Swezeyana Caldwell, 1940

Percy, Diana M., 2018, Revision of the Hawaiian psyllid genus Swezeyana, with descriptions of seven new species (Hemiptera, Psylloidea, Triozidae), ZooKeys 758, pp. 75-113: 75

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Swezeyana Caldwell, 1940


Swezeyana Caldwell, 1940 

Swezeyana  Caldwell, 1940: 389. Type species: Swezeyana elongagena  Caldwell, 1940, by original designation.


Adult. General colour variable ranging from pale yellow-brown, to green or yellow-green, to almost black; often with pink or reddish highlights on the fore wing as well as on the body, especially genal processes, legs, and abdomen. Fore wing membrane either with distinct darker patches or clouds of pigmentation, these range from dark brown to red, and in some cases are limited to termination of veins at wing margins and around cross veins between Rs and wing margin, if without distinct patterns of pigmentation, appearing uniformly clear, opaque yellow or fuscous; wing veins pale to red or dark brown, cross veins between Rs and ventral wing margin with or without pigmentation. Adult length including fore wing from 2-5 mm. Fore wing elongate and usually narrow (ratio WL:WW > 2.80, often > 3), acute to bluntly acute apically, either with trifurcation of veins R, M and Cu1, or with vein R branching anterior of bifurcation of M and Cu1; vein Rs long, reaching wing margin distad of M fork, but either with or without complete extension of Rs to wing margin, incomplete termination of Rs usually marked by pigmentation; vein R shorter than Cu1 and terminating at base of Rs, a pseudopterostigma is present between base of Rs and wing margin, and a more or less thickened wing margin (C+Sc) is present from the wing base to the pseudopterostigma, in some cases occupying part or entire area of cell c+sc; with or without one or more partial or complete cross veins traversing cell r1 between vein Rs and ventral wing margin; a single, broadly shaped marginal cluster of radular spines (Figs 3O, 6J) in cells cu1, m1, and m2; surface spinules either present in all cells, dense or sparsely distributed, or few to absent from c+sc, r2 and r1, often relatively sparsely distributed but becoming denser towards wing margin. Hind wing narrow and elongate (> 0.5 length of fore wing), clear or slightly fuscous in basal half. Head moderately deflexed downwards, vertex more or less flat dorsally, with lateral ocelli lying on small tubercles, medial epicranial suture distinct; genal processes extremely long, often upturned at apices, with scattered long setae and usually a single, long subapical seta on each process. Antennae short; antennal segments 10, either entirely dark, or more usually with terminal 3(-7) segments darker, or distal part of segments 3-8 darker; a single rhinarium apically on each of segments 4, 6, 8, 9; 1-2 long setae on each of segments 3-9, terminal segment with two unequal length apical setae. Distal proboscis segment short, darker apically. Thorax somewhat flattened to only moderately arched; vertex and thorax with scattered short to moderately long setae. Legs short, hind legs robust with femur longer than tibia; hind leg with meracanthus reduced to almost absent; metafemur with several stout setae apically; metatibia with or without distinct genual spine basally and typically with 1+2 (occasionally 1+3) sclerotized apical spurs; pro- and mesotarsi subequal in length, metatarsi unequal with extremely long basal tarsus slightly expanded with concave, ridged underside (Fig. 3M). Male terminalia with somewhat elongate subgenital plate; proctiger with pronounced posterior lobes medially, 1-2 long setae usually present on posterior apices of each lobe, length shorter, subequal or longer than paramere; paramere shape variable, generally broad basally and tapering to apex, with two stout setae on the interior apex (sometimes appearing as one from lateral view); distal aedeagus segment apex hooked. Female terminalia with medium to long dorsal and ventral setae; proctiger either truncate and markedly convex apically, with apex broad, blunt, bearing small medial cleft and fringed with stout setae, or dorsal surface more or less straight, apex tapering, lacking medial cleft and distinct fringe of setae; proctiger longer than subgenital plate; anal ring hour-glass shaped (with or without a head compartment at proximal end) and composed of a, usually, uninterrupted, double row of cells, posterior/distal portion of ring margin either smooth or convoluted; subgenital plate ventral surface either convex or more or less straight, apex terminating in a variably shaped beak often bearing a short or more pronounced medial cleft spanned by a short or extended membrane; ovipositor valves small, without serrations (Fig. 9O).

Egg. Known for four species. Pale or light brown, oblong-ovoid with a short, laterally positioned pedicel sub-basally on underside; distinctly hexagonal, honeycomb-like, sculpturing, to semi-hexagonal or rounded indentations dorsally; underside unsculptured, tail apparently lacking.

