![Heads of urothripines. (21) Amphibolothrips grassii; (22) A. knechteli; (23) A. marginatus; (24) Bebelothrips flavicinctus; (25) Conocephalothrips tricolor; (26) Bradythrips hesperus; (27) Baenothrips cuneatus; (28) B. murphyi; (29) S. erythrinus; (30) B. guatemalensis; (31) B. moundi; (32) Stephanothrips uvarovi [paratype].](https://www.researchgate.net/profile/Elison-Lima/publication/372547203/figure/fig2/AS:11431281176434096@1690164629636/FIgures-21-32-Heads-of-urothripines-21-Amphibolothrips-grassii-22-A-knechteli_Q320.jpg)
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ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Accepted by A. Cavalleri: 29 Jun. 2023; published: 24 Jul. 2023 91
Zootaxa 5319 (1): 091–102
https://www.mapress.com/zt/
Copyright © 2023 Magnolia Press Article
https://doi.org/10.11646/zootaxa.5319.1.6
http://zoobank.org/urn:lsid:zoobank.org:pub:F74A47A2-8711-45A5-856E-804C16B3C4C1
Licensed under Creative Commons Attribution-N.C. 4.0 International https://creativecommons.org/licenses/by-nc/4.0/
What is a genus—interpreting structural diversity among species of urothripine
Phlaeothripinae (Thysanoptera)
LAURENCE A. MOUND, ÉLISON FABRÍCIO B. LIMA & CHERYLE A. O’DONNELL
1Australian National Insect Collection, CSIRO. GPO Box 1700. Canberra, Australia. 2601.
�
laurence.mound@csiro.au; https://orcid.org/0000-0002-6019-4762
2Universidade Federal do Piauí, Campus Amílcar Ferreira Sobral, PPG em Biodiversidade e Conservação. BR 343, Km 3.5. Floriano,
PI, Brazil. 64808-605.
�
efblima@ufpi.edu.br; https://orcid.org/0000-0002-6361-0928
3United States Department of Agriculture, Animal, Plant, Health Inspection Services, Plant Protection Quarantine, Plant Health
Programs, National Identification Services. 10300 Baltimore Avenue, Beltlsville, MD, USA. 20705.
�
cheryle.a.odonnell@usda.gov; https://orcid.org/0000-0002-2260-9998
Abstract
Variation within and between species is discussed in several obvious character states, including the number of visible
antennal segments, prolongation of the anterior margin of the head, metaepimeral setae, and anal setae. As a result,
Bebelothrips and Conocephalothrips are considered new synonyms of Amphibolothrips, and Baenothrips a new synonym
of Stephanothrips. The revised generic classification suggests that urothripines are largely absent from the Neotropics,
with four recorded species all likely to be introductions from the Old World.
Key words: variation, antennal segmentation, new synonymies, geographic distribution
Introduction
A genus is an hypothesis, representing the opinion of one or more taxonomists concerning the structural relationships
of a group of species, although it may be a single species that exhibits no character states that associate it with any
pre-existing genus. As an hypothesis, a genus is subject to testing against new data, both structural or molecular, but
it remains dependent on the interpretations and opinions of individual taxonomists. And a similar caveat applies to
all taxonomic categories. Homoplasy amongst morphological features, the occurrence of similar states in species
not closely related, is a recurrent problem in attempts to understand phylogenetic relationships within the insect
order Thysanoptera (Minaei & Mound 2021). The generic classification of the urothripines, a worldwide group
of mainly flightless species of Phlaeothripinae, reflects this issue. For this group of fungus feeding species, living
mainly in leaf litter and at the base of grasses but sometimes on dead branches, most taxonomic studies have been
based on small samples or even single specimens, and by various workers in different parts of the world.
