Pariaconus gracilis (Crawford, 1918)

Percy, Diana M., 2017, Making the most of your host: the Metrosideros-feeding psyllids (Hemiptera, Psylloidea) of the Hawaiian Islands, ZooKeys 649, pp. 1-163 : 37-41

Pariaconus gracilis (Crawford, 1918) Figures 15, 16, 46 A–F

Kuwayama gracilis Crawford, 1918: 447.

Pariaconus gracilis (Crawford), Enderlein (1926): 401.

Adult colour.

General body colour typically dark brown to black throughout, but occasionally partly or entirely pale cream or yellow throughout (Fig. 15 Q–R). Head often darker than the rest of the body. Individuals are not distinctly bicoloured (e.g. without distinct dorsal stripe). Fore wing membrane clear, or slightly fuscous.

Adult structure.

Fore wing apex rounded; surface spinules densely distributed throughout all cells; short to minute setae on margins and veins (Fig. 15 A–F). Antennae short (av. length 0.54; ratio AL:HW av. 1.02); genal processes extremely short (ratio VL:GP av. 5.63); short to minute setae on vertex and thorax; distal proboscis segment short (av. length 0.07); hind tibia short relative to head width (ratio HW:HT av. 1.31) Fig. 15 G–P, S–U). Male terminalia (Fig. 16 A–H): paramere shorter than proctiger (ratio MP:PL av. 1.25), broad at the base and tapering only slightly towards the apex, sometimes slightly constricted medially, no apical hook but apex with bipartite sclerotization (Fig. 16G); distal aedeagus segment longer than paramere (ratio PL:AEL av. 0.88) with inflated base, apex hooked but flattened dorsally, hook apex blunt (ratio AEL:AELH av. 2.96). Female terminalia (Fig. 16 I–K): proctiger dorsal surface either straight, or with slight medial depression (Koolau), anal ring long (ratio FP:RL av. 2.44), apex bluntly acute; subgenital plate with slight or more pronounced medial bulge ventrally, apex bluntly acute; ovipositor apex with no or very reduced serrations above, two reduced serrations below, valvulae dorsalis not strongly convex dorsally.

Egg.

Unpigmented, elongate, slender, slightly sinusoidal, dorsal surface with widely spaced interrupted striations, medium-short pedicel positioned 1/4-1/3 length from base, tail long (Fig. 16L).

Immature.

Colour and structure: Orange or cream. 5th instar: Narrowly ovoid in outline with wing buds protruding and with distinct humeral lobes (Fig. 46A, D). Tarsi with small reduced claws (Fig. 46D). Circumanal ring shallowly v-shaped, with a single row of elongate cells (Fig. 46C, E). Chaetotaxy: 5th instar: Margin with medially expanded and overlapping diamond-shaped setae, dorsal surface rugose with ridges but otherwise only minute simple setae (Fig. 46 B–C). 1st instar (Fig. 46F): anterior margin of the head with long simple setae, otherwise marginal setae are narrow, blunt sectasetae (a single pair post ocular, a single pair on the apices of each wing bud, and the margin of the abdomen with approximately 9-10 pairs); by the 2nd instar, the characteristic diamond-shaped sectasetae are evident around the entire margin.

Host plant notes.

Predominantly on pubescent and tomentose morphotypes.

Island.

Oahu, Molokai, Maui.

Distribution notes.

A common species on Oahu. Four clusters can be recognized in the DNA analysis: (a) individuals from Molokai and Maui; these in turn group with (b) a population from Oahu’s southern Koolau Mnts that have more developed genal processes (Fig. 15G, I). Another cluster includes (c) individuals from both southern and northern Koolau Mnts with moderately reduced genal processes (Fig. 15J, L), and (d) a fourth cluster comprises all individuals from Mnt Kaala, Waianae Mnts, with much reduced genal processes. It appears that this Kaala population is ancestral with increasing development of genal processes being a derived characteristic in Koolau populations; Maui and Molokai specimens have moderately reduced genal processes and appear to be immigrants from the Koolau region of Oahu.

Biology.

The immatures are free-living, usually on the lower leaf surface of pubescent and tomentose morphotypes, this host morphotype preference is also noted on slide specimens collected in 1973 by Beardsley (BISH). Eggs appear to be laid mostly singly and sparsely distributed amongst the leaf trichomes.

Comments.

One of the most commonly encountered species in the bicoloratus group. Two forms are recognized (Figs 15-16): form gracilis (based on the type is the more common form, with short rounded genae) (Fig. 15J, L), and form conconus (has more developed, apically acute genae) (Fig. 15G, I). Both these forms can be found sympatrically in the Koolau Mountains (Oahu) and form distinct genetic clusters, suggesting some reproductive isolation.

Type material.

Holotype female (dry mounted, BPBM). See Table 2 for details of type and other material examined for this study.