Rustitermes Constantini, Castro & Scheffrahn, 2020

Castro, Daniel, Constantini, Joice P., Scheffrahn, Rudolf H., Carrijo, Tiago F. & Cancello, Eliana M., 2020, Rustitermes boteroi, a new genus and species of soldierless termites (Blattodea, Isoptera, Apicotermitinae) from South America, ZooKeys 922, pp. 35-49 : 35

Rustitermes Constantini, Castro & Scheffrahn gen. nov.

Type species.

Rustitermes boteroi sp. nov.

Diagnosis.

Enteric valve with six slightly asymmetrical cushions. Each cushion forming a central pouch made of scales smaller than those between the cushions. Each cushion composed of about 60-80 scales, wider at the base and narrower at the apex. Posterior portion of pads truncated, with 35 to 50 rectangular scales arranged from the middle to the apex of the cushion and increasing in density in this same direction.

Imago (Fig. 1 ; Table 1 ). Fontanelle inconspicuous in both sexes, the region of the fontanelle depressed; medium spot slightly conspicuous. Left mandible with apical tooth a little bit larger than M1 + 2; M3 triangular with lateral margins forming an obtuse angle; non-conspicuous premolar process; molar process not hidden by molar prominence (Fig. 2C ).

Head capsule with short, sparse bristles; coloration of head capsule dark brown; frontal marks slightly lighter than rest of head capsule, with poorly defined margins. Pronotum subhexagonal, with anterior margin straight, without central incision; lateral margins very straight and well-marked; pronotum with few sparse bristles and short hairs. Tergites and sternites with short hairs covering the plates. Fore coxa with a set of 4-5 prominent long bristles; inner face of fore tibia with two rows of 6-7 thick bristles.

Worker (Figs 2 - 4 ). Monomorphic. Small and rounded fontanelle; postclypeus rather slightly inflated; head capsule covered with medium and long bristles. Left mandible with prominent apical tooth compared to M1 + 2, triangular M3 with lateral margins forming a right/acute angle, molar process not concealed by molar prominence. Pronotum with long bristles, concentrated along margin of anterior and posterior lobes. Tergites and sternites with dense cover of long bristles, facing the posterior region or upwards. Fore coxa with a set of 4-5 thick bristles; inner face of fore femur with long bristles. Fore tibia moderately inflated, inner face of fore tibia with two rows of 6-7 thick bristles.

Mixed segment (MS) separated from ileum (P1) by a simple transverse junction; P1 of uniform width along entire length, forming an inverted C in ventral view. Enteric valve without armature, with six pyriform cushions of slightly different dimensions, the two largest and two smallest cushions adjacent to each other. The center of each cushion is formed into a lumen-facing pouch consisting of about 60 fringed scales. The remainder of the cushions consists of 50-75 (depending on size of cushion) larger fringed polygons. The cuticle between the cushions is composed of even larger fringed cuboidal scales. All cushions are wider at base (near P1) and narrower at apex (near P3). Tubular and short EV seating. Worker measurements highly variable among and within different colonies (Table 2 ).

Comparison and remarks.

The digestive tube coiling of the new genus is similar to Hydrecotermes , but R. boteroi sp. nov. can be differentiated by the worker, which has thick bristles along the inner margin of the fore tibia, absent in Hydrecotermes . In the workers, the enteric valve and the digestive tube may be similar to Aparatermes , but the cuticle between the cushions in Aparatermes does not have cuboidal scales. In Aparatermes the insertion of P1 in P3 occurs in dorsal view with a trilobate EV setting, in Rustitermes the enteric valve seating (EVS) is not trilobate. Also, the enteric valve of Aparatermes has small spines or pointy scales, which are absent in R. boteroi sp. nov.; in addition, the EV in Aparatermes has the posterior portion of the pads without scales. The imago presents a visible molar process and fore tibia with two rows of thick bristles.

Molecular analysis.

The Bayesian phylogeny using the COI marker clearly separates Rustitermes gen. nov. from the other soldierless termites (Figure 5 ). The new genus was recovered as sister group of Patawatermes , but without high posterior probability support.

Etymology.

Named in honor of Michael K. Rust, retired professor of urban entomology at the University of California, Riverside (UCR), and mentor of RHS. Mike encouraged RHS to publish his first taxonomic paper ( Scheffrahn and Rust 1983).

Figures

Figure 1. Female imago head capsule, pronotum and fore leg of Rustitermes boteroi sp. nov. A dorsal view B lateral view. Specimen from lot MZUSP 26677. Scale bars: 0.5 mm.

Figure 2. Rustitermes boteroi sp. nov. A, B worker head capsule in dorsal and lateral view C imago mandibles D worker mandibles E worker right fore tibia F live habitus of worker. MP = molar process. Specimens from lot CATAC 1797 (A, B), MZUSP 26677 (C, D), BO 437 (E).

Figure 4. Worker enteric valve of Rustitermes boteroi sp. nov. A EV fully stretched laterally, showing the six cushions (end cushion bisected) B EV detail of smallest cushion in A C whole mount EV lateral profile of cushions. Food flow in each image from bottom to top.

Figure 5. Bayesian phylogenetic tree of the Apicotermitinae subfamily using the COI region. In red, Rustitermes boteroi gen. et sp. nov. Branch support is posterior probability.