Thyreocephalus

Márquez, Juan & Asiain, Julieta, 2016, Taxonomy of the Mexican species of Thyreocephalus Guérin-Méneville (Coleoptera: Staphylinidae, Xantholinini), Zootaxa 4169 (2), pp. 251-285 : 258-260

Thyreocephalus sp. aff. subtilis Sharp, 1885

(Figs. 1c, d, 5b, 6b, 7c, d, 9b, 11b, 13a)

Total body length 16.5–18.7 mm. Body glossy black, except that elytra have a fine metallic blue tint ( Fig. 7 ), maxillary and labial palps, and prosternum reddish; antennomeres 4–11 gray.

Head oval shaped, with convex lateral borders and posterior corners (Figs. 1c, 7c, d); head slightly convex in lateral view; almost as long as wide (proportion length/width 1.07); wider than pronotum (1.3 times). Dorsal surface with fine and umbilicate punctures, dense fine punctures on the front and at center of head, and umbilicate punctures denser behind eyes, at lateral areas and their continuation with ventral surface (Fig. 1c). Umbilicate punctures on ventral surface are combined with roughness at lateral and posterior areas, becoming sparse at center and fine punctures are denser (Fig. 1d). Eye 0.23 times as long as head. First antennomere 1.8 times the length of second and third antennomeres combined, third antennomere 1.5 times the length of second, fourth and fifth almost quadrate, antennomeres 6 to 10 slightly transverse. Labrum with two pairs of acute teeth, the central pair biggest ( Fig. 5 b). Mandibles 0.66 times as long as the head, slender and teeth similar as in T. unicolor . Neck with a long sunken area, shallow and long shaped (Fig. 1c).

Pronotum almost as long as head, slightly wider at anterior corners than posterior corners; with punctures as in remaining species (Fig. 1c). Scutellum with 5–6 fine punctures and microsculpture as wavy lines. Elytra 1.1 times the length of pronotum; with faint blue metallic reflection that is best appraised when the specimen is moved under light; with very dense punctation almost homogeneously distributed, except in the smooth belt parallel to the lateral border.

Prosternal sclerite reddish, divided by a fine longitudinal midline. Prosternum only with intercoxal process, without posteromedian carina, but this area is slightly inflated ( Fig. 6 b). Mesosternum without impressed midline that divide it in two half. Metasternum similar to remaining species.

Abdomen glossy, with microsculpture as wavy lines; first four visible tergites with a sunken area parallel to the anterior border. Male genital sternite similar to remaining species. Aedeagus median size (length 1.4 mm), oval longer shaped, notably narrowing to the apex; apical area of median lobe 0.26 times their total length, narrow at their anterior third; symmetrical parameres, slender, narrowing toward apex, 0.34 times as long as median lobe; internal sac poorly visible, narrow, occupying almost 2/3 of length of median lobe, microsculpture not visible ( Figs. 9 b, 11b).

Variation. The only studied male has the head wider and more rounded than females, with a proportion length/ width 1.0; whereas in females (n= 5) the proportion is 1.08 to 1.14 times ( Figs. 7 c, d). Similarly, the male has a head 1.45 times longer than the pronotum and in females the head is 1.23 to 1.34 times longer than pronotum. The ventral surface of the head has variation in the umbilicate punctures combined with roughness, from only umbilicate punctures (without roughness) to an area with rough striations.

Diagnosis. Thyreocephalus sp. aff. subtilis can be confused mainly with T. unicolor . Their differences were commented on in the diagnoses of T. unicolor . In addition, Sharp (1885) comments that T. subtilis is similar to T. salvini , known from Panama, for the similar color pattern of the body and the wide head in males. The Mexican species was tentatively identified as near to T. subtilis , due to the lack of the study of the type series. This species can be distinguished from T. salvini by the faint metallic blue reflection on the elytra and dense punctation almost homogeneously distributed, head with less density of dorsal umbilicate punctures, and the head not more than 1.45 times wider than pronotum. Whereas in T. salvini the elytra are evidently metallic blue, with sparse, rough punctation, irregularly distributed, head with dorsal umbilicate punctures very dense behind the frontal cavities, laterally and on the vertex, and the width of the head reaches twice the width of the pronotum ( Sharp 1885).

