Tetradiplosis rayen Martínez, 2013

Martínez, Juan José, Corró-Molas, Bárbara & Alfonso, Graciela L., 2013, New species of Tetradiplosis (Diptera: Cecidomyiidae) inducing galls on Prosopis caldenia (Fabaceae) in Argentina, Zootaxa 3702 (6), pp. 587-596 : 592-595

Tetradiplosis rayen Martínez , new species

( Figs 16–26 )

Adult: Body length 4.1–5.0 mm (n= 7) Head: Eyes large, widely connate ( Fig 16 ), eye bridge about 9 facets long, facets hexagonal, closely adjacent throughout. Occiput without dorsal protuberance. Frons with 3–4 setae per side. Palpus four segmented. Labella evenly convex in frontal view, each with 6–8 lateral setae. Male third flagellomere ( Fig. 17 ) binodal, with three circumfila, first and third circumfila loops distinctly long, second circumfilum loops much shorter. Female third flagellomere ( Fig. 18 ) 3.7–3.8 times longer than its median width, with two appressed circumfila.

Thorax: Wing length, male 3.2–3.4 mm (n= 4); female 3.5–3.7 mm (n= 3). Wing veins M3, Cu1 and Cu2 fading apically ( Fig 19 ). Anepimeron with 18–23 setae. Acropods with claws bent before middle length and bidentate ( Fig. 20 ), sometimes basal tooth reduced. Empodium as long as bend in claw or slightly longer. Pulvilli slightly shorter than half the length of empodium.

Male abdomen: Tergites 1–6 rectangular with an irregular row of setae apically, a few setae laterally and a pair of anterior trichoid sensillae. Tergites 7 and 8 much shorter, and irregular in shape (similar to tergite 8 in figure 22). Tergite 7 with a few scattered setae and a pair of anterior trichoid sensilla. Tergite 8 mostly devoid of vestiture except for a pair of trichoid sensillae. Genitalia ( Fig. 21 ): Cercus well developed, as long as hypoproct or slightly longer, with the outer apical edges acute. Hypoproct bilobed. Aedeagus slender and slightly longer than hypoproct and cerci. Gonocoxites wide, not constricted in the middle. Gonostylus elongate, setulose basally.

Female abdomen: Tergites 1–7 rectangular, with an apical row of setae, a few lateral setae, and a pair of anterior trichoid sensillae. Tergite 8 very slightly sclerotized, devoid of vestiture except for a pair of trichoid sensillae ( Fig. 22 ). Cerci uniformly ovoid, not tapering apically, with a set of closely set setae apicoventrally ( Fig. 23 ).

Pupa: Antennal base coarsely rugose. Antennal horns bidentate ( Fig. 24 ). Pronotum coarsely rugose and without a median conical projection. Abdominal tergites with a single transverse row of spines ( Fig. 25 ).

Third instar larva: Length 4.2–4.8 mm (n= 6). Integument entirely covered with spicules. Antennae about two times longer than basal width. Spatula robust, with an anterior transversal lobe bearing four major teeth ( Fig. 25 ), sometimes with much smaller teeth between them. Spatula bears two lateral basal projections ( Fig. 26 ), apically almost meeting the outer edge of the transversal lobe. Two groups of three small setiform papillae present on each side of the spatula, between the lateral projections and the transversal lobe. Dorsal, pleural and terminal papillae bearing stout, conical setae. Terminal segment in dorsal view with five papillae on each side bearing conical setae ( Fig 27 ).

Etymology: The specific epithet derives from the Ranquel language, meaning “flower”, in reference to the location of the galls induced by this species.

Material examined: HOLOTYPE MALE: Argentina, La Pampa, Santa Rosa, Laguna Don Tomás, 2.vii.2009, de agallas en inflorescencias de Prosopis caldenia, J.J. Martínez col. ( MACN) PARATYPES, three males, three females, six larvae and one pupal exuvia, same data as holotype ( MACN)

Comments: Pupal description is based on a single pupal exuvia, it was not possible to observe the prothoracic spiracles due to the condition of the specimen.

Biological observations: Tetradiplosis rayen induces stem galls on the rachis of the developing inflorescences of P. caldenia causing complete flower and fruit abortion. The resulting gall is a lignified pedicelate fruit like structure ( Fig. 28 ) with a single central longitudinal chamber containing several cecidomyiid larvae ( Fig. 30 ). Adults emerge in spring from the previous year’s galls and probably oviposit on or near developing inflorescences. Immature larvae can be found inside the galls during spring and early summer. Mature larvae remain in the galls from late summer until the following spring, when adults emerge through a single subapical emergence hole ( Fig. 29 ). The life history strategy of T. rayen , cannot be clearly included in any of the types described by Yukawa and Rohfritsch (2007). The overwintering stage inside the gall is the third instar larva is similar to their definition of the type II A, but in Yukawa and Rohfritsch’s classification the development of the first instar larva seems to take more time compared with our observations on the development of T. rayen . The galls induced by T. rayen support a much simpler community than that of galls induced by T. panghitruz . An unidentified species of Torymidae is the only common parasitoid in this gall; additionally one braconid larva was collected while dissecting the galls, probably belonging to the genus Allorhogas . After the emergence of the adult cecidomyiids, some galls are occupied by Myrmelachista gallicola ( Hymenoptera : Formicidae ) (Quirán & Martínez 2008).

Figures

FIGURES 16 – 20. Tetradiplosis rayen. 16, head frontal; 17, male third antennal flagellomere; 18, female third flagellomere; 19, wing; 20, tarsal claw, empodium, and pulvillus of hind leg.

FIGURES 21 – 27. Tetradiplosis rayen. 21, male genitalia, dorsal; 22, abdomen of female, lateral; 23, female terminalia, lateral; 24, pupal antennal horns; 25, pupal abdominal tergites, lateral; 26, larval spatula and associated papillae, ventral; 27, larval terminal segments, dorsal.

FIGURES 28 – 30. 28 external morphology of galls induced by T. rayen; 29, detail of the subapical exit hole; 30, immature larvae of T. rayen inside the gall.