This led to an emphasis on single unusual character states, autapomorphies, and thus the erection of many
monobasic genera. Structural similarities amongst these genera resulted in Stannard (1952, 1957) synonymizing
under Amphibolothrips the nine urothripine generic names that were available up to the 1950’s. These synonymies
proved unacceptable to other workers who, during the 1960’s, added five further monobasic genera to the group. In
response, Stannard (1970) re-validated the 15 genera by then available, added two further new genera, and attempted
to re-evaluate their relationships. However, his illustrated “phylogenetic tree” of the 17 genera was of limited
evolutionary significance, not being based on a phylogenetic framework, and some of the quoted geographical
distributions are now considered incorrect. The next attempt to rationalize this generic classification (Mound 1972)
included synonymizing four genera under Baenothrips. Subsequently, two further genera were synonymized under
Urothrips by Ulitzka and Mound (2014), together with a discussion of some of the taxonomic problems associated
with this group. The only other major publication on this group accepted that generic classification and provided
keys to 12 species in five urothripine genera recorded from China (Tong & Zhao 2017).
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92 · Zootaxa 5319 (1) © 2023 Magnolia Press
FIGURES 1–20. Antennae of urothripines. (1) Amphibolothrips grassii; (2) A. knechteli; (3) Conocephalothrips tricolor; (4)
Bebelothrips flavicinctus; (5) Baenothrips guatemalensis; (6) B. moundi; (7) B. chiliensis; (8) B. cuneatus; (9) Bradythrips
hesperus; (10) Stephanothrips buffai; (11) S. uvarovi (paratype); (12) S. uvarovi (Brazil); (13) S. howei; (14) S. barretti; (15)
S, broomei; (16–17) S. erythrinus (paratypes); (18) S. austrinus; (19) S. adnatus; (20) Antennae of five Asian Stephanothrips
species in Okajima (1989).
SPECIES OF UROTHRIPINE PHLAEOTHRIPINAE (THYSANOPTERA) Zootaxa 5319 (1) © 2023 Magnolia Press · 93
The generic classification of urothripines is re-opened here because several other genera seem equally poorly
supported. In particular, Baenothrips is currently distinguished from Stephanothrips on the grounds that antennal
segments III–V are either separate from each other or are fused into a single unit. But when every described species
is considered, these two conditions are by no means distinct (Fig 5–19). Moreover, the fusion of antennal segments
does not seem to be closely correlated with any other character states. For example, although several species placed
in Baenothrips have a pair of prominent setae laterally on the metaepimera, including the type species guatemalensis,
other species placed in that genus lack these setae, as do all of the species placed in Stephanothrips. The situation
becomes even more confusing when considering the polarity of such character states, leading to the conclusion that
some states have been subject to reversal.
The objectives here are to review the various attempts at generic classification of urothripines, to discuss patterns
of variation in this group in several characters, to place three further generic names into synonymy, to present a
new identification key to the seven genera of urothripines accepted here, and to look for correlations between these
genera and their geographical distributions.
Character state variation
Antennal segmentation: Okajima (1989) described five new species of Stephanothrips from parts of Malaysia
and Indonesia, and his published illustration of their different antennae is reproduced here (Fig. 20). One species
has antennae similar to that of the type species of the genus, S. buffai from South Africa, with segments III–V
completely fused, and VI–VIII fused but with a faint transverse line ventrally. In the other four species, segment V
is sometimes weakly indicated but in each one VI is distinct, with VII fused to VIII only in one species. However,
in Australia a similar condition with antennal segments III–V completely fused occurs in S. howei with S. barretti
showing an intermediate condition (Figs 10–14). Similar patterns of variation in the extent of fusion occur amongst
the species here placed in Amphibolothrips (Figs 1–4), as well as those in Urothrips. The two species placed in the
genera Habrothrips and Octurothrips have retained the plesiomorphic antennal condition of eight free segments
(Figs 40, 43). Among the other urothripines, fusion between antennal segments is not only a derived condition, it
has occurred convergently on multiple occasions, as indicated in Figures 1–20. As a result of the unstable visible
antennal segmentation in this lineage, the number of antennal segments is here considered too variable to provide a
useful distinction at genus level.
Head projection: Five species are here considered to be members of Amphibolothrips, and four of these have the
vertex projecting over the bases of the antennae. Similarly, among the seven species of Urothrips the vertex projects
in three species, although in most members of the urothripine group this condition is not found. The head projection
of Habrothrips is not homologous because the antennae arise at the apex (Fig. 40).