Discussion. The identification of this species was difficult without the study of the types of the species from Central and South America. It was made using photographs, that are an alternative when it is difficult to borrow and study the type specimens ( Fig. 7 ). Due to the above, this Mexican species was identified as near to T. subtilis , until it is compared with the type specimens. Also, it is possible that a future analysis that includes the species missing in this work will show that this is a different species than T. subtilis (new or known).

Natural history. It is interesting that this species has been collected in urban areas near to Xalapa city, Veracruz, as well as in surrounding places in coffee plantations, a situation that probably denotes the ecological plasticity of the species to search for potential prey and inhabit these kinds of environments.

Distribution ( Fig. 13 a). At the moment, T. sp. aff. subtilis is recorded only from Mexico (state of Veracruz), whereas T. subtilis is recorded from the Antilles, Brazil, Colombia, Panama, Peru and Venezuela ( Herman 2001, Asenjo 2004, Newton et al. 2005, Asenjo et al. 2013).

Material examined. " Mexico: Veracruz, Xalapa, Avenida Murillo Vidal, en suelo, junio-julio-2000, Q.

Santiago col." (1 ♂, 2 ♀, MUZ-UV)." Mexico : Veracruz, Xalapa, Colonia Pomona , directa en casa, III-2 0 15, L. Delgado col." (1♀, IEXA) ; same data as previous, except: "VI-IX-2010" (1♀, IEXA); " Mexico : Veracruz, Coatepec, La Pitaya , N 19° 29´28", W 96° 56´59", selva mediana subcaducifolia, 1245 m, en suelo, 12-VII-2000, J. Asiain, Q. Santiago y J. Márquez cols." (1♀, MZFC) ; "Mexico: Veracruz, Tlalnelhuayocan, Rancho Viejo, Agüita Fría , bajo rocas de río, 08-IV-2000, E. Montes de Oca col." (1♀, MUZ-UV).

Additionally we analyzed photographs of one syntype of T. subtilis from Chiriquí Volcano in Panama provided by R. Booth from The Natural History Museum, as well as a photograph of a non-type specimen from Peru (without more data) provided by L. Herman from the American Museum of Natural History ( Fig. 7 ).

Figures

FIGURE 5. Dorsal view of the labrum of: a) Thyreocephalus unicolor, b) T. sp. aff. subtilis, c) T. jalapaensis, d) T. scutellaris, e) T. puncticeps, g) T. rufipennis, h) T. halffteri, i) T. arizonicus.

FIGURE 6. Ventral view of the pronotum showing the posteromedian carina (lacking in b) and the postcoxal process in: a) Thyreocephalus puncticeps, b) T. sp. aff. subtilis. Lateral view of the pronotum showing the develop and variation of the posteromedian carina in: c) T. puncticeps, d) T. arizonicus, e) T. scutellaris, f) T. jalapaensis, g) T. unicolor.

FIGURE 7. Photographs of: Thyreocephalus subtilis, a) syntype mounted on a plate with label data (provided by BMNH), b) close-up of the same syntype specimen (BMNH). Thyreocephalus sp. aff. subtilis, c) male specimen studied (Xalapa, Veracruz), d) female specimen studied (Xalapa, Veracruz), e) specimen of T. subtilis from Peru (not studied, only photo; AMNH). Scale = 5 mm.

FIGURE 9. Ventral view of the aedeagus of: a) Thyreocephalus unicolor, b) T. sp. aff. subtilis, c) T. jalapaensis, d) T. scutellaris, e) T. cribripennis, f) T. rufipennis, g) T. halffteri. Scale = 0.5 mm.

FIGURE 13. Geographic distribution and individual track of: a) T. sp. aff. subtilis (black square) and T. scutellaris (gray circles); b) T. cribripennis (black circle) and T. halffteri (gray squares).