Myrmecophilus acervorum
Creators: name: Iorgu, Ionuț Ştefan
name: Iorgu, Elena Iulia
name: Stalling, Thomas
name: Puskás, Gellért
name: Chobanov, Dragan
name: Szövényi, Gergely
name: Moscaliuc, Liviu Aurel
name: Motoc, Rozalia
name: Tăuşan, Ioan
name: Fusu, Lucian
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Orthoptera
Myrmecophilidae
Myrmecophilus
Myrmecophilus acervorum

description: DESCRIPTION OF MYRMECOPHILUS ACERVORUM
Measurements
Adult male (N = 20): body length 2.5–2.7 mm; pronotum 0.6–0.7 mm long and 1.2–1.3 mm wide; hind femur 1.2–1.3 mm; hind tibia 1–1.1 mm; hind basitarsus 0.6– 0.7 mm; cerci 0.9–1 mm; subgenital plate 0.3 mm long and 0.5 mm wide.
Adult female (N = 22): body length 2.5–2.8 mm; pronotum 0.6–0.7 mm long and 1.2–1.3 mm wide; hind femur 1.2–1.3 mm; hind tibia 1–1.1 mm; hind basitarsus 0.6–0.7 mm; cerci 0.8–0.9 mm; subgenital plate 0.2 mm long and 0.3 mm wide; ovipositor 1.4–1.5 mm.
Length of hairs (both sexes): 30–40 µm on frons; 45–50 µm on antennae; 35–60 µm on pronotum and abdomen.
Description of male (Figs 1A, 2A, B, C, D, E, 3A, B)
Body slightly flattened dorsoventrally, weakly convex, 2.1–2.2 × as long as wide. Pronotum domeshaped, narrowed distally. Body and legs densely covered with a single type of hairs. The hairs are relatively short, shiny, and pointed, each with 26–35 costae.
Body colour reddish brown to dark reddish brown. Posterior margins of pronotum and mesonotum with a contrasting pale ochreous transversal band, and similar but less pronounced and narrower pale bands present on posterior margins of metanotum and tergites 1–3. Antenna about 1.1 × as long as body, dark ochreous, with massively inflated scape. Scape, pedicel, and apex of flagellum pale ochreous. Eyes dark grey or black. Palpi ochreous. Hind femur 1.5 × as long as wide; hind tibia with four subapical spurs on inner side. First segment of hind basitarsus with one dorsal spine in proximal third and two apical spurs. Epiproct small, with a slight, angular emargination, about 1.2–1.3 × as long as wide. Cercus round in transversal section, pointed apically, densely covered with hairs and sensilla. Phallic complex consists of a U-shaped epiphallus and a translucid ectophallus, with a pair of spiny, band-shaped apical sclerites. Subgenital plate distinctly emarginated.
Description of female (Figs 1B, 2F, 3C)
The appearance of the female, apart from the genital structures, largely corresponds to that of the male and it was comprehensively described and illustrated by Junker (1997), Schimmer (1909) and Stalling & Birrer (2013).
COMPARATIVE DIAGNOSIS
Within the continental Balkans, M. acerƲorum can be distinguished from the other five co-occurring species, firstly, by the body colour. The characters discussed below hold both for the female and for the newly discovered male. For a more detailed analysis, the type of hairs, shape of female ovipositor and subgenital plate, and the hind basitarsus spines should be considered.
