Xestotrachelus robustus ( Bruner, 1911 )

Silva, Daniela Santos Martins, Pereira, Marcelo Ribeiro & Lima, Raysa Martins, 2021, How to distinguish the Xestotrachelus Bruner, 1913 (Orthoptera: Romaleidae: Romaleini) from other Romaleini in South America, with a report of the first record in Minas Gerais, Brazil, Insecta Mundi 2021 (873), pp. 1-9 : 2-7

Xestotrachelus robustus ( Bruner, 1911) ( Fig. 1–2 )

Minas Gerais (new state record), Uberlândia, Panga Ecological Reserve (19°09′20″– 19°11′10″S and 48°23′20″– 48°24′35″ W) ; i-2009; Silva, D.S.M. leg; 1 ♀ and 1 ♂ pinned ( LACTA; code SILVA DSM106 and SILVA DSM107 ) .

Measurements. Female (bd: 40 mm, pr: 9 mm, t: 27 mm, hf: 15 mm, ht: 16 mm) and male (bd: 22 mm, pr: 6 mm, t: 16 mm, hf: 12 mm, ht: 14 mm).

Identification. Head, pronotum, and other parts of body are dark and marked with black, pale olive-yellow, and red; the red and black pattern of hind wings closely resembles red-winged species of Chromacris , however the head and thorax are much more robust; tegmina can be shorter, as long as or longer than the hind femur; hind tibiae are usually red ( Roberts and Carbonell 1982); abdomen has red punctuations on the dorsal, lateral, and ventral regions, hind femora and tibiae possess no bands ( Fig. 1–2 ). Phallic structures are similar to those in Chromacris but differing by the aedeagal valves being strongly sclerotized and larger; rami of cingulum narrow and epiphallus with ancorae well developed ( Roberts and Carbonell 1982).

Remarks. The tribe Romaleini is characterized by grasshoppers marked by large size and color polymorphism. There are some details about Xestotrachelus that allow their distinction from the other Romaleini grasshoppers found in South America:

Key to the South America Romaleini (only external morphology without genitalia)

1. Pronotum crestate, strongly arched......................................................... 2

— Pronotum without crest or poorly developed, not arched...................................... 5

2(1). Prozona crest with tree lobes fully developed................................................ 3

— Prozona crest without lobe................................................................. 4

3(2). Hind tibiae with spines of internal margin shorter, as a whole not surpassing in length those of external margin....................................................... Thrasyderes Bolívar, 1881

— Hind tibiae with spines of internal margin longer, most of them surpassing in length those of external margin........................................................ Aplatacris Scudder, 1875

4(2). Lateral carina of pronotum well-marked; median carina with the same color of the body; tegmina short, not extending beyond the middle of the second or third abdominal segment........................................................................... Eidalcamenes Rosas Costa, 1957

— Lateral carina of pronotum not well-marked; median carina with a different color than the body; tegmina long, extending past the abdominal segments.................. Callonotacris Rehn, 1909

5(1). Hind wings with red, orange, yellow, and black patterns...................................... 14

— Hind wings with other patterns............................................................ 6

6(5). Hind tibia with prominent spines (some almost in the same length of third hind tarsus)........... 7

— Hind tibia without prominent spines (smaller than third hind tarsus)........................... 8

7(6). Ensiform antennae, fastigium ‘horn-like’, prominent eyes and concave forehead.. Alophonota Stål, 1873

— Antennae not ensiform, fastigium prominent but not ‘horn-like’, less prominent eyes and straight forehead............................................................. Coryacris Rehn, 1909

8(6). Head proportionally much longer and globose in relation to the pronotum (lateral view); lack of a pronotum median carina.................................................................. 9

— Head proportionally shorter and less globose in relation to the pronotum (lateral view); median carina usually present....................................................................... 10

9(8). Transverse sulcus between vertex and fastigium conspicuous; pronotum median carina vestigial on metazona.............................. Costalimacris Carbonell and Campos-Seabra, 1988

— Limit between fastigium and vertex barely marked; pronotum median carina lacking on metazona............................................ Limacridium Carbonell and Campos-Seabra, 1988

10(8). Specimens brachypterous or without wings.................................................. 11

— Specimens macropterous................................................................. 12

11(10). Specimens without tegmina; dorsal and ventral margin of hind femur with small denticles............................................................................. Antandrus Stål, 1878

— Specimens brachypterous; dorsal and ventral margin of hind femur without small denticles.................................................................... Radacridium Carbonell, 1984

12(10). Body ornament with colorful thin lines and bands; black thin line throughout the hind femur and tibia......................................................... Gurneyacris Liebermann, 1958

— Body ornament with spots and bands; hind femur centerline in some species but absent in hind tibia or specimen without any brand in the legs................................................. 13

13(12). Fastigium and frons are usually angulated (lateral view); prozona almost the same size as the metazona; subgenital plate forked, terminalia less robust........................... Zoniopoda Stål, 1873

— Fastigium and frons are usually quite rounded (lateral view); prozona shorter than metazona; subgenital plate no forked, terminalia robust..................................... Diponthus Stål, 1861

14(5). Robust body and head; abdomen with conspicuous red punctuations in the dorsal, lateral, and ventral regions; hind tibiae usually red, hind femur and tibiae without bands............................................................................ Xestotrachelus Bruner, 1913 ( Fig.1– 2 )

— Body and head not so robust; abdomen without red punctuations; hind tibiae not red, hind femur and tibiae usually with colorful bands.................................. Chromacris Walker, 1870

Figures

Figure 1. Live Xestotrachelus robustus (Bruner, 1911) specimens collected at Panga Ecological Reserve. A) Males trying to copulate with the female (bigger one). B) Female dorsal view. C) Female abdomen with red punctuations in the dorsal, lateral, and ventral regions.

Figure 2. Pinned specimens of Xestotrachelus robustus (Bruner, 1911) collected at Panga Ecological Reserve. A) Female. B) Male. Scale bar = 0.5 cm.