Tetradiplosis Kieffer & Jörgensen

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 : 588-591

Genus Tetradiplosis Kieffer & Jörgensen

Tetradiplosis Kieffer & Jörgensen 1910: 421 ; Gagné 1994: 169, catalog of Neotropical species; Gagné 2010: 390, catalog of World species.

Type species: Tetradiplosis sexdentata Kieffer & Jörgensen , by monotypy

The genus was described based on the female, pupa and larva ( Kieffer and Jörgensen 1910; syntype series presumed lost, Gagné 1994), and the male was described later by Gagné (1994). It is characterized by the following characters: wing venation with vein R5 joining C beyond wing apex, Rs weak but evident and beyond midlength of R1, base of M slightly curved, and M3 fold present; male flagellomeres with first and third circumfila with long loops, contrasting with the much shorter loops of the second circumfilum; tarsal claws with two teeth, the basal one smaller; female cerci elongate-ovoid, with closely set setae apicoventrally; pupa with pointed antennal horns, sometimes with a conical prothorax which projects beyond them, with or without spines on abdominal terga; larva with a robust spatula bearing 4–6 teeth anteriorly.

Comments: The new species of Tetradiplosis broaden the concept of the genus compared with the original description and the definition provided by Gagné (1994). Kieffer & Jörgensen stated that the type species of the genus has a four segmented palpus, whereas Gagné (1994), based on specimens of undescribed species, stated that Tetradiplosis has a three segmented palpus. The study of both the original description, the specimens collected and studied by Gagné in northern Argentina, and the new species described herein, allows us to conclude that Tetradiplosis has a variable number (3–4) of palpal segments. The larval and pupal morphology also exhibits considerable variation (see discussion below).

Tetradiplosis panghitruz Martínez , new species ( Figs 1–11 )

Adult: Body length 3.2–4.1 mm (n= 20)

Head: Eyes large, widely connate ( Fig. 1 ), eye bridge about 8–9 facets long, facets hexagonal, closely adjacent throughout. Occiput with a distinct dorsal protuberance. Frons with 3–5 setae per side. Palpus four segmented. Labella evenly convex in frontal view, each with 6–8 lateral setae. Male third flagellomere ( Fig. 2 ) binodal, with three circumfila, first and third circumfila loops distinctly long, second circumfilum loops much shorter. Female third flagellomere ( Fig. 3 ) cylindrical, 2.7–2.8 times longer than its median width, with two appressed circumfila

Thorax: Wing length, male 2.5–2.6 mm (n= 5); female 3.0– 3.3 mm (n= 16). Wing veins M3, Cu1 and Cu2 faint apically ( Fig. 4 ). Anepimeron with 20–24 setae. Acropods with claws bent before middle length and bidentate ( Fig. 5 ). Empodium as long as bend in claw or slightly longer. Pulvilli about half as long as empodium.

Male abdomen: Tergites 1–6 rectangular with an irregular row of setae apically and a few setae laterally; tergites 7 and 8 much shorter, irregular in shape, and mostly devoid of vestiture (similar to tergite 8 in figure 6). All tergites with a pair of anterior trichoid sensillae. Sternites 2–7 rectangular. Genitalia ( Fig. 6 ): 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 rugose on outer surface and somewhat slender, wider basally and slightly constricted in the middle, setose on outer surface and on inner surface near gonostylus. Gonostylus elongate and slightly bumped basally, setulae almost reaching half the length of the gonostylus.

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

Pupa: Each antennal base with a small and acute antennal horn ( Fig. 9 ). Pronotum largely smooth without a median tooth-like projection. Abdominal tergites bare apically.