Cephalic setae: Almost two–thirds of the 81 species currently listed in this group have one to three pairs of
prominent setae on the anterior margin of the vertex (Figs 26–32), and all of these species are here placed in the
genera Bradythrips and Stephanothrips (plus Baenothrips) The most common condition is the presence of three
pairs of these setae, one pair close to the midline and two pairs closer to the eyes, and logically this is likely to be the
most highly derived condition. The length of these setae varies greatly between species, one Stephanothrips species
lacks the median setal pair, and the six species of Bradythrips have only the median pair and not the lateral pairs.
This is discussed further below, because complete absence of these setae may not be an independent state but merely
part of a series from zero to three.
Fore tarsal hamus: The two species in Habrothrips and Octurothrips have a hamus on the fore tarsus similar
to that found widely amongst Phlaeothripidae, projecting ventro-medially. In contrast, all except one of the 12
Urothrips species have a hamus that projects laterally on the external margin of each fore tarsus. A similar external
lateral hamus is found in the widespread species Stephanothrips occidentalis, and this condition is considered
further below under relationships.
Metaepimeral setae: These setae are prominent laterally in Habrothrips and Octurothrips, the two genera that
have retained the plesiomorphic condition of the antennae. These setae are also prominent in the type species of
Baenothrips as well as in at least six other species previously placed in that genus. However, they are not present
in four species placed in Baenothrips from Australia, nor in one from India. Prominent metaepimeral setae do not
occur in any other member of the urothripine group, although the type species of Bradythrips has a small pair of
apparently homologous setae in this position.
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94 · Zootaxa 5319 (1) © 2023 Magnolia Press
FIGURES 21–32. Heads of urothripines. (21) Amphibolothrips grassii; (22) A. knechteli; (23) A. marginatus; (24) Bebelothrips
flavicinctus; (25) Conocephalothrips tricolor; (26) Bradythrips hesperus; (27) Baenothrips cuneatus; (28) B. murphyi; (29) S.
erythrinus; (30) B. guatemalensis; (31) B. moundi; (32) Stephanothrips uvarovi [paratype].
Anal setae: Species in this group typically have three pairs of very long setae at the apex of the tenth tergite, the
tube (Figs 39, 42). However, the mid-dorsal pair is often rather shorter than the other two pairs. In one species from
Australia, bulbosus, this pair is scarcely 0.3 as long as the two lateral pairs, and in caenosus the median dorsal pair
of setae is represented by minute papillae. Even more remarkably, in tricolor from Hawaii these setae are flattened
and scale-like, and less than 10 microns long.
SPECIES OF UROTHRIPINE PHLAEOTHRIPINAE (THYSANOPTERA) Zootaxa 5319 (1) © 2023 Magnolia Press · 95
FIGURES 33–42. Heads of urothripines. (33) Urothrips paradoxus; (34) U. calvus; (35) U. tarai; (36) U. reedi; (37) U.
junctus; (38) U. probolus. (39–40) Habrothrips curiosus. (41–42) Octurothrips pulcher.
MOUND ET AL.
96 · Zootaxa 5319 (1) © 2023 Magnolia Press
Generic relationships
In the key to genera below the first three genera seem to be fully distinct. However, couplet 4 relies on the presence/
absence of cephalic setae as being independent states, and as indicated above this is not entirely logical. Urothrips
calvus lacks a fore tarsal hamus and could equally well be considered a species of Stephanothrips that lacks cephalic
setae. And the available specimens of Amphibolothrips are all slide mounted in such a manner that “absence” of a
fore tarsal hamus may be due to an inability to see such a small structure. As a result, the final four genera in the key
remain less than satisfactorily diagnosed from each other, and are retained here with considerable doubts. The only
published molecular data on urothripines (Buckman et al. 2013) resolved the only available species as external to all
other Phlaeothripidae, despite the morphological structures suggesting a more highly derived group of species.
Geographic distributions
The generic classification of the urothripines presented here suggests some interesting geographic distributions.
