Research Article |
Corresponding author: Klaus-Gerhard Heller ( heller.volleth@t-online.de ) Academic editor: Ming Kai Tan
© 2021 Klaus-Gerhard Heller, Matthias Helb.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Heller K-G, Helb M (2021) Revision of the tusked bush-crickets (Tettigonioidea: Pseudophyllinae: Dicranostomus) with description of the hitherto unknown sexes. Journal of Orthoptera Research 30(1): 87-94. https://doi.org/10.3897/jor.30.62170
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The genus Dicranostomus belongs to the very few Orthoptera with elongated mandibular processes, here called tusks. However, it is also one of the least studied genera from whose two species only one female and two males have been known so far. We present additional material from both species and sexes that confirms that the males have the relatively longest (2–2.8 times pronotal length) tusks of all Orthoptera. Surprisingly, the females of both species differ in this character: females of D. monoceros have tusks and those of D. nitidus do not. Based on a comparison with other species, we hypothesize that the species use holes that males can defend and use to monopolize the females.
Eucocconotini, mandible, Peru, South America, taxonomy, weapon
In many species of animals, males possess elaborate structures used mainly in intraspecific fights over access to females (
Such weapons are relatively rare among Orthoptera. There are some species where the mandibles are enlarged only in males (see review in
All specimens were dried, pinned, and photographed using a CANON EOS 1200D. Photos of cerci and mirrors were taken using a dissecting microscope (OLYMPUS SZ Binocular Stereo Zoom Microscope) and a digital camera (SONY Cyber-shot DSC-P120). The inter-tooth distances were measured as the mean between every eleven teeth (ten intervals), starting at the anal end, using ADOBE PHOTOSHOP Elements 6.
The specimens, collected between 2013 and 2018, were obtained from a trader with an export license (http://gerfor.regionloreto.gob.pe/dublincore/biblioteca/descargar/4269/4500000100020_7.PDF).
Depositories.—
CH Private collection of K.-G. Heller;
C_Helb Private collection of M. Helb;
ISNB Institut Royal des Sciences Naturelles de Belgique, Brussels, Belgium;
MZPW Polish Academy of Science, Museum of the Institute of Zoology Warszawa, Poland.
Taxonomy
Family Tettigoniidae Krauss, 1902
Subfamily Pseudophyllinae Burmeister, 1838
Tribe Eucocconotini Beier, 1960
Dicranostomus monoceros Dohrn, type species by original monotypy
[based on
Medium sized (body length 2.5–4.0 cm), yellowish-brown animals (habitus; Fig.
South America, Peru (Fig.
1 | Pronotum weakly granulated. Knees and spines on legs black | D. monoceros |
– | Pronotum smooth, glossy. Spines on legs and knees same color as leg | D. nitidus |
Dicranostomus monoceros Dohrn, 1888: 362
PERU • ♀; Cumbasi Peruviae ad Huallagam; [Cumbaza]; MZPW. [photos in
PERU • 2♂; San Martin Region, Prov. Rioja, Nueva Cajamarca; 10 Nov. 2016; local collector; C_Helb8771-C_Helb8772 • 1♀, 1♂; San Martin Region, Prov. Rioja, Nueva Cajamarca; Mar. 2018; local collector; C_Helb8773-C_Helb8774 • 2♂; San Martin Region, Prov. Rioja, confluente Altomayo river/Naranjos; 8 Mar. 2018 & 25 Apr. 2018; local collector; C_Helb8775, ♂ C_Helb8776.
Up to now, the species was known only by the female holotype. In one female (C_Helb8773), the right foreleg is irregularly developed. Its tibia does not have a tympanic organ or dorsal black tubercles (Fig.
General characters as genus.
Male. Fastigium frontis elongated horizontally (Fig.
Female. General characters as genus and male. Mandibles each with one long (0.8–0.9 times as long as pronotum), slightly upcurved process (tusk). Subgenital plate transverse, at the end straightly cut and distally slightly notched in the middle.
Coloration. Head with tusks and pronotum chestnut (tusks becoming darker towards the tips); legs yellowish, but knees, tympanic organ and tubercles in the fore tibia and larger spines in all legs black. Tegmina as in D. nitidus (see below). In some animals, the anterior and central lower parts of the paranota are brighter and more yellowish than the other parts.
See Table
Dicranostomus nitidus Brunner von Wattenwyl, 1895: 180
PERU • no details; ISNB. [photos in
PERU • 1♂; Department of Huanuco, Fundo Sinchono, 37 miles east of Tingo Maria on the road to Pucallpa; 1700 m a.s.l.; 5 Aug. 1947; Jose Schunke leg.; (
PERU • 1♂; Oxapampa; Feb.–Apr. 1984; Rainer Marx leg.; CH4220 • 1♂, 1♀; Prov. Huanuco, Huanuco Road, between Huanaco and Tingo Maria, Malqui [Macora?] town, fog area [sic]; Aug. 2013; local collector; C_Helb8769-C_Helb8770 • 1♂; San Martin Region, Prov. Rioja, Nueva Cajamarca; Mar. 2018; local collector [assumed exchange of labels—see list for localities of monoceros]; C_Helb8777
The species was known only by the male holotype and another male, described by
General characters as genus.
