Fonsechellus Silvestri, 1946

Zilberman, Bruno & Fontes, Luiz Roberto, 2020, New species and morphological notes on the termitophilous genera Fonsechellus Silvestri and Oecidiophilus Silvestri from Brazil (Staphylinidae, Aleocharinae, Corotocini, Termitoceina), Papéis Avulsos de Zoologia (Pap. Avulsos Zool., S. Paulo) 60 (21), pp. 1-13 : 2-3

Fonsechellus Silvestri, 1946

Fonsechellus Silvestri,1946:312 .Typespecies: Fonsechellus diversicolor Silvestri , by original designation.

Trianellus Silvestri, 1946: 315 (subgenus); Seevers, 1957: 130 (suggested synonym); Kistner, 1993: 201 (synonym). Type species: Fonsechellus (Trianellus) bicolor Silvestri , by monotypy.

Diagnosis: Physogastric and small species, usually less than 2 mm long, sclerotized parts reddish‑brown to pale yellow, paratergites separated and barely sclerotized. Tarsal formula 5‑5‑5, two spurs at apex of anterior tibia and one at apex of median tibia. Tergites sclerotized into rectangular bands and sternites poorly sclerotized, and sides of third or fourth to sixth sternites with dense clusters of bristles, geniculate in some species. Chaetotaxy of pronotum and abdomen with interspecific variation in size and density; also variable between male and female in some species.

Redescription: Head slightly longer than wide, widest right before the eyes; gula straight; foramen magnum less than 2.5 times the head width; eyes circular in shape; front impressed; antenna with 11 antennomeres: scape elongate, antennomeres II‑X subquadrate, XI oblong, with proximal margin transverse. Mentum fused to submentum (postmentum), subtrapezoidal, lateral margins evenly round; position of the three main bristles near apex variable interspecifically. Prementum subquad‑ rate, labial palpi with 3 palpomeres, ligula broad, bilobed apically in most species. Mandibles asymmetrical; right mandible with longitudinal row of small teeth on cutting edge; both mandibles bear a median tooth, conspicuously larger on left mandible, and a drop‑shaped sulcus on lateral margin. Maxillae with stipites longer than wide, each bearing three long bristles: two on posterior region on either side next to cardo, and another next to the palpifer; galea about as long as lacinia, subquadrate with many short bristles; palpi with 4 palpomeres, first palpomere small, subquadrate; second palpomere elongate and about three times longer than the second; third palpomere slightly longer than the second; fourth narrow, about twice as long as the first. Labrum transverse in most species, with p1, m2‑m1 and at least one bristle of d row present; most species with conspicuous pairs of median rows of bristles.

Thorax: Pronotum about as long as wide, widest on anterior margin, which is slightly convex; chaetotaxy variable. Wings present and broken. Elytra setose, about 1.5 times longer than wide and lateral margins straight in most species. Mesosternum slightly shorter and narrower than metasternum; endosternite with slender arms,about 1.5 times longer than the base. Legs well developed; anterior tibia with two internal apical spurs and median tibia with one.

Abdomen highly physogastric with generalized pattern shape; segment I with a narrow tergite with medial margin projected backwards; segment II with one tergite and paratergites, the latter as sclerotized diagonal bands; paratergites of remaining segments barely sclerotized. Segments III‑VIII each with complete tergite and sternite; tergites expanded posteriorly with secondary sclerotization; sternites represented by weakly sclerotized bands, sometimes barely visible; rows of bristles present on tergites and sternites, with length varying between species or even between male and female within a same species; sternite VIII wider than long, with six main bristles: a row of four bristles on median region and another row with two; the distance between the two rows vary between male and female, being closer in the latter; tergite VIII subquadrate, with two pairs of long bristles on median region (a2‑a1), three to four pairs of medium‑sized bristles present apically (p3‑p2‑p1/ p4‑p3‑p2‑p1); distance of each side a1 bristle vary between male and female, being closer on the latter; sternite IX in females divided into two slender pieces attached to margins of tergite IX; sternite IX in males in one piece shovel‑shaped apically and variable chaetotaxy among species; tergite IX with long apodemes in males and many small‑medium size bristles; a distinct long bristle is present in most species; tergite X subquadrate with chaetotaxy variable, two pairs of long bristles on either side and a central bristle of same size is a condition present in most species. Aedeagus bulbous with shape of median lobe apex variable in some species. Spermatheca with capsule and stem sclerotized, shaped similarly among species.

Host relationship: Fonsechellus species were found living in association with one the following termite genera or species: Velocitermes Holmgren , Diversitermes Holmgren , Subulitermes Holmgren , Atlantitermes guarinim Fontes, 1979 , and Araujotermes caissara Fontes, 1982 .

Remarks: Fonsechellus species are often compared to those of Termitoiceus ( Silvestri,1901; Seevers,1957; Kistner, 1993) due to overall body shape. Silvestri (1901) distinguished members of Fonsechellus in having a bilobed ligula, macrosetae on tergite IX and geniculate setae on sternites IV‑VII. Additional differences from Termitoiceus pointed out by Kistner (1993) are related to the shapes of the labial palps, pronotum, elytra, meso‑ and metasternum, meso‑ and metanotum, mandibular teeth, galea, tarsi, and sclerotization of tergites and paratergites, as well as the shape of lateral lobe of aedeagus and connection of gland reservoir of abdominal segment VII.

The degree of sclerotization of tergites, sternites and parategites,mildin Fonsechellus andheavyin Termitoiceus , is probably the most conspicuous difference at first glance. Some species of Fonsechellus do not have geniculate bristles on sternites, bilobed ligula or macrosetae on tergite IX. The presence of mandibular sulcus on lateral margin,longitudinal row of small teeth present near apex of right mandible, sexual dimorphism of chaetotaxy (a1 bristles) of tergite VIII,and shovel‑shaped apex of sternite IX (male), could be considered as generic characteristics, but a broader study of other genera in Termitoceina is needed for confirmation. Other characteristics present in most species (except F. fontesi , discussed later in this paper) are bilobed ligula, distinct macrosetae on tergite IX and conservative chaetotaxy for tergite X.