Amphibolothrips, as treated below, is southern Palaearctic in distribution, but with tricolor known only from two
specimens taken at Oahu on the Hawaiian Islands. In the absence of further specimens, it is not possible to know if
tricolor is native to those islands, or if it has been introduced from the northern hemisphere. In contrast, Trachythrips
is known only from the New World, although only one of the 11 species has been described from South America, the
others being from Panama, the Caribbean Islands and southern USA.
The two genera that are interpreted as retaining most characters in a plesiomorphic state are the monobasic
Habrothrips and Octurothrips. These two are both from the Old World, in eastern Asia and/or Australia, but do
not seem to form a monophyletic sister-group to the other extant urothripines. Instead, based on their structural
differences they may even be two independent basal lineages. Urothrips is also widespread across the Old World
tropics, from Africa to Australia. The genus that is interpreted as having the most characters in the derived state,
Stephanothrips, is by far the most species rich. These species have the derived condition of antennal segments III–V
more or less fused (Figs 10–19), whereas in the closely related Bradythrips the plesiomorphic condition is retained
with antennal segments III–V distinct from each other (Fig. 9). These two genera are here considered to be Old
World, with the few species reported from the Neotropics in the genera Baenothrips and Stephanothrips considered
below as more likely to have been introduced by human trading.
The single known specimen of Baenothrips guatemalensis was actually taken in quarantine at San Francisco,
USA, in association with an orchid plant said to have been imported from Guatemala. Given the doubts accompanying
such quarantine records, the country of origin of this thrips specimen remains uncertain. A closely similar species,
B. chiliensis, has been seen in several samples from Chile where it is clearly established. However, both chiliensis
and guatemalensis are remarkably similar in structure and sculpture to B. moundi, a species that is widespread
in leaf-litter across the continent of Australia. We suggest that these three names are likely to refer to a single
species that varies slightly in colour and in the degree of antennal fusion. This conclusion seems to be rather more
likely than an alternative hypothesis of an independent radiation in South America. The third urothripine recorded
exclusively from the Neotropics, Stephanothrips erythrinus, remains known only from the original specimens taken
in Argentina at another site near the west coast of South America (Figs 16–17). This species shares most character
states with some southeast Asian species listed in Baenothrips that have reticulate sculpture on the vertex, including
asper, minutus, murphii and ryukyuensis. Again, this species has possibly been introduced from Asia rather than
representing an independent Neotropical radiation. A fourth urothripine species taken in the Neotropics is a species
of Stephanothrips known from two females taken by J.D. Hood in 1948 at two sites in Brazil in the state of São
Paulo, and one female taken in 2011 at Porto Alegre in the state of Rio Grande de Sul. The latter specimen has
been compared directly with specimens of two Stephanothrips species from southern Africa: S. buffai (identified
by zur Strassen from Congo, South Kivu), and a paratype of S. uvarovi from Cape Province, South Africa (Figs
11–12). No significant differences could be found between the specimens from Brazil and uvarovi, they both have
the pronotum and abdominal tergites bicoloured, and this again raises the question of Neotropical endemicity or
introduction. Considering the many studies on Thysanoptera of the Neotropics by J.D. Hood and D. Moulton,
including extensive leaf-litter sampling (Mound 1977), it is remarkable how few specimens of this distinctive and
interesting urothripine group have been reported from South America. This lack of collections provides no support
SPECIES OF UROTHRIPINE PHLAEOTHRIPINAE (THYSANOPTERA) Zootaxa 5319 (1) © 2023 Magnolia Press · 97
for any hypothesis that the urothripines have diversified independently in the Neotropics. In contrast, it lends further
credence to the possibility that all four members of this group recorded from South America represent introductions
from overseas.
