Sennius ricardo, Viana & Ribeiro-Costa, 2013

Viana, Jéssica Herzog & Ribeiro-Costa, Cibele Stramare, 2013, Bruchines (Coleoptera: Chrysomelidae) associated with Senna neglecta (Vogel) H. S. Irwin and Barneby (Fabaceae: Caesalpinioideae): a new host plant for the subfamily, Journal of Natural History 48 (1 - 2), pp. 57-85 : 79-82

Sennius ricardo sp. nov.

( Figure 6 A–H)

Description

Dimension. Length (Pronotum-elytra) 2.44 mm. Width 1.60 mm.

Integument colour. Head, thorax and elytra black, elytron sometimes with transverse irregular dark brown macula in submedian region ( Figure 6A ) that extends from the third to eighth striae interval. Abdomen and pygidium dark brown to black ( Figure 6B, D ). Antennae, hind legs, maxillary and labial palps dark brown ( Figure 6B, C ). Fore and middle legs red-orange to dark brown ( Figure 6B ).

Pubescence. Head with dense tuft of white hair posterior to the postocular lobe, white pubescence moderately dense in the ocular sinus, postocular lobe and mandible ( Figure 6C ). Labrum with scattered golden pubescence, denser at apex ( Figure 6C ). Pronotum with sparse white and golden pubescence; white pubescence moderately dense at posterior corners and in antescutellar area, sometimes at anterior corners ( Figure 6A ). Scutellum with dense white pubescence ( Figure 6A ). Elytron with mix of black, white and golden pubescence, dense white pubescence distributed as follows: in small tufts at base of thirrd, fifth and sixth striae intervals; in submedian irregular transverse macula extending from first to ninth striae intervals, generally covering the macula with a dark brown integument ( Figure 6A ). Pygidium with sparse pubescence on anterior half, and with moderately dense white pubescence and dense median line on posterior half ( Figure 6D ). Ventral region of body with white pubescence, denser at base of mesepimeron, metepisternum, metasternum, distal region of posterior coxa, and base of first abdominal ventrite ( Figure 6B ).

Head evenly punctuate, except at midline of frons, base of clypeus and labrum; frons convex, frontal carina and transverse sulcus absent; ocular sinus deep, more than half an eye length ( Figure 6C ). First and third antenna segments filiform, second and fourth moniliform, fifth to tenth broader than long, eleventh globular and pointed at apex ( Figure 6B ). Pronotum moderately convex, disc sulcate at basal lobe ( Figure 6A ). Scutellum subquadrate, slightly wider than long ( Figure 6A ). Base of elytra without denticles at striae. Hind femur with a very prominent tooth (0.05 mm), microserrate on ventral margin near apex ( Figure 6E ). Hind tibia with lateroventral carina extending more than half its length ( Figure 6F ); lateral, dorsomesal and ventral carinae long, ending near coronal denticles ( Figure 6E, F ); mucro slightly larger than the opposite coronal denticle ( Figure 6E, F ). Last abdominal ventrite of male emarginate at middle, rounded in female. Pygidium not concealed by elytra, lateral margins slightly curved, rounded apex in male, more acuminate in female ( Figure 6B, D ).

Male genitalia. Median lobe about 4.3 times longer than its width at middle, not expanded at apex; ventral valve triangular with lateral margins straight and slightly rounded at apex; hinge sclerites of median lobe short; internal sac at basal region without spicules near base of ventral valve, submedian region with dense cluster of short spicules evenly distributed, apparently forming two more sclerotized longitudinal masses; subapical region with denticles and tiny microserrate sclerites; spicules slightly larger than those of submedian region and slightly denser than at lateral lobes of internal sac ( Figure 6G ). Tegmen with lateral lobes separated by deep emargination, about 0.7 times the length of lateral lobes ( Figure 6H ).

