Myrciathrips variabilis, Cavalleri & Lindner & Mendonça Jr, 2016

Cavalleri, Adriano, Lindner, Mariana F. & Mendonça Jr, Milton de S., 2016, New Neotropical Haplothripini (Thysanoptera: Phlaeothripidae) with a key to Central and South American genera, Journal of Natural History 50, pp. 1389-1410 : 1407-1408

Myrciathrips variabilis sp. nov.

Macropterous female. Body brown; fore tibiae and tarsi yellow, middle and hind tibiae brown; antennal segment I concolorous with head, II brownish on basal half and yellowish at tip, III and IV yellow, V and VI lightly shaded with brown at apex, VII and VIII brown; fore wing pale, without median dark line; major setae on head and thorax yellow; tergite X dark brown in basal 2/3 and paler at apex.

Head about 1.7 times as long as greatest width, cheeks slightly curved; po close to cheeks and expanded at tip, about half the eye length; maxillary stylets retracted to po level and about 1/3 of head width apart, maxillary bridge present; mouth cone short (scarcely reaching basantra) and rounded at tip; antennal segment III with two and IV with four sense cones.

Pronotum trapezoidal, with a dark longitudinal median line; only pa and epim welldeveloped, aa, am and ml similar in size to discal setae; prosternum with well-developed ferna, basantra about as broad as long; mesonotum with elongate reticles at anterior region; metanotum with equiangular reticulation anteromedially, and with one pair of long and pointed setae medially; duplicated cilia on fore wings present but variable in number (nine to 13). Fore femora enlarged, fore tibiae shorter than mid and hind tibiae and curved, fore tarsi with large hamus and strong tooth. Pelta triangular, with paired campaniform sensilla, reticulation well defined and arcuate anteromedially, tergites II–VII each with two pairs of wing-retaining setae, sometimes with an additional pair of wing retaining setae (more frequent on III–V); tergite IX setae S1 softly pointed, S2 and S3 finely acute, all about the same size; tergite X with anal setae about as long as tube. Sternites with three pairs of posteromarginal setae, median pair distinctly longer, and about 15–20 discal setae, placed in a single row.

Measurements of female (holotype), in microns (µm): length about 2547; head length 305, greatest width across cheeks 182, po length 42; median length of pronotum 242, width 308, epim length 75, pa length 50; tergite X length 172, basal width 75, apical width 35; length (width) of antennal segments III–VIII 67 (35), 70 (37), 62 (32), 55 (27), 45 (22), 35 (12), respectively.

Macropterous male. Smaller than but similar to female in colour; pa setae sometimes reduced, but longer than discal setae; duplicated cilia on fore wings present; fore femora and pronotum not as enlarged as in females, fore tarsi with smaller tooth; transverse pore plate on sternite VIII occupying almost all sternite area; S2 setae on abdominal tergite IX short and pointed.

Measurements of male (paratype): length about 1184; head length 256, greatest width across cheeks 160, po length 26; median length of pronotum 172, width 240, epim length 57, pa length 12; tergite X length 152, basal width 57, apical width 30; length (width) of antennal segments III–VIII 57 (30), 62 (30), 57 (27), 50 (21), 42 (18), 27 (11), respectively.

Larvae are uniformly red in colour, and all immature stages were found coexisting with Holopothrips inside Myrcia guianensis galls.

Type material

Holotype female, Brazil, São Francisco de Paula (29°29’16”S, 50°12’04”W), from Myrcia guianensis gall (induced by Holopothrips ), 9 September 2011 (Shizen, T. col.) ( UFRGS 2446). Paratypes: 24 females and 10 males with same data as holotype.

Remarks

The generic relationships of this new taxon are not easy to access, considering its remarkable morphology. The number of sense cones on antennal segments III and IV is typical of Haplothrips , although this character is known to be highly variable in that genus ( Mound and Minaei 2007). However, M. variabilis contrasts with Haplothrips members in having the head unusually long and only two pairs of long setae on the pronotum. An elongate head evolved several times within Haplothripini and also occurs in most Leptothrips and some Karnyothrips . The short and pointed sub-basal setae on the fore wings are also observed in some Podothrips , such as the Brazilian P. bambusae Hood which also shows short pronotal aa, am and ml setae and enlarged fore legs. The presence of enlarged fore legs and additional sigmoid wing-retaining setae is also found in such Haplothripini as Euoplothrips and Mesothrips , both also presumably invaders of thrips leaf-galls from the Oriental and Pacific regions ( Mound and Minaei 2007). Our observations suggest that M. variabilis is phytophagous on gall tissue, and we did not detect predation on the gall-inducing Holopothrips . No individuals were collected outside the M. guianensis galls, and this association is likely to be specific.