Male. Fastigium frontis elongated horizontally (Fig.
Female. General characters as genus and male. Fastigium frontis elongated vertically (Fig.
Coloration. “Head, thorax and legs chestnut, the tibiae darker, the mandibular appendages practically black, palpi pale. …. tegmen with veins brown, cellules and membrane yellowish, much brighter toward base in costal area; wing with veins pale brown, membrane slightly fuscous“ (
See Table
Measurements of males and females of both species of Dicranostomus (*data from
Species | Specimen | Sex | Measurements (in mm) | ||||||||
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# | body | body + tusk | pronotum | fore femur | hind femur | tegmen | antenna | tusk | ovipositor | ||
D. monoceros | type* | ♀ | 28 | 6.5 | 10.5 | 19 | 27 | - | 6 | 15 | |
C_Helb8773 | ♀ | 32 | 35 | 6.5 | 10.5 | 16.5 | 23 | 120 | 5.5 | 15.5 | |
C_Helb8771 | ♂ | 27 | 41 | 6 | 10 | 14.5 | 20 | 95 | 16 | ||
C_Helb8772 | ♂ | 32 | 44 | 7 | 11 | 16 | 21.5 | 95 | 15 | ||
C_Helb8774 | ♂ | 29 | 44 | 6 | 10.5 | 15.5 | 22 | 95 | 16.5 | ||
C_Helb8775 | ♂ | 27 | 40 | 6.5 | 10.5 | 16 | 21 | - | 16.5 | ||
C_Helb8776 | ♂ | 28.5 | 40 | 6.5 | 15.5 | 21 | 80 | 17 | |||
D. nitidus | type* | ♂ | 30 | 7 | 11.5 | 20 | 22 | - | 14 | ||
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♂ | 35 | 58 | 7.5 | 12 | 19 | 26 | - | 20 | ||
CH4220 | ♂ | 38 | 53 | 7.5 | 12 | 20.5 | 27 | - | 18 | ||
C_Helb8769 | ♂ | 36 | 47 | 7.5 | 12 | 19.5 | 26 | 72 | 13.5 | ||
C_Helb8770 | ♀ | 33 | - | 7.5 | 12 | 20 | 28.5 | 100 | 17.5 | ||
C_Helb8777 | ♂ | 36 | 49 | 7.5 | 13 | 19 | 27.5 | 68 | 17 |
The genus Dicranostomus belongs to the tribe Eucocconotini, which is part of the supertribe Pleminiiti Brunner von Wattenwyl, 1895 (
Dicranostomus
and Gnathoclita are also similar in the shape of their mirrors (compare Fig.
Unfortunately, no data are available concerning the function of the most distinctive structure of Dicranostomus: the tusks. These tusks are the longest found among Orthoptera in comparison to the male body size (measured relative to pronotal length) and are clearly longer than in the well-known tusked wetas (Table
Species | Specimen(s) | Sex | Length (in mm) of | Tusk length /pronotum length | Source | ||
---|---|---|---|---|---|---|---|
pronotum | hind femur | Tusk (range) | |||||
D. monoceros | mean | ♂ | 6.4 | 15.5 | 16.2 (15.17) | 2.5 | this paper |
mean | ♀ | 6.5 | 17.8 | 5.8 (5–6) | 0.9 | this paper | |
D. nitidus | mean | ♂ | 7.4 | 19.6 | 17.1 (18–27) | 2.2 | this paper |
Motuweta isolata | holotype | ♂ | 15 | 38.0 | 26.0 | 1.7 | Johns 1997 |
paratype | ♂ | 10 | 28.0 | 9.0 | 0.9 | Johns 1997 | |
mean | ♂ | 12.5 | 33.0 | 17.5 | 1.4 | Johns 1997 | |
Motuweta riparia | mean | ♂ | 7.7 | 24.0 | 6.4 (3–12) | 0.8 |
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Anisoura nicobarica | holotype | ♀ | 4.6 | 10.6 | 0.0 |
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syn. monstrosa | ♂ | 6.0 | c. 1.3 |
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Libanasidus vittatus | mean | ♂ | 9 | 21.5 | 7.5 (7–8) | 0.8 |
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Libanasa capicola | holotype | ♂ | 17.0 | 7.0 | 0.8 | from figure; |
We are grateful to Holger Braun, Sigfrid Ingrisch, Ming Kai Tan, and an anonymous referee for helpful comments on the manuscript. The Orthopterists’ Society provided free publication of this paper. Duplication of information presented in