Adrothrips Moulton, 1942

Mound, Laurence A., Tree, Desley J. & Wells, Alice, 2022, Convoluted maxillary stylets among Australian Thysanoptera Phlaeothripinae associated mainly with Casuarinaceae trees, Zootaxa 5190 (3), pp. 301-332 : 304-305

Adrothrips Moulton

Adrothrips Moulton, 1942: 4 .

Type species Adrothrips aureus Moulton , by monotypy.

Described as monotypic, this genus was subsequently revised to include five species ( Mound 1970), although seven more new species are described below. There is considerable structural diversity among these 12 species, including the length of the maxillary stylets, and in females the form of the tube, the tenth abdominal segment. This terminal abdominal segment is simple and tubular in most of the species, but unusually short in one species ( vernoni sp.n.), and with the basal half broadly swollen in four species (acanthus, aureus , cotteri and mitchelli sp.n.). However, the length of the maxillary stylets is not correlated with the form of the tube, such that aureus and cotteri have a similar remarkable tube ( Figs 33–34 ), but cotteri has shorter stylets that are similar to those in vernoni ( Figs 13 , 20 ) in contrast to the long stylets of aureus ( Fig. 12 ). Ten of the species lack a sense cone on antennal segment III but in two species this sense cone is present. However, these two are also probably not closely related, because the maxillary stylets are rather short in lihongae sp.n. but arranged into coils in latrarei sp.n. ( Figs 15–16 ). The variation in stylet lengths among the various species is possibly related to differences in the feeding sites, such that the species with exceptionally long and coiled stylets live on green branchlets, as discussed by Mound (1970). However, at least one of the species with shorter stylets ( vernoni sp.n.) seems to live either in galls or on the split surface of young woody stems. The genus Adrothrips is most likely related to the complex of Rhopalothripoides species that live on the split stems of young branches of Acacia species ( Crespi et al. 2004).

Diagnosis. Small pale, bicoloured or light brown, macropterous or micropterous Phlaeothripinae , usually with exceptionally long maxillary stylets. Head little longer than wide; postocular setae small and capitate; maxillary stylets deeply retracted into the head, usually crossing each other or rarely touching medially, usually with one or more convolutions near base of head. Antennae 8-segmented; III usually with no sense cones but sometimes with 1, IV with 2 ventral sense cones; V slightly asymmetric at apex; VI broadly truncate at apex, VII not narrowed at base; VIII small. Pronotal major setae small with expanded apices, usually all 5 pairs present but am and ml sometimes not developed; notopleural sutures complete. Prosternal basantra absent, mesopresternum transverse, or reduced to two sclerites, or absent; metathoracic sternopleural sutures long, sometimes eroded. Mesonotal midlateral setae very small, apex expanded. Metanotum with several pairs of small setae. Fore tarsal tooth present in female, usually present in male; fore tibia rarely with an apical tubercle. Fore wings evenly wide, without duplicated cilia; 3 short sub-basal setae present with expanded apices. Pelta broadly triangular; tergites II–VII usually with 2 pairs of sigmoid wing-retaining setae, anterior pair small or absent; tergal posteromarginal setae S1 broadly expanded, arising very close to wing-retaining setae; posteroangular setae small on tergites II–VI; tergite IX setae S1 and S2 short and capitate, S3 acute; tube shorter than head, sometimes strongly reticulate and expanded. Male tergite IX setae S2 similar to setae S1; sternite VIII with no pore plate, but median sternites sometimes with transverse band of specialised reticulation.

Key to Adrothrips species

1. Antennal segment III with one long sense cone, this segment about 2.5 times as long as wide, ( Figs 5–6 ); pronotal anteromarginal and midlateral setae minute............................................................................. 2

-. Antennal segment III with no sense cones, this segment usually less than 2.0 times as long as wide; pronotal anteromarginal and midlateral setae small but capitate........................................................................ 3

2. Antennal segment III simple at base ( Fig. 6 ); maxillary stylets broadly crossing over each other with one large posterolateral loop ( Fig. 15 ).............................................................................. lihongae sp.n.

