Icerya imperatae Rao

Hodgson, Chris J. & Łagowska, Bozena, 2011, New scale insect (Hemiptera: Sternorrhyncha: Coccoidea) records from Fiji: three new species, records of several new invasive species and an updated checklist of Coccoidea, Zootaxa 2766, pp. 1-29 : 2-5

Icerya imperatae Rao

Icerya imperatae Rao, 1951: 58 .

Icerya imperatae Rao was described off Saccharum spontaneum (Poaceae) from Ada Tanoa Sagay, Negros Occidental, Philippines, in 1951. The species was not recorded again until 2004, when it was discovered damaging grasses on Babeldaob, in the Republic of Palau ( Williams et al., 2006), where it had been first detected in 2004 infecting imported grass ( Brachiaria decumbens ) planted to control erosion along the margins of a new road. Initially, the damage consisted of chlorotic patches and transverse bands on the infested leaves but, by July 2005, large patches of the grass had died and it was being replaced on the road verges by an invasive introduced legume ( Stylosanthes erecta (Fabaceae) ( Williams et al., 2006).

As part of their study to identify the species in Palau, Williams et al. (2006) examined specimens of Icerya off grasses in a number of Institutions and found that, in fact, I. imperatae was quite widespread. They recorded it from various Poaceae from Australia ( Oryza sativa , sorghum , Paspalum notatum and other grasses), Brunei (off grass), Malaysia ( Paspalum conjugatum & Ottachloa nodosa ), Palau ( Brachiaria decumbens , Chloris barbata , Ischaemum sp., Pennisetum sp., Imperata conferta & Bothriochloa sp.) and the Philippines ( Saccharum spontaneum , Imperata exultata , sugarcane & Bambusa spinosa ). Here we record Icerya imperatae from Fiji for the first time, off Paspalum sp. Williams had intended to redescribe the species but has been unable to and therefore we are taking the opportunity to do so here.

Adult female ( Fig. 1 )

Material examined. Palau Is., Babeldoab (Babeldaup on slide), on introduced grass Brachiaria decumbens , 12.x.2004, A. Moore A033 ( BMNH): 1/2adff (good). Fiji, Viti Levu, Suva, on Paspalum sp. near shore, 12.vii.2009, C.J. Hodgson ( BMNH): 1/1adf; as previous but from Thurston Gardens, 12.vii.2009, Paspalum sp., C.J. Hodgson #75 ( BMNH): 3/3adff (1 good, 2 poor); Viti Levu, Savura Nature Reserve, on grass sp., 15.vii.2009, C.J. Hodgson ( BMNH): 2/3adff (1 good, 1 poor, 1 pharate adult); also Viti Levu, Sigatoka Dunes, on grass, 27.vii.2009, C.J. Hodgson #135 ( BMNH): 1/1adf (good).

Unmounted material. “Conspicuous and fairly large, often attaining a length of 7 mm when adult. The body .. is reddish orange in life, its legs .. black and its dorsal surface is covered with white wax which also projects as short, thick filaments at the posterior end. A white wax ovisac is produced ventrally from a band of cuticular pores on the anterior abdomen. Eggs are laid into the ovisac and the first-instar nymphs (crawlers) develop protected by the female’s body above and the wax of the ovisac below. The ovisac does not protrude far beyond the end of the abdomen in I. imperatae , unlike the prominent, often fluted, ovisac of many other Icerya species.” ( Williams et al., 2006).

Mounted material. Elongate oval, covered in setae of varying lengths and thicknesses, longest mainly around margin. Legs and eyes blackish. Body length 3.0– 5.5 mm long, width 1.6–3.5 mm.

Dorsum. Dorsal setae fairly evenly distributed over surface, perhaps more obviously in segmental bands on abdomen; very variable in length, longest near margin, where each up to about 180–250 μm long (with some up to about 350 μm long), with a collar-like basal socket about 15 μm wide; most dorsal setae 80–150 μm long, each with a less pronounced collar to basal sockets; smallest setae 20–25 μm long, basal socket without a collar. Dorsal pores about as abundant as dorsal setae but apparently slightly more abundant in anal area, each mainly slightly oval and about 10 μm widest (but some rather more round in anal area); most pores with an oval centre (sometimes divided medially) with an outer ring of mainly 8 (range 7–9) loculi. Dorsum also with some very small sclerotised pores, rather variable in frequency, each about 2.5 μm wide. With a pair of abdominal spiracles on abdominal segments VIII, VII and VI, each sclerotised outer opening about 20 μm wide, main part of spiracle about 25 μm long, and with a tube-like extension about 40 μm long, ending in narrow trachea. Anus membranous but with inner tube ending in an oval to round sclerotised ring; anal ring about 80–100 μm widest; inner part on good Fiji specimen with a faintly reticulated membrane.

