Cyrilthrips, Tree & Mound, 2009

Tree, Desley J. & Mound, Laurence A., 2009, Gall-induction by an Australian insect of the family Thripidae (Thysanoptera: Terebrantia), Journal of Natural History 43 (19 - 20), pp. 1147-1158 : 1152-1156

Cyrilthrips gen. nov.

Type species: Cyrilthrips cecidis sp. nov.

Etymology

This thrips is named in honour of the father of the first author, Cyril Wallace Burcher, who was awarded the Distinguished Flying Cross in 1943 and celebrated his 90th birthday on 14 May 2008 during the course of these studies.

Generic definition

Macropterous Thripinae with inflated hind femora and recurved spur on hind coxae in females ( Figures 3G , 4E ). Antennae eight-segmented ( Figure 3C ); segment I without dorsoapical paired setae, segment II with median dorsal seta present ( Figure 4B ); segments III–IV each with prominent forked sensorium; segments III– VI with transverse rows of very weak microtrichia; segment VIII slightly longer than VII. Head small, with prominent bulging eyes ( Figure 3B ); ocellar setae I and II in transverse row anterior to fore ocellus, III absent (? or placed behind posterior ocelli) ( Figure 4F ); four pairs of postocular setae, median pair longest and close to posterior ocelli; frons with four pairs of small setae bordering eyes, also one longer pair both anteromedially and posteromedially; maxillary palps long, three-segmented. Pronotum trapezoidal ( Figure 3B ), with no long posteroangular setae, six pairs of small posteromarginal setae; discal area with about 30 small setae. Mesonotum with three pairs of setae, midlateral pair minute. Metanotum medially weakly reticulate ( Figure 3D ), median setae arising well behind anterior margin, paired campaniform sensilla present. Prosternal basantra weakly sclerotized, bearing about 10 setae ( Figure 3E ); ferna weakly joined medially. Mesothoracic furca with spinula, metafurca with spinula faintly indicated or absent. Forewings slender ( Figure 4A ), relatively short for body size, setae short, first vein with about nine setae on basal half, four on distal half; second vein with three to five setae; clavus with two to four setae, and one discal seta; posteromarginal cilia variable from straight to undulating. Tarsi two-segmented; fore tarsi with no tooth, fore tibia with small stout seta at inner apex; hind coxae with backwardly projecting curved spur in female ( Figures 3G , 4E ); hind femora inflated; hind tibia with stout spur on inner apex directed toward midline. Tergites II–VIII with broad smooth craspedum, I with narrow craspedum at least laterally; lateral thirds of tergites with about six lines of weakly reticulate sculpture bearing small dentate microtrichia, but without ctenidia, median area of tergites unsculptured; tergite VIII with spiracular area prolonged dorsoventrally but not prolonged forward; tergite IX with two pairs of campaniform sensilla, major setae with apices expanded ( Figure 3F ); X with dorsal split complete. Sternites II–VII with broad craspedum lobed between marginal setae ( Figure 3G ), II with two pairs of marginal setae, III–VII with three pairs (lateral pair commonly duplicated to produce four pairs); sternite II with three to five discal setae medially, also three pairs of minute setae near anterior margin; sternite III of female with small circular pore plate medially (IV rarely with slight indication of pore plate). Ovipositor well developed. Male smaller than female but similar in structure except: hind coxa without spur; sternite III with slender transverse pore plate, IV (rarely V) with incomplete transverse pore plate sometimes reduced to two or more circles; tergite IX produced dorsally into stout conical tubercle, bearing pair of stout but partially fused setae ( Figures 4C,D ).

Relationships

Relationships of this new genus are not clear, although it is a member of the Thripinae , the largest of the four subfamilies of Thripidae with 230 genera and 1600 species ( Mound 2008). The absence of ctenidia on the tergites indicates that it is not related to the two major genus-groups centred on Thrips and Frankliniella ( Mound 2002) . Moreover, the lack of microtrichial fields laterally on the tergites indicates that it is not related to the Scirtothrips genus-group ( Masumoto and Okajima 2007), and absence from the first antennal segment of a pair of dorsoapical setae indicates that it is not related to either the Trichromothrips or Mycterothrips genus-groups ( Masumoto and Okajima 2005, 2006). The absence of long setae on the pronotum might suggest a relationship to the Anaphothrips complex of genera ( Mound and Masumoto 2009), but a ‘‘loss-apomorphy’’ such as reduction in setal lengths is not a good basis for predicting relationships ( Mound and Morris 2007).

