A new species of Brethesiamyia Maia (Diptera: Cecidomyiidae) from Colombia with description of immature forms

A new species of Brethesiamyia (Diptera: Cecidomyiidae) is described from Colombia, which represents the first record of the genus for the country. We described the species based on male, female, pupa, larva of third instar and gall morphology, which the larva induces on leaves of Myrcia sp. (Myrtaceae) from the foothills situated at the connection of the Andes and the Amazon basin from Colombia. The first description of the third larval instar is provided for the genus. Key-Words. Asphondyliini; Gall makers; Myrtaceae; Neotropical; Schizomyiina.


INTRODUCTION
The genus Brethesiamyia Maia belongs to Schizomyiina (Diptera, Cecidomyiidae), a subtribe with worldwide distribution, of which the largest richness is found in the neotropics, where 19 of the 28 valid genera are distributed endemically (Gagné & Jaschhof, 2017). Genera of Schizomyiina are characterized by the larva with ventral anus and the gonostylus tooth unfused (Tokuda, 2012). The only representative of the subtribe in Colombia is Schizomyia manihoti Tavares, associated with Manihot utilissima Pohl. (Euphorbiaceae). Brethesiamyia is a monotypic genus of cecidomyiid that induces leaf galls on Myrcia retorta Cambess (Myrtaceae) in Brazil (Maia et al., 2009). Larval forms of Brethesiamyia are unknown.
Myrcia is the fourth largest genus of Myrtaceae, containing around 800 species. Its distribution is exclusively Neotropical with the highest species diversity in the Amazon and the Caribbean but is even higher in the Brazilian Cerrado and the Atlantic forest biomes (Lucas et al., 2018). There are 392 known species in Brazil (Flora do Brasil 2020, 2020) and 28 in Colombia (Parra-O. et al., 2018). No one of the 45 species in 21 genera of gall maker insects distributed in Colombia was found inducing galls in species of Myrtaceae.
In this paper, we describe the second known species of the genus Brethesiamyia from the Neotropical region also galler in leaves of a Myrcia species, the first one from Colombia, as well as the first description of the third larval instar of the genus.
The branches with galls were placed into several labeled plastic bags and transferred to the laboratory. In the laboratory, some galls were maintained in the plastic bags until the emergence of the adults and some were dissected to obtain the immature forms. All specimens obtained from rearing were conserved in 80% alcohol for slide mounting. The study followed the adult morphology terminology of Gagné (2018) while the ISSN On-Line: 1807-0205 ISSN Printed: 0031-1049 ISNI: 0000-0004-0384-1825 immature terminology and the slide mounting method were based on Gagné (1994). Electron microscope images were taken with a FEI/THERMO Quanta 650 FEG available at Laboratório Nacional de Nanotecnologia (LNNano), in the Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas. The holotype was deposited in the Entomological Museum Universidad Nacional Agronomía Bogotá (UNAB) following the curatorial standards of Martínez-Alava & Serna (2015). The paratypes were deposited in the Diptera Collection of the Museu de Zoologia da Universidade de São Paulo (MZUSP). Type specimens of Brethesiamyia myrciae Maia from Museu Nacional do Rio de Janeiro (MNRJ) were examined for comparison. Diagnosis: Female flagellomeres 9-12 progressively shortened; female circumfila reticulate; palpus one-segmented; first tarsomeres without pointed ventroapical extension; empodia much shorter than claws; claws similar on all legs; tooth of gonostylus denticulate; parameres [= mesobasal lobes sensu Gagné, 2018] present; aedeagus bulbous; female abdominal tergite 8 without cercilike lobes; female abdominal segment 9 short, pliable, with long setae; pupal antennal horns short (Maia et al., 2009).

Taxonomy
Addition to the diagnosis: Pupal cephalic setae absent.

Remarks:
In the original description of Brethesiamyia, Maia et al. (2009) highlighted its similarities with the genera Stephomyia Tavares and Bruggmannia Tavares, although pointing out that Brethesiamyia have distinctive characters, especially on ovipositor. In Brethesiamyia, the ovipositor is longer than in Stephomyia, and the cerci are separated apically (Fig. 2D), whereas fused in Bruggmannia. The adults of all collected specimens of the new species of Brethesiamyia presented these distinctive characters. In B. myrciae, female antennal flagellomeres have circumfila incompletely reticulated, sternite 7 about 1.2 longer than the protrusible portion of ovipositor; cerci reniform and hypoproct deeply bilobed in males, pupa with antennal horn bifid; and induces tear-shaped gall. The adults of B. colombiana sp. nov. have flagellomeres completely reticulated in the female antennae, sternite 7 about twice longer than protrusible portion of ovipositor; cerci triangular and hypoproct weakly bilobed in males, and pupa with antennal horns triangular, single pointed and 4,25 longer than in B. myrciae; and induces cylindrical galls. Third larval instar is herein described for the first time, and the absence of cephalic setae was added to the diagnosis of the genus.

DISCUSSION
Both species of Brethesiamyia induce leaf galls on species of Myrcia, one of the richest plant genera of the Brazilian (Flora do Brasil 2020, 2020) and Colombian flora (Parra-O. et al., 2018). Based on the morphological characters of the host plant of B. colombiana sp. nov., it can be regarded as belonging to the genus Myrcia, probably M. canalicula-   (Sobral et al., 2010). The disjunction of the distribution observed for the Brethesiamyia species along with the wide distribution of the genus of the host plant in Neotropical region, particularly in South America, suggests that the genus could be much more diverse and present in different types of biomes in the Neotropical Region than it was previously known.