Type material

Holotype and allotype deposited in DZUP, with label: “ Brasil, RJ-Teresópolis | P.N. Serra dos Órgãos | 22 / VIII / 2006 | J.H. Viana col.” “Em | Senna neglecta | var. oligophylla ”. One paratype deposited in MNRJ, with label: “ Brasil, RJ-Teresópolis | P.N. Serra dos Órgãos | 12 / VIII / 2007 | J.H. Viana col.” “Em | Senna neglecta | var. oligophylla ”. One paratype deposited in MZSP, with label: “ Brasil, RJ-Teresópolis | P.N. Serra dos Órgãos | 16 / VI / 2006 | J.H. Viana col.” “Em | Senna neglecta | var. oligophylla ” .

Distribution

Brazil (Rio de Janeiro).

Host plant

Fabaceae : Caesalpinioideae : Senna neglecta var. oligophylla .

Discussion

Sennius ricardo sp. nov. differs mainly by having pronotum with dense white pubescence on posterior corners and antescutellar area, as well as small tufts at base of third, fifth and sixth striae intervals of the elytron ( Figure 6A ), hind femur with very prominent microserrate tooth ( Figure 6E ), and hind tibia with lateroventral carina longer than half its length ( Figure 6F ). In terms of the male genitalia, the hinge sclerites are short, and the internal sac has denticles and is microserrate, with tiny sclerites at the subapical region and spicules slightly larger than those of submedian region and slightly denser than those of the lateral lobes ( Figure 6G ).

As in the previous species, Sennius ricardo sp. nov. shows a pattern of male genitalia similar to that found in species of subgroup 2 of the fallax group of Sennius . It is similar to Sennius atripectus by its male genitalia pattern, but in Sennius ricardo sp. nov. the basal region has no spicules near the base of the valve (present in Sennius atripectus ) and hinge sclerites are more curved in this species and less curved in Sennius atripectus .

Etymology

The specific name “ricardo” is in honour of Professor Ricardo Ferreira Monteiro, for his great professional and personal contribution to instructing J.H. Viana. This is a noun in apposition, gender masculine.

Final considerations

There have been only two previous papers from Brazil focusing on bruchines associated with host plants that provided identification keys and species illustrations, including male genitalia – one on the beetles hosted by Senna multijulga and the other on Chamaecrista species ( Ribeiro-Costa and Reynaud 1998; Silva et al. 2003). We focused on Senna neglecta in this paper, and for the first time recorded it as a host for six species of Bruchinae , three of them new from three associated genera. Five species belonged to Bruchini , the largest tribe in the subfamily (with 80% of the known species); only one species belonged to Amblycerini , also a very diverse tribe. Among the species of Bruchini , Acanthoscelides multimaculatus sp. nov. is allocated to the group quadridentatus of Acanthoscelides that now comprises 16 species. Sennius bondari and Sennius nappi , also of Bruchini , were placed in the abbreviatus group, increasing the number of species in this group to nine. Sennius margarete sp. nov. and Sennius . ricardo sp. nov. were included here in the fallax group, subgroup 2, which now has eight species.

Only one species of Acanthoscelides and one of Amblycerus , the richest genera of Bruchinae , were recorded consuming S. neglecta seeds ( Acanthoscelides multimaculatus sp. nov. and Amblycerus hoffmanseggi ). Sennius had the highest number of species feeding on this host – four species; two of them are described here, resulting in a total of 59 species now assigned to this genus. A possible explanation for this high number of Sennius species associated with Senna neglecta is the special preference of this genus for Cassiinae hosts, particularly Senna . Among all of the species recorded in association with Senna neglecta , Sennius bondari is the most polyphagous, for it has been found associated with a total of 11 Senna species (and even one different plant family).

The interactions between bruchines and their host plants are subject to variables such as temporal, seasonal and spatial changes, parasitism and competition, making it unlikely to find all of these seed predator species at the same time in the same place ( Romero et al. 2009). Long-term studies with many types of fruits and seeds throughout the different host plants’ reproductive cycles will be necessary to gather complete records of all host associations and to survey all the species in specific localities.

Figures

Figure 6. Sennius ricardo sp. nov. (A) Dorsal view; (B) lateral view; (C) head, frontal view; (D) pygidium; (E) part of hind leg, internal view; (F) hind tibia, external view; (G, H) male genitalia: (G) median lobe with hinge sclerites and others sclerites in internal sac magnified; (H) lateral lobes.