The possible origins of such disrupted distributions of small insects were discussed by Mound (1970: 88) in
connection with the ballast (and galley-fire wood) carried by the vast tonnage of sailing ships in the 18th and 19th
centuries. Sailing ships had to be trimmed to float at a particular level in the water (the Plimsoll line), and this was
achieved, only after the cargo was loaded, by adding or removing ballast to or from the “ballast quay” (Mound 1970,
1983). Biologists with an interest in distributions need to remember the extent of this sailing ship trade that lasted for
over 300 years. Portugal had a vigorous trade with the Asian “spice islands”, with southeast Africa and with Brazil,
and Britain had a similar extensive trading pattern. In east Africa, Germans imported and created a central European
forest with imported plants in huge tubs of soil, and British settlers in Australia tried to make parts of that continent
“look like home” through the activity of “acclimatisation societies”. It should not surprise us that many organisms,
including weedy plants and insects, also some fungus-feeding thrips, survived such voyages to entirely new parts of
the world.
Distinguishing the Urothripine genera
1. Compound eyes each with at least 30 facets (Figs 40–41), all equal in size; antennal segment III slender, usually 3–4 times
as long as wide and not narrowed sharply to base; mid and hind tarsi 2-segmented; fore tarsal hamus directed ventrally;
metathoracic epimera each with a prominent lateral seta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
-. Compound eyes never with more than 15 facets (Figs 27–28), some dorsal facets much larger than others; antennal segment
III almost globose, scarcely 2 times as long as wide and sharply narrowed to basal stem (sometimes fused to segment IV or
to IV+V); mid and hind tarsi 1-segmented; fore tarsal hamus, when present, directed laterally; metathoracic epimera with or
without such a seta ....................................................................................3
2. Head projecting over bases of first antennal segment (Fig 41); eyes almost holoptic but with no facets ventrally; head with
genae narrowing to base; prosternal basantra present and transverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Octurothrips
-. Head projecting strongly in front of eyes with antennae arising at apex (Fig. 40); compound eyes globose on dorsal and ventral
surfaces; head sharply narrowed to base; prosternal basantra reduced to weak sclerites placed anterolaterally . . . . Habrothrips
3. Prosternal basantra transverse across anterior margins of ferna .........................................Trachythrips
-. Prosternal basantra absent or reduced to small anterolateral sclerites .............................................4
4. Anterior margin of head with prominent setae, rarely reduced to a single small pair (Figs 26–32) ......................5
-. Anterior margin of head with no prominent setae (Figs 33–38) .................................................6
5. Antennal segment III narrowed at apex and distinct from narrowed base of IV (Fig. 9); maxillary stylets close together medially
in head .....................................................................................Bradythrips
-. Antennal segment III broad at apex and close to broad base of IV, segments III–V weakly to closely fused; maxillary stylets
about 0.3 of head width apart .................................................................Stephanothrips
6. Fore tarsus with hamus ..........................................................................Urothrips
-. Fore tarsal hamus absent ...................................................................Amphibolothrips
Amphibolothrips Buffa
Amphibolothrips Buffa, 1909: 193. Type species Amphibolothrips grassii Buffa.
Bebelothrips Buffa, 1909: 195. Type species Bebelothrips latus Buffa. Syn.n
Conocephalothrips Bianchi, 1946: 499. Type species Conocephalothrips tricolor Bianchi. Syn.n.
Buffa (1909) erected this genus for a single species, grassii, based on a single specimen from Lake Albano near
Rome, in Italy. This species is currently recorded also from southern France and Spain. In the same paper, Buffa
also erected Bebelothrips for a single species, latus, based on three females from Isola del Giglio, an island between
the west coast of Italy and Corsica. The original specimens of both species are currently not known to exist,
however Trachythrips flavicinctus Bournier from southern France is now considered a synonym of latus. The genus
Bebelothrips has remained distinguished from Amphibolothrips based only on the differing number of antennal
segments (Priesner 1964). However, despite the larger number of antennal segments, Stannard (1970) transferred
Trachythrips marginatus Bournier from southern France to Amphibolothrips, and Mound (1972) similarly transferred
Bebelothrips knechteli Priesner, a species that is recorded only from Romania and the Canary Islands.