Immature. Known for four species. 5th instar oblong-ovoid, ventro-dorsally flattened with slightly protruding wing buds and distinct humeral lobes; antennae with 3(-4) segments bearing 3(-4) rhinaria (1 on segments 2-3, and 2 on apical segment) and two long, terminal, simple setae of unequal length; tarsi with broad crescent arolia and extremely small, reduced claws; each terminal tarsus bearing a long capitate seta; anus situated ventrally, circumanal ring broad and composed of a single row of elongate cells; dorsum either with wax producing pores (see Tuthill 1966), or non-wax producing tubercles and tentacles (Fig. 12). Chaetotaxy: 5th instar with either continuous or interrupted coverage of marginal setae; overall setal types, even between closely related species (e.g., S. reticulata  and S. tentaculata  ), highly variable (Fig. 12). Smaller instars only known for S. reticulata  and S. tentaculata  , in which tubercles are apparent from 2nd instar (Fig. 13).


All species for which the biology is known have free-living immatures on the surface of leaves (either lower, or both upper and lower surfaces). Those species with immatures described here with protruding tubercles and tentacles were mostly found on the lower leaf surface among dense indumentum and often close to the mid-rib (Fig. 12N).

Host plant.

All Swezeyana  are host specific on a single Hawaiian endemic host plant species, Planchonella sandwicensis  ( Sapotaceae  ).


Two species groups are recognized, elongagena  group and reticulata  group, based primarily on the strikingly different forms of female terminalia. The elongagena  group has broad, truncate female terminalia with a strongly convex proctiger apex; the proctiger and subgenital plate bear a small to pronounced medial cleft at the apex. In contrast, the reticulata  group has tapering terminalia without a medial cleft in the proctiger apex. In both species groups the subgenital plate terminates in a more or less well developed beak with small to pronounced cleft spanned by a membrane. The underlying endoskeleton of the two different forms of female terminalia indicate distinctly different development of the apodemes in the two species groups: broad and short in elongagena  group (Fig. 4P), and long and narrow in reticulata  group (Fig. 10I). However, not all species treated here are known for both sexes, therefore current assignment to these groups relies on other characteristics and DNA barcode data (see Discussion). Due to the unknown female morphology and inconclusive placement in the molecular phylogeny, S. magnaccai  is not placed within a species group. Fore wing characteristics such as wing membrane colouration and pseudoveins/cross veins are found in both groups. The 5th instar immatures may also be diagnostic, with elongagena  group having wax producing pores dorsally (illustrated in Tuthill 1966 for S. elongagena  ) and continuous ring of marginal setae (illustrated in Caldwell 1940 for S. elongagena  ); while in contrast, the reticulata  group are characterized by non-wax producing tubercles and tentacles and lack a contiguous marginal ring of setae (Figs 12-13). However, currently immatures are known for these three species only, so it remains to be tested whether these highly distinct immature morphologies reflect species group assignments.

Note on adult assignment to species group.

The two species groups ( elongagena  group and reticulata  group) are most easily recognized by the shape of the female terminalia, e.g., extremely convex apex of female proctiger in the elongagena  group, versus more or less dorsally straight and tapering in the reticulata  group. The elongagena  group females have a FP:HW ratio typically < 0.70 (range 0.51-0.69), and FP:RL ratio typically < 2.18 (range 1.41-2.19); whereas in the reticulata  group FP:HW ratio is typically > 0.70 (range 0.69-0.95), and FP:RL ratio is typically > 2.18 (range 2.17-2.59). Swezeyana  males are less easily assigned to a species group, but elongagena  group males have a distal aedeagus segment that is typically shorter than the paramere (PL:AEL ratio range 0.92-1.60), whereas reticulata  group males have a distal aedeagus segment that is longer than the paramere (PL:AEL ratio range 0.65-0.88). Notably, the fore wing characters used by Zimmerman (1948) to key out the two species described by Caldwell ( S. elongagena  and S. reticulata  ), such as presence/absence of cross veins in cell r1 and presence/absence of distinct patterns of pigmentation are found in both species groups. The key below does not key to species group, rather it employs characters useful in distinguishing species, in particular those co-occurring on the same island.

Note on molecular analyses.

The neighbour-joining analysis of two mitochondrial DNA regions is presented in Fig. 2. Strong support is recovered for the reticulata  group, but not for the elongagena  group. The topologies recovered in comparative ML and Bayesian analyses differ only at weakly or unsupported nodes. The three nodes that group same island sister taxon pairs (on Kauai, Oahu, and Hawaii) are recovered in all analyses but with variable support (much stronger support in the Bayesian than NJ or ML analyses) (see Fig. 2 and Discussion). Maximum genetic divergence (uncorrected p-distances) among Swezeyana  species is 19.9%; maximum intraspecific divergence (3%) was found in S. magnaccai  on Oahu.

Key to Swezeyana  adults

Note on species descriptions.

Swezeyana  is a small genus with, in general, considerable morphological homogeneity. The species descriptions below provide details of species specific characteristics not supplied in the generic description above.