Third instar larva: Length 4.2–4.9 mm (n= 11). Integument mostly covered with spicules. Antennae about two times longer than basal width. Spatula robust, with two well developed anterior lobes, each bearing a pair of teeth, and an additional median basal tooth between lobes ( Fig. 10 ). In some specimens the median tooth is poorly developed or entirely missing, thus the spatula can be 5-toothed or rarely 4-toothed. Two groups of three small setiform papillae present on each side of the spatula. Dorsal, pleural and terminal papillae bearing a stout, conical seta. Terminal segment with four papillae bearing conical setae on each side in dorsal view ( Fig. 11 ).

Etymology: The new species is named after Panghitruz Güor (ca. 1820–1877), a leader of the Ranquel people, inhabitants of the caldén forests of central Argentina.

Material examined: HOLOTYPE MALE: Argentina, La Pampa, Santa Rosa, Laguna Don Tomás, 27.xii.2010 de agallas caulinares en Prosopis caldenia, J.J. Martínez col. ( MACN) PARATYPES, four males, 16 females and three pupal exuviae, same data as holotype ( MACN); two larvae, Argentina, La Pampa, Santa Rosa, Inti Hué, 18.i.2009, Martínez col. ( MACN); nine larvae, Argentina, La Pampa, Santa Rosa, Facultad de Agronomía, 5.i.2010, J.J. Martínez col. ( MACN).

Comments: The pupal morphology was described based on three pupal exuviae, the prothoracic spiracles were not observed due to the condition of the specimens.

Biological observations: Tetradiplosis panghitruz induces multilocular stem galls (larvae in individual chambers) on young stems of Prosopis caldenia ( Figs 12, 13 ) similar to those of other Tetradiplosis induced galls on other Prosopis species ( Kieffer & Jörgensen 1910; Jörgensen 1916, 1917; Gagné 1994). The abnormal tissue is induced in the xylem of one year old stems ( Fig. 14 ). In December the first mature larvae can be observed ( Fig.15 ) and in late December pupae are present inside the galls, and the first adults begin to emerge. Most adults emerge during January, although a few mature larvae can be found in the galls in late summer. Apparently, T. panghitruz has one generation per year. Our preliminary observations indicate that adults oviposit on developing stems in which immature larvae can be observed at the end of the summer, although at this point galls are barely recognizable as very subtle swellings on young stems. The first instar larva spends autumn and winter inside small longitudinal chambers, remaining largely inactive until the following spring, when galls become fully developed. According to the classification provided by Yukawa and Rohfritsch (2007), the life history strategy of T. panghitruz would fit in type II B, with the first instar larva as the overwintering stage. Galls induced by T. panghitruz support a complex community of parasitoids and inquilines of at least nine arthropod species including: an unidentified inquiline species of Contarinia Rondani ( Diptera : Cecidomyiidae ), three species of Allorhogas Gahan ( Hymenoptera : Braconidae ), one undescribed species of Percnobracon Kieffer & Jörgensen ( Hymenoptera : Braconidae ), one unidentified species of Torymidae (Hymenoptera) , one species of Eupelmidae (Hymenoptera) , one species of Sycophila Walker ( Hymenoptera : Eurytomidae ) and one species of Apion Herbst ( Coleoptera : Brentidae ). Additionally, abandoned galls are frequently occupied by Myrmelachista gallícola Mayr ( Hymenoptera : Formicidae ).

Figures

FIGURES 1 – 5. Tetradiplosis panghitruz. 1, head frontal; 2, male third antennal flagellomere; 3, female third flagellomere; 4, wing; 5, tarsal claw, empodium, and pulvillus of hind leg.

FIGURES 6 – 11. Tetradiplosis panghitruz. 6, male genitalia, dorsal 7, abdomen of female, lateral; 8, female terminalia, lateral; 9, pupal antennal horns; 10, larval spatula and associated papillae, ventral; 11, larval terminal segments, dorsal.

FIGURES 12 – 15. 12, Prosopis caldenia; 13, external morphology of galls induced by T. panghitruz; 14 longitudinal and transversal sections of galls induced by T. panghitruz; 15, mature larva of T. panghitruz inside the gall.