Bianchi (1946) erected Conocephalothrips for the single species tricolor, and this remains known only from
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98 · Zootaxa 5319 (1) © 2023 Magnolia Press
two females collected on Oahu. The new genus was compared only to Urothrips and no mention was made of
Amphibolothrips although the head of grassii, the only species of the genus known at that time, is similarly produced
forward over the antennal bases (Figs 21–25). The antennal segments of grassii are more extensively fused than in
tricolor, in which antennal segments III–V are distinct but broadly joined (Figs 1–3). The antennae of Bebelothrips
latus, and also of the other two species now placed in Amphibolothrips, are intermediate in structure between grassii
and tricolor. The body of the holotype of tricolor has too much pigment for basantra to be visible, but the species is
unusual in having the dorsal pair of anal setae flattened and scale-like, and less than 10 microns long.
It is not possible to know if the species tricolor is a natural inhabitant of the Hawaiian Islands, or if it has been
introduced to Oahu from some other part of the world. In the northern part of North America almost nothing is
known of the leaf litter thrips fauna, but the other four species here recognised in Amphibolothrips are all from the
southern parts of Europe. However, despite the interpretation adopted here of the available data, there is a further
problem in distinguishing Amphibolothrips from Urothrips. The distinction between these indicated above in the
key to genera fails with just one of the 12 described species of Urothrips. The fore tarsal hamus of calvus from
eastern China appears to be absent, although it is also very small in lancangensis from southern China.
The new synonymy of Bebelothrips and Conocephalothrips with Amphibolothrips results in two new
combinations as listed in Table 1.
Bradythrips Hood & Williams
Bradythrips Hood & Williams, in Hood, 1925: 68. Type species Bradythrips hesperus Hood & Williams.
The type species was based on a single wingless female collected in Guyana, on the north coast of South America.
However, at the U.S. National Museum in Washington and in the collections of Universidade Federal do Piauí,
Floriano, in Brazil, we have studied in addition to this holotype the following wingless females of B. hesperus:
one from Panama, seven from Guyana, and more than 10 from Brazil along the Amazon River basin (States of
Amazonas, Pará and Amapá). In contrast, the other five species that are now known in this genus are all from
southeast Asia, including Malaysia, southern China, Philippines and Borneo, and specimens of hesperus have also
been recorded from India, Borneo and the Solomon Islands (Okajima 1987). These records indicate that Bradythrips
is likely to be a genus of the Asian tropics but with one species that has been inadvertently transported to South
America, probably by sailing ships.
A key to five of the six species of Bradythrips is available (Okajima & Urushihara 1995a), and of the two species
with the pronotum and fore legs yellow, zhangi differs from hesperus in having the head more uniformly brown and
the abdominal tergites with narrow longitudinal sculpture medially. All six species have antennal segments III–V
clearly distinct from each other, in contrast to the condition in Stephanothrips species. The members of Bradythrips
differ from those previously placed in Baenothrips in having the maxillary stylets close together medially in the
head, and only a single pair of prominent setae on the anterior margin of the head (Fig. 26). Although B. hesperus
has the metathoracic epimera bearing a small stout seta laterally, it appears that the other members of this genus lack
this structure.
Habrothrips Ananthakrishnan
Habrothrips Ananthakrishnan, 1968: 137. Type species Habrothrips curiosus Ananthakrishnan.
The single species in this genus is widely distributed in leaf-litter between India and northern Australia, and all known
specimens of both sexes are macropterae (Figs 39–40). It shares with other urothripine species the long abdominal
segments IX–X and the presence of a pair of prominent setae on the metathoracic epimera, but it exhibits several
unusual features. The following can probably be considered plesiomorphic: compound eyes large and globose,
mid and hind tarsi 2-segmented, and fore tarsal hamus directed ventro-medially. However, the following character
states are more highly derived, and are unique among urothripines: head strongly projecting in front of eyes, and
abdominal tergites with a median groove bearing two pairs of leaf-like setae that are presumably wing-retaining.
SPECIES OF UROTHRIPINE PHLAEOTHRIPINAE (THYSANOPTERA) Zootaxa 5319 (1) © 2023 Magnolia Press · 99
Octurothrips Priesner
Octurothrips Priesner, 1931: 93. Type species Octurothrips pulcher Priesner.