The enlarged spiracles on tergite VIII, and the presence of a broad craspedum on the tergites, together with a broadly lobed craspedum on the sternites, suggests that this genus is related to a group of four southeast Asian genera Danothrips , Tusothrips , Chaetanaphothrips and Aneurothrips . The members of the first of these are the most generalized in body form ( Bhatti 1980), with the craspeda weakly developed, the spiracles no larger than in Cyrilthrips , and tergite IX of the males with two pairs of stout setae that sometimes arise from separate small tubercles. The male of T. sumatrensis (Karny) bears on the ninth tergite a conical tubercle similar to that of Cyrilthrips , but with the pair of stout setae separate. Males are not known for most of the 20 species of Chaetanaphothrips , but in Ch. signipennis and Ch. machili the males bear a small tubercle on the ninth tergite with two stout setae, and an isolated unidentified male of Chaetanaphothrips has been studied from Thailand with a similar tubercle bearing a pair of setae fully fused together except at their bases. Moreover, the male of Aneurothrips priesneri Bhatti was illustrated with a similar structure in which the two setae are fused ( Bhatti 1971). All species of Chaetanaphothrips have a distinctive sculptured area on the eighth tergite that extends anteriorly from the two spiracles, and a rather similar structure is illustrated for A. priesneri . However, both species of Aneurothrips are described as having tarsi with only a single segment, the second antennal segment lacking a seta medially on the dorsal surface, and both mesothoracic and metathoracic furcae lacking a median spinula, in contrast to these characters in species of Chaetanaphothrips and Cyrilthrips . The lack of ocellar setae pair III in Cyrilthrips is unique among Thripinae ; an alternative interpretation indicated in the generic diagnosis above, that the pair of setae immediately behind the posterior ocelli might represent ocellar setae pair III, would be equally unique. From the other two genera discussed above, Cyrilthrips is also distinguished by the large number of setae on the prosternal basantra, the unique hind legs of the female with a spur on the inner margin of the hind coxae, and the expanded apices of the major terminal setae on the abdomen.

Nothing is known of the biology of Tusothrips species , but the habit in Cyrilthrips of leaf gall-induction is shared with the species of Aneurothrips , as well as with some of the 20 species of Chaetanaphothrips . Little is known of the biology of most Chaetanaphothrips and Danothrips species , apart from a few leaf-feeding species that are recorded as pests of orchids, bananas and citrus ( Mound and Marullo 1996). However, Prof. Tadaaki Tsutsumi of Fukushima University, Japan has supplied photographs of marginal leaf-roll galls on Machilus thunbergii and Machilus japonica (Lauraceae) , taken on Ishigaki-jima Island (Ryukyu Islands) in spring 2007. Some galls involved only one leaf margin, others involved both margins and resulted in a leaf becoming twisted and effectively tubular. These galls were apparently caused by the presence of adults and larvae of Chaetanaphothrips machili Hood , although some adults of other Thripidae were also present. Professor Tsutsumi further pointed out that he had seen leaf galls from Schefflera octophylla (Araliaceae) collected by Prof. Haga on Amami-ohshima Island (Ryukyu Islands), and that these galls also contained an unidentified species of Chaetanaphothrips . The Indian species, A. priesneri , is reported to induce leaf margin galls on Cordia suaveolens (Boraginaceae) , and the single known female of A. punctipennis Karny was taken in Java from a gall on the same plant species. Amphithrips argutus Ananthakrishnan , the only other known gall-inducing thripid, appears to be distantly related, because of the presence of an almost continuous row of setae on the forewing second vein, and the presence of unusually stout setae at the abdominal apex.

Figures

Figure 3. Cyrilthrips cecidis adult female. (A) Habitus; (B) head and pronotum; (C) antenna; (D) mesonotum and metanota; (E) prosternum; (F) tergites IX–X; (G) hind coxae and abdominal sternites.

Figure 4. Cyrilthrips cecidis. (A) Forewing; (B) scanning electron micrograph (SEM) of antennal segments II–III; (C) SEM of male tergite IX; (D) SEM of male tergite IX lateral view; (E) SEM of female hind coxae and sternites; (F) SEM of head dorsal view.