sternorrhyncha, Coccoidea, Pseudococcidae), Zootaxa 659, pp. 1-8 : 5-8

Trionymus jonesi sp. nov.

(Fig. 2)

Description

Body of adult female on microscope slide membranous, broadly oval, widest at about metathorax; 1.30–1.60 mm long, 0.85–1.15 mm wide. Anal lobes poorly developed, ventral surface of each lobe bearing an apical seta 100–115 µm long. Antennae each 180­200 m long, with 6 segments. Legs well developed, small for size of body; hind trochanter + femur 120–150 m long, hind tibia + tarsus 110–130 m long; claws stout and curved, each about 20 m long, bearing a pair of knobbed digitules, each noticeably longer than claw. All legs with short setae, except for conspicuously long distal trochanteral setae, each about 60 µm long. Ratio of lengths of hind tibia + tarsus to hind trochanter + femur 0.86–0.91. Ratio of lengths of hind tibia to tarsus 1.75–2.25. Translucent pores on anterior surface of hind coxa in most specimens, but a few specimens with translucent pores on both surfaces: one specimen with translucent pores also on posterior surfaces of hind femur and tibia. Labium about 70 m long, a little shorter than clypeolabral shield. Circulus absent. Ostioles present, poorly developed; posterior pair each with 0–2 trilocular pores on each lip, anterior pair of ostioles represented by mere slits, barely perceptible. Anal ring bearing 6 setae, each 105–115 m long, and 2 rows of cells, all situated on a wide rim. Cerarii numbering at most 3 pairs. Anal lobe cerarii each containing a pair of conical setae, each about 15 µm long and 5 µm wide at base, a single auxiliary seta and a cluster of trilocular pores, all situated on a membranous area. Penultimate cerarii (C17) each consisting of a pair of conical setae and a group of trilocular pores. Cerarii on abdominal segment VI (C16) each with at most a single conical setae and a group of trilocular pores.

Dorsal surface of body with short stiff setae, the majority each about 5 µm long, present mainly across middle of segments, but absent from submarginal areas: wide intersegmental areas also devoid of setae; longer setae, each 12.5–15.0 µm long, present across posterior abdominal segments but leaving a bare area above anal ring. Multilocular disc pores absent. Trilocular pores, each with thick rim, distributed in areas occupied by setae; noticeable concentrations on anal lobes, extending to submarginal areas; present also on marginal areas of abdominal segments VI and VII and extending to submarginal areas; elsewhere fairly sparse. Discoidal pores absent. Oral collar tubular ducts absent.

Ventral surface with short setae, similar to short setae on dorsum, sparsely distributed, leaving many bare areas; cisanal and obanal setae each about 25 µm long. Multilocular disc pores, each about 7.5 µm in diameter, present on posterior segments of abdomen only, fairly widely spaced in single rows across posterior edges of abdominal segments VI and VII; reaching lateral margins; a few also on posterior edge of abdominal segment V, at anterior edge of abdominal segment VI and in area posterior to vulva: total numbers of multilocular disc pores varying from 40–100. Trilocular pores sparsely distributed near setae. Discoidal pores absent. Oral collar tubular ducts, each about as long as a multilocular disc pore and narrower than a trilocular pore, few, 1 or 2 present medially on abdominal segment IV and occurring in single rows across middle of abdominal segments VI–VIII, to margins.

Material examined.

HOLOTYPE adult Ψ, Falkland Islands, East Falkland, Cusby’s Hill, on roots of Bolax gummifera (Apiaceae) , extracted by Tullgren funnel apparatus, 7.xi.2002 (A.G. Jones) ( BNMH).

PARATYPES, Falkland Islands, same data as holotype, 1 adult Ψ, 2 3rd­instar ΨΨ (on same slide as holotype) ( BMNH); Mt Usborne, on roots of B. gummifera , 7.ii.2004 (A.G. Jones), 6 adult ΨΨ, 2 3rd­instar ?? ( BMNH), 1 adult Ψ ( USNM).

Etymology

The species is named after Alexander G. Jones, University of Wales, Bangor, who collected all the specimens discussed in this work during expeditions for Falklands Conservation and made them available for study.

Comments

There are no close relatives of Trionymus jonesi in the New World, although the mealybug resembles some species presently included in Chnaurococcus Ferris. T. jonesi , however, is not congeneric with the type species C. villosus (Ehrhorn) , a North American species, which possesses dorsal oral collar tubular ducts, each with a deep collar. In lacking a circulus, dorsal oral collar tubular ducts, and dorsal multilocular disc pores, T. jonesi bears a superficial resemblance to Dysmicoccus junceus (McConnell) , a North American species formerly included in the genus Trionymus Berg. However , D. junceus possesses 6 pairs of cerarii and was transferred to Dysmicoccus by McKenzie (1967). The new species is included in Trionymus , a genus differing from Dysmicoccus in possessing fewer than 6 pairs of cerarii. Among the species in the New World currently placed in Trionymus , T. jonesi comes closest to T. coroneus Miller & McKenzie (described from Mexico) in lacking a circulus, dorsal multilocular disc pores, and dorsal oral collar tubular ducts. T. coroneus , however, possesses a single pair of cerarii only, and oral collar tubular ducts on the venter are present at least as far forward as abdominal segment III; in T. jonesi there are 3 pairs of cerarii at most and the ventral oral collar tubular ducts are much fewer and present mainly on abdominal segments V­VII, with only an occasional duct occurring on abdominal segment IV. T. danthoniae Morrison , known from Campbell Island on grass roots, differs from T. jonesi in possessing 1 or 2 circuli, and apparently multilocular disc pores present on the venter as far forward as the labium.

Among the African species of Trionymus , T. jonesi closely resembles T. pygmaeus De Lotto and T. rhizophilus De Lotto. However , T. pygmaeus , possesses 5 pairs of cerarii and the antennae are 7­segmented, whereas T. rhizophilus , although possessing 2 pairs of cerarii, also has dorsal oral collar tubular ducts that are lacking in T. jonesi . Besides, the antennae in T. rhizophilus are each 8­segmented, whereas in T. jonesi the antennae are each 6­segmented. It seems best to retain the new species in Trionymus , although the species has unusual characters. The concentration of thick­rimmed trilocular pores on the dorsal posterior segments is particularly striking. The genus Trionymus normally includes species that feed on grasses, although exceptions are known.