-. Antennal segment III with sharp-edged sub-basal disc ( Fig. 5 ); maxillary stylets with about three posterolateral coils ( Fig. 16 ).......................................................................................... latrarei sp.n.

3. Maxillary stylets with posterolateral coils or convolutions ( Figs 14, 17–18 )....................................... 4

-. Maxillary stylets not coiled or convoluted, with no more than one curve laterally................................... 6

4. Head about 1.8 as long as wide ( Fig. 17 ), vertex with weak longitudinal reticles with no internal markings...... madiae sp.n.

-. Head as wide as long, with vertex reticulate and reticles having internal markings.................................. 5

5. Maxillary stylets with 3-6 clearly defined coils posterolaterally ( Fig. 14 ); head largely yellow, metanotum with U-shaped brown marking..................................................................................... intermedius

-. Maxillary stylets with two irregular convolutions posterolaterally ( Fig. 18 ); head metanotum largely brown with median area pale.......................................................................................... systenus

6. Maxillary stylets widely crossing over each other medially in head ( Figs 11–12 )................................... 7

-. Maxillary stylets close together medially or only weakly crossing over each other ( Fig. 13 ).......................... 10

7. Tergites VIII–IX posterolaterally with several short stout spines ( Fig. 32 )................................... akanthus

-. Tergites VIII–IX without short stout spines................................................................. 8

8. Antennal segment III usually at least 2.0 times as long as wide ( Fig. 2 ); fore tibia with papilla-like tubercle near inner apex [tube of female strongly sculptured and angulate medially with distal third sharply narrower ( Fig. 33 )].................. aureus

- Antennal segment III no more than 1.1 times as long as wide ( Figs 9, 10 ); fore tibia without a tubercle at inner apex....... 9

9. Female with tube strongly sculptured on basal half ( Fig. 36 ); antennal segment III evenly narrowing to basal pedicel ( Fig. 10 )......................................................................................... mitchelli sp.n.

- Female with tube without sculpture, evenly narrowing to apex ( Fig. 39 ); antennal segment III sharply narrowed to basal pedicel ( Fig. 8 )................................................................................... westoni sp.n.

10. Antennal segment III at least 1.5 times as long as wide ( Fig. 3 ); tube of female sharply constricted on distal half with expanded basal half strongly sculptured ( Fig. 34 ); fore tibia of female with sub-apical tubercle on inner margin; mesopresternum of female fully developed and transverse................................................................. cotteri

-. Antennal segment III short, as wide as long ( Fig. 8 ); female with tube short, weakly constricted medially ( Fig. 38 ); fore tibia without sub-apical tubercle; mesopresternum strongly eroded........................................ vernoni s p.n.

Figures

FIGURES 28–39. Adrothrips prosternites and abdomen. (28) cotteri; (29) latrarei; (30) lihongae; (31) vernoni; (32) akanthus; (33) aureus; (34) cotteri; (35) intermedius; (36) mitchelli; (37) systenus; (38) vernoni; (39) westoni.

FIGURES 11–19. Adrothrips heads. (11) acanthus; (12) aureus; (13) cotteri; (14) intermedius; (15) lihongae; (16) latrarei; (17) madiae; (18) systenus; (19) westoni male.

FIGURES 20–27. Adrothrips heads, metanotum & pelta. (20) vernoni holotype; (21) mitchelli holotype; (22) aureus; (23) intermedius; (24) latrarei; (25) madiae; (26) vernoni; (27) systenus.

FIGURES 2–10. Adrothrips species antennae. (2) aureus; (3) cotteri; (4) intermedius; (5) latrarei; (6) lihongae; (7) madiae; (8) vernoni; (9) westoni; (10) mitchelli.