Venter. Setae similar to those on dorsum but less frequent, particularly within ovisac band; those around vulva quite short with a very broad basal socket. Ventral pores mainly similar to those on dorsum but tending to be smaller with fewer loculi in outer ring (range 4–7 but mainly with 6 loculi); most pores 8–10 μm widest but smallest only 7 μm widest; rather more abundant near each thoracic spiracle, also around vulva, where pores rounder with more loculi (mainly 8 but up to 10); with a distinct ovisac pore band anteriorly on abdomen forming a complete arc from between metacoxae to about abdominal segment IV or V, where it narrows and fades out; band about 6–8 pores wide anteriorly but becoming narrower and less distinct posterolaterally; pores in ovisac band tending to be mainly oval, with 7–10 or even 11 outer loculi, largest 10 μm wide. Small, sclerotised pores, similar to those on dorsum, present throughout but perhaps less frequent than on dorsum. Cicatrice: a single oval, cicatrice, about 185 μm wide and 75 μm long, present medially posterior to vulva on one specimen from Palau but absent from all other specimens.

Antennae mainly 7 segmented but third segment partially divided on all specimens studied; each segment with a whorl of long setae; apical segment subequal in length to 3rd segment; apical segment with 3 fleshy setae; total length 615–750 μm. Eyes each on top of a sclerotised convexity, present immediately posterior to base of each antenna; sclerotised area 95–112 μm widest, each lens about 35–40 μm. Clypeolabral shield well developed, 380– 420 μm long; labium probably 3 segmented, with a group of perhaps 7 pairs of setae on segment I, 2 pairs on segment II and unknown on segment III. Thoracic spiracles: width of anterior peritremes 90–112 μm, posterior peritremes 90–130 μm. Legs well developed and dark, each with a large apodeme; metathoracic leg lengths (μm): coxa 330–420; trochanter + femur 570–640, each trochanter with 4 small campaniform pores in a line on each surface, and each with a long seta ventrally; tibia 505–635; tarsus 300–340, each with a campaniform pore on dorsal surface proximally; tarsal digitules setose and quite short; claws 60–75, each with about 5 very small denticles; claw digitules each capitate and much longer than claw. Vulva fairly distinct and membranous, with two membranous invaginations along posterior margin.

Comment. Williams et al. (2006) stated that there was some variation between the specimens that they had studied. In particular, they found that the hind tarsus was shortest in material from Palau and Malaysia (280–290 μm) and longest on specimens from the Philippines (350–420 μm). The material studied above was intermediate. In addition, the frequency of the very small sclerotised pores also varied in the material we studied, with rather few on the specimens from Palau but frequent on the Fiji material. The above description differs from that of Rao (1951) in that: (i) the antennae of all specimens were 7 segmented, with the segment III partially divided whereas Rao’s specimens were clearly eight segmented (also described as 8 segmented by Unruh & Gullan, 2008); (ii) none of the setae were actually black when mounted; (iii) the cicatrice was present or absent; (iv) no pores with triangular centres were noted (but were recorded by Unruh & Gullan, 2008), and (v) some dorsal pores on the Fiji specimens had the central oval loculus clearly divided by a membrane. In their study on species in the tribe Iceryini, Unruh & Gullan (2008) also considered that the central loculus of some of pores was divided and therefore bilocular. Unruh & Gullan (2008) also describe the cicatrice as being round and the ovisac pore band as only being 3 or 4 pores wide anteriorly.

As this species was collected in four sites on Viti Levu, it would appear to be widespread. On two occasions it was collected near the shore, once from a forested area and once from the Botanical Gardens in Suva. As described by Williams et al. (2006), the leaf blade of the grass showed purplish blotches but otherwise seemed to be relatively unaffected. It is unclear whether it is a potential problem to other Poaceae on the island.

Figures

FIGURE 1. Adult female Icerya imperatae Rao. Where A = anterior dorsal loculate pore; B = area of dorsum showing density of pores and setae; C = sclerotised dorsal pore; D = dorsal setae; E = abdominal spiracle; F = posterior dorsal loculate pore; G = anal tube; H = ventral seta near vulva; J = vulva area; K = claw; L = area of derm within ovisac band showing density of pores and setae; M = ventral loculate pore; P = sclerotised ventral pore; Q = area of ventral derm showing density of pores and setae; R = trochanter of prothoracic leg; S = antenna; T = loculate pores in ovisac band, and X = loculate pore near anus and vulva.