In M. acerƲorum, the body colour is reddish brown to dark reddish brown with contrasting, pale ochreous broad bands on the posterior third of the pronotum and posterior third of the mesonotum, and less pronounced and narrower pale bands on the posterior margins of metanotum and the first three abdominal tergites. Regarding coloration, Myrmecophilus balcanicus is pale brown with the following contrasting pale ochreous: posterior half of the pronotum, mesonotum completely, and the posterior margins of metanotum and the subsequent tergites. The coloration of Myrmecophilus nonƲeilleri is rusty brown with narrow, pale posterior borders on the pronotum or abdominal tergites; the coloration is uniformly dark brown in Myrmecophilus hirticaudus Fischer von Waldheim, 1846 and pale ochreous in Myrmecophilus myrmecophilus (Savi, 1819) with no (M. hirticaudus) or only inconspicuous (M. myrmecophilus) pale ochreous posterior border on the pronotum or abdominal tergites; Myrmecophilus ochraceus Fischer, 1853 is dark ochreous with rufousochreous pronotum, which is only slightly paler posteriorly. Beside the body colour, M. acerƲorum can be distinguished from the other Myrmecophilus species by its pilosity. In M. acerƲorum, the pronotum and tergites are densely covered with only one type of inclined, relatively short, shiny hairs. The arrangement of the hairs appears regular and the distance between them is almost as large as their length (Stalling & Birrer, 2013). Myrmecophilus balcanicus has the pronotum and the tergites densely covered with much shorter, inclined, sparse hairs (Stalling, 2013c). Myrmecophilus myrmecophilus has the pronotum and the tergites densely covered with inclined, sparse, relatively long hairs, scrubby aligned. Two types of hairs cover the body of M. hirticaudus: few prominent hairs and many short, close-fitting hairs. In M. ochraceus, the pronotum and tergites are densely covered with short, inclined, hairs, and the hairs on the frons and antennae are unlike those in all other species, being long, sparse and bushy. The shape of female subgenital plate can also be used when separating some ant cricket species. The females of M. myrmecophilus and M. ochraceus have a rounded or distally slightly emarginated subgenital plate, whereas M. acerƲorum, M. balcanicus and M. hirticaudus have distinctly emarginated subgenital plates. In M.nonƲeilleri the apex is slightly emarginated or truncate (Stalling, 2013c; Stalling & Birrer, 2013).
Previously considered as the main identification traits for Myrmecophilus (Bacetti, 1966; Harz, 1969), the number and position of the spines on the hind basitarsus seem to be highly variable in several species. For example, in the Central European and North Mediterranean species of the genus, only M. hirticaudus has three dorsal spines, positioned on the proximal, medial and distal parts of the hind basitarsus. Two or three spines variably occur in M. myrmecophilus, the distal one being usually absent, while in M. acerƲorum and M. aequispina the distal spines are always absent (Stalling & Birrer, 2013). The continental Balkan species can be grouped as follows: basitarsus of the hindleg with a single spine in the proximal third (M. ochraceus), hind basitarsus with two dorsal spines in proximal and median positions (M. acerƲorum, M. balcanicus, M. myrmecophilus), hind basitarsus with two or three spines (M. nonƲeilleri) and hind basitarsus with a constant number of three dorsal spines, positioned in the proximal, median and distal parts (M. hirticaudus) (Stalling & Birrer, 2013).
SEQUENCE CHARACTERISTICS
We obtained a total of 93 sequences (52 for COI and 41 for 16S), from 42 individuals of M. acerƲorum and from 11 other Myrmecophilus individuals used as outgroup and in species delineation analyses (Supporting Information, Table S1). We obtained a final concatenated alignment of 1183 bp with 937 constant sites and 239 variable sites out of which 185 are parsimony informative (Table 1). We identified a total of 19 haplotypes, ten for the ingroup and nine for the outgroup (Supporting Information, Table S1). In the ingroup, we identified 18 polymorphic sites out of which only three were parsimony informative. Nucleotide model of evolution for the concatenated set of data was determined as GTR with gamma distributed rate differences among sites (Table 1). Genetic differentiation between nominal species of Myrmecophilus varied between 2.66 % and 18.53% (Table 2), while the mean intraspecific distance varied from 0.24% to 0.91%.
description: Published as part of Iorgu, Ionuț Ştefan, Iorgu, Elena Iulia, Stalling, Thomas, Puskás, Gellért, Chobanov, Dragan, Szövényi, Gergely, Moscaliuc, Liviu Aurel, Motoc, Rozalia, Tăuşan, Ioan & Fusu, Lucian, 2023, Ant crickets and their secrets: Myrmecophilus acerŋorum is not always parthenogenetic (Insecta: Orthoptera: Myrmecophilidae), pp. 211-228 in Zoological Journal of the Linnean Society 197 (1) on pages 216-219, DOI: 10.1093/zoolinnean/zlab084, http://zenodo.org/record/7471675