Heligmothrips Mound, 1970

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 : 317-318

Heligmothrips Mound

Heligmothrips Mound, 1970: 453 .

Types species Trichothrips erinaceus Karny

This genus of dark brown, usually macropterous species of Phlaeothripinae , is a member of the Liothrips lineage, and is presumably derived from the complex of taxa associated with the genus Teuchothrips . Members of the latter genus do not usually have the maxillary stylets elongate and crossing over in the head, although two species with this condition are known from New Caledonia, both of which are associated with leaf distortion on species of Hibbertia [ Dilleniaceae ] ( Mound & Goldarazena 2022). Moreover, some specimens here identified as H. brevidens from Kangaroo Island, also H. narrabri sp.n. and H. xanthoskelus sp.n., have the stylets parallel in the middle of the head ( Figs 51–59 ). Study of species in this genus is technically difficult, because in order to study the convoluted maxillary stylets specimens must be partially bleached without disrupting the position of these stylets. In some species there is considerable variation in body size among individuals taken from the same locality and tree. Differences between specimens in colour of antennae, pronotal setae and fore wings are particularly difficult to assess. Moreover, the precise orientation of the maxillary stylets within the head is possibly not as consistent between species as indicated in Mound (1970), and the names H. erinaceus and H. gracilior (couplet 7 in key below) possibly involve a complex of species. Far more field work would be needed to establish if the observed differences are consistent, and if they are associated with different host plants, localities or seasons.

Diagnosis. Dark brown, usually macropterous Phlaeothripinae , body surface more or less reticulate. Head about as long as wide, maxillary stylets retracted to eyes and usually crossing over each other in middle of head, and each with a simple or complex loop or convolution posteromedially; mouth cone acute; postocular setae with expanded apices. Antennae 8-segmented; VII and VIII broadly joined; III with 1 sense cone, IV with 3 sense cones (2 in eiletus and narrabri ). Pronotum with 5 pairs of major setae; notopleural sutures complete. Prosternal basantra absent, ferna widely separated; mesopresternum varied, complete or with two triangles weakly joined or absent medially; sternopleural sutures long. Fore tarsus with a tooth in both sexes; fore femur enlarged in major individuals. Mesonotal lateral setae capitate, metanotal median setae usually acute. Fore wing broad and closely ciliate; duplicated cilia present (absent in narrabri ); 3 sub-basal setae present. Tergites II–VII each with 2 pairs of wing-retaining setae; tergite IX setae S1 and S2 long and capitate. Male sternite VIII with large pore plate.

Key to Heligmothrips species

1. Maxillary stylets closely parallel medially or crossing over each other, only one simple flexure posterolaterally ( Figs 51, 58 ) 2

-. Maxillary stylets crossing over each other medially (rarely parallel), with one or more complex loops or coils posterolaterally ( Figs 52–56 )......................................................................................... 5

2. Head elongate, at least 1.5 times as long as wide ( Fig. 57 ); pronotum about as long as wide and not extending fully across prothorax ( Fig. 68 )......................................................................... macropus sp.n.

-. Head broad, about 1.0 times as long as wide ( Figs 51, 58 ); pronotum transverse, in female about 2.0 times as wide as median length, in male about 1.7 times, extending fully across prothorax................................................ 3

3. Metanotal reticles large and weak, each with a spot medially ( Fig. 61 ); antennal segments IV–V uniformly brown, each with 2 sense cones; fore wings without duplicated cilia, or micropterous..................................... narrabri sp.n.

-. Metanotal reticles small and dense with no internal markings; antennal segments IV–V yellow on basal half, IV with 3 sense cones; macropterous, fore wings with duplicated cilia........................................................ 4

4. Mesopresternum divided into two lateral triangles or weakly connected medially; pronotal anteromarginal setae sometimes short but as broadly capitate as remaining 4 pairs of major setae ( Fig. 51 ); pronotal anteroangular setae of male no more than 1.5 times as long as those of female; fore wing with 12 or more duplicated cilia;............................ brevidens

-. Mesopresternum complete or narrowed medially; pronotal anteromarginal setae minute to short with weakly rounded apex; pronotal anteroangular setae of male at least three times as long as those of female; fore wing with no more than 6 duplicated cilia........................................................................................... frickeri

5. Maxillary stylets arranged posterolaterally into pair of regular coils ( Fig. 54 ); metanotal median setae stout, capitate and half as long as metanotum ( Fig. 60 ); antennal segment IV with 2 sense cones; only micropterae known................... eiletus

-. Maxillary stylets arranged posterolaterally into series of irregular loops, without regular and tight coils ( Figs 53, 56 ); metanotal median setae slender and pointed, antennal segment IV with 3 sense cones; only macropterae known................... 6

6. Head longer than wide ( Fig. 56 ), pronotum slender but slightly wider than long, narrower than prothorax width; body colour light brown with weak sculpture................................................................ exallus sp.n.

-. Head and pronotum clearly wider than long; body dark brown with head and metanotum strongly reticulate............. 7

7. All femora and tibiae yellow or brownish yellow.............................................. xanthoskelus sp.n.

- All femora dark brown, also mid and hind tibiae............................................................. 8

8 Pronotal major setae dark brown; maxillary stylets cross over each other in head at level of postocular setae, then often re-cross through a sharp angle at base of head, before producing two broad curves laterally ( Fig. 52 )................... erinaceus

-. Pronotal major setae pale; maxillary stylets cross over each other in head at the level of the postocular setae, then re-cross and produce a series of three large and complex hoops Fig. 53 ).............................................. gracilior

Figures

FIGURES 51–59. Heligmothrips species heads and stylets. (51) brevidens; (52) erinaceus; (53) gracilior; (54) eiletus; (55) eiletus larva; (56) exallus; (57) macropus; (58) narrabri; (59) xantoskelus.

FIGURES 60–68. Heligmothrips species thorax and antenna. (60) eiletus; (61) narrabri; (62) exallus; (63) xanthoskelus; (64) exallus; (65) xanthoskelus; (66) narrabri; (67) exallus antenna; (68) macropus pronotum.