Known only from Australia, the single species in this genus has been found widely in the inland arid zone of the
eastern part of this continent (Figs 41–42). Although all of the available specimens are apterae, the species shares
many character states with Habrothrips curiosus, including the abdominal tergites with a groove down the midline.
However, the head is remarkable with greatly enlarged, almost holoptic. compound eyes, with the genae extending
forward laterally around the eyes, and the prosternal basantra large and transverse.
Stephanothrips Trybom
Stephanothrips Trybom, 1912: 42. Type species Stephanothrips buffai Trybom.
Baenothrips Crawford, 1948: 39. Type species Baenothrips guatemalensis Crawford, syn.n.
Verrucothrips Stannard, 1952: 128. Type species Amphibolothrips (Verrucothrips) caenosa Stannard.
Ramachandraiella Ananthakrishnan, 1964: 228. Type species Ramachandraiella minuta Ananthakrishnan.
Transithrips Bournier, 1963: 81. Type species Transithrips asper Bournier.
Bournieria Ananthakrishnan, 1966: 2. Type species Bournieria indica Ananthakrishnan.
Four of the generic synonyms indicated above were discussed by Mound (1972: 92), but the validity of Baenothrips
has not been questioned since Stannard (1952). The sole distinction between Baenothrips and Stephanothrips has
been in the degree of separation between antennal segments III–V, being separate in the first genus but largely fused
in the second. Baenothrips guatemalensis, the type species of that genus, is interpreted as having segments III–V
distinct from each other (Fig. 5), although the separation between them is by no means clear. Among the various
species placed in Baenothrips only asper and cuneatus have these segments clearly separate (Fig. 8). In the only
known specimen of guatemalensis segments VII and VIII are fused with scarcely any trace of suture, and this is
also true of chiliensis (Fig. 7). Very similar to these in structure and sculpture, the Australian species, moundi, has
segment VIII clearly distinct (Fig. 6). A further problem is that in another Australian species, B. caenosus, antennal
segments VII and VIII can be either fused or separate (Mound 1972). There is also a lack of clarity in distinctions
between some described species. For example, Bhatti (2002) published a detailed morphological study of a paratype
of asper, recognizing that specimens identified as asper from India do not represent that African species. The
original illustration of asper by Bournier, as well as the illustrations of a paratype by Bhatti, indicate that, in this
species from Angola, antennal segments III–V are clearly distinct from each other, much as in cuneatus (Fig. 8). In
contrast, the antennae of Indian specimens labelled by Ananthakrishnan as asper (Ooty, vii.1970) have segments
III–V broadly joined.
Our interpretation is that antennal segment fusion has been subject to several reversals among the various species,
and that this character state cannot be employed to distinguish natural groups. As a result, the genus Baenothrips
is here considered a synonym of Stephanothrips, and that genus will now include 47 species. These comprise 26
species from the Asian tropics, nine from Australia, three from Africa, and four from southern USA, plus four from
South America where they are possibly introduced (see above Geographic considerations). In addition, because the
only known males of occidentalis were taken in Thailand (Okajima & Urushihara 1995b), it is probable that this
pantropical species is also Asian in origin. Since several of the nine species from Australia are known only from
the northern subtropical parts of this continent, it is clear that the distribution of species in this genus is primarily in
association with the southeast Asian tropics. The new synonymy of Baenothrips with Stephanothrips results in the
15 new combinations listed in Table 1.
Trachythrips Hood
Trachythrips Hood, 1930: 317. Type species Trachythrips watsoni Hood.
Alone amongst the urothripine genera, the members of this genus have the pronotal basantra fully transverse across
the anterior margins of the ferna, although the posterior margin of the basantra is not always fully sclerotised in
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100 · Zootaxa 5319 (1) © 2023 Magnolia Press
some of the specimens examined. This character state of the basantra, paralleling the geographical distribution
of the genus, suggests a single New World radiation with the 11 members of the genus restricted to the American
continent and Caribbean islands, between California, Texas, Florida and southern Brazil. Structurally similar to
each other, the species of this genus apparently are all wingless, with some differing from others in little more than
colour patterns.
Urothrips Bagnall
Urothrips Bagnall, 1909: 126. Type species Urothrips paradoxus Bagnall.
Coxothrips Bournier, 1963: 75. Type species Coxothrips reticulatus Bournier. Synonymised by Ulitzka & Mound, 2014.
Ananthakrishnaniella Stannard, 1970: 118. Type species Ananthakrishnaniella tarai Stannard. Synonymised by Bhatti, 1998:
178.
Biconothrips Stannard, 1970: 121. Type species Biconothrips reedi Stannard. Synonymised by Ulitzka & Mound, 2014.
Within the key to genera of urothripines presented by Mound (1972), one group of four genera was distinguished
by the following three character-states: absence of elongate setae on anterior margin of head; presence of prominent
external fore tarsal hamus; reduction of prosternal basantra (=praepectus) to a pair of small triangles placed laterally.
However, there is considerable overlap in character states amongst the nine species involved under these four
generic names, and Ulitzka and Mound (2014) decided to include all nine species within a single genus, Urothrips.
The alternative to accepting a single genus to encompass the range of variation amongst these species would be
to recognise more than four monotypic genera, each of which would be supported by a single autapomorphy with
no obvious systematic significance. The problem of distinguishing genera based on characters that seem to vary
progressively in fusion or size increases when all 12 of the species now listed in Urothrips are considered. In one of
these species, U. lancangensis, the fore tarsal hamus is very small, and in U. calvus it appears to be quite undeveloped.
Similarly, the only available specimen of U. bagnalli Trybom is uncleared but seems to have transverse basantra. At
species level within the genus there appear to be further problems, in that populations of paradoxus in Africa differ
in colour details, as is known amongst populations of reedi in Australia (Mound 1972).
Acknowledgements
We are particularly grateful to Shuji Okajma for reviewing this paper and for giving us the benefit of his
extensive experience and knowledge with the Phlaeothripidae fauna of several southeast Asian countries, and to
the Zootaxa editor, Adriano Cavalleri, for his careful criticisms. Andrea Hastenpflug-Vesmanis, until recently at
the Forschungsinstitut Senckenberg, Frankfurt, and Paul Brown, until recently at The Natural History Museum,
London, kindly arranged loans of slides. Particular thanks are due to the Fulbright Commission and the Institute of
International Education, for providing funds for a visit by Elison Lima to the Smithsonian Collection housed in the
United States Department of Agriculture, Beltsville, MD, USA.
TABLE 1. Nomenclatural changes proposed here
Amphibolothrips latus (Buffa, 1909) comb. n.
Amphibolothrips tricolor (Bianchi, 1946) comb. n.
Stephanothrips asper (Bournier, 1963) comb. n.
Stephanothrips bulbosus (Mound & Wells, 2023) comb. n.
Stephanothrips caenosus (Stannard, 1952) comb. n.
Stephanothrips chiliensis (Stannard, 1970) comb. n.
Stephanothrips cuneatus (Zhao & Tong, 2016) comb. n.
Stephanothrips erythrinus (Pelikán, 1964) comb. n.
Stephanothrips goweri (Mound & Wells, 2023) comb. n.
Stephanothrips guatemalensis (Crawford JC, 1948) comb. n.
SPECIES OF UROTHRIPINE PHLAEOTHRIPINAE (THYSANOPTERA) Zootaxa 5319 (1) © 2023 Magnolia Press · 101
Stephanothrips indicus (Ananthakrishnan, 1966) comb. n.
Stephanothrips leukos (Mound & Wells, 2023) comb. n.
Stephanothrips minutus (Ananthakrishnan, 1964) comb. n.
Stephanothrips moundi (Stannard, 1970) comb. n.
Stephanothrips murphyi (Stannard, 1970) comb. n.
Stephanothrips quadratus (Okajima & Urushihara, 1995) comb. n.
Stephanothrips ryukyuensis (Okajima, 1994) comb. n.
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