Cholovocera Victor, 1838

Delgado, Juan A. & Palma, Ricardo L., 2023, A revision of the genus Cholovocera Victor, 1838 (Coleoptera: Endomychidae), European Journal of Taxonomy 906, pp. 1-71 : 5-18

Genus Cholovocera Victor, 1838

Cholovocera Victor, 1838: 177 , pl. 3 fig. b.

Choluocera – Kraatz 1858: 140. Unnecessary replacement name.

Coluocera – Gemminger & Harold 1868: 905. Unjustified emendation.

Colovocera – Belon 1879: 185. Misspelling.

Type species

Cholovocera formicaria Victor, 1838 (by monotypy).

Remarks concerning authorship

Victor Ivanovich de Motschulsky (1810–1871) published papers under two names: “Victor, T.” and “Motschulsky, V. de” (also spelt “Motchoulsky”). However, various authors in many publications cited his name incorrectly, usually “Motschulsky” instead of “Victor”. In the case of Cholovocera , we agree with Sherborn (1926: 2483) and Jäch et al. (2016) in that “Victor” is the correct name of the author, and not “Motschulsky” as given in many publications.

Taxonomic history

The description of Cholovocera by Victor (1838) is accurate, except where he incorrectly described as bifid the last tarsomere of all legs. However, he correctly illustrated that tarsomere in his fig. b1. Conversely, although not mentioned in the text, his fig. b shows the length of all ventrites shorter than the metasternum, which is incorrect ( Fig. 1 ), and his fig. b3 shows ten antennomeres when, in fact, there are only eight ( Fig. 2C ). Erichson (1845: 125) included Cholovocera in the Coccinellidae, Redtenbacher (1858: 380 , 1874: 411) and Reitter (1875: 301) redescribed the genus, repeating the incorrect number of ten antennomeres, an error corrected to eight by Schaufuss (1876a: 394) and confirmed by Reitter (1877: 2). Des Gozis (1881: 142) translated Reitter’s (1875) paper into French, adding references and comments on morphology, correcting the number of antennomeres to eight, and including keys for the identification of genera and species. Both Ganglbauer (1899: 821) and Belon (1902: 5) redescribed Cholovocera again, reviewing the confusion about the number of antennomeres, and Belon (1902) added a list of known species and their distribution.

Rücker (1980: 142) published the first comprehensive revision of Cholovocera , comprising six species with their geographic distribution and a dichotomous key for their identification, including illustrations of male genitalia. Shockley et al. (2009b: 64), in their checklist of the world species of Endomychidae , listed the species of Cholovocera which they recognised as valid, including some junior synonyms (see below under Species included in Cholovocera ). Recently, Rücker (2018), in his revision of the western Palearctic Merophysiidae , published a key to the genera of that family, including Cholovocera , as well as descriptions, illustrations and a key to identify the species he placed in this genus. As will be shown below, our concept of a valid species of Cholovocera differs greatly from that of Rücker (2018: 568).

Species included in Cholovocera

Shockley et al. (2009b: 65) listed nine species in Cholovocera , including one which we consider to be a new junior synonym ( Ch. major ) and two which we do not regard as belonging to Cholovocera ( Coluocera beloni Wasmann, 1899 and “ Cholovocera ” brevicornis Johnson, 1977 ). Further, Shockley et al. (2009b: 65) regarded as junior synonyms two species which we consider valid: Ch. formiceticola ( Rosenhauer, 1856) and Ch. gallica (Schaufuss, 1876) . Considering the ten species included in Cholovocera by Rücker (2020: 34), we only agree with five of them. We do not recognise two species from the Neotropical Region ( Pseudevolocera atomarioides Champion, 1913 and Coluocera ecitonis Wasmann, 1890 ) and one from Afghanistan (“ Ch ”. brevicornis ) as belonging to Cholovocera , and we regard Co. formicaria major Reitter, 1887 and Co. punctata sardoa Reitter, 1911 as new junior synonyms. Furthermore, we consider as valid, three species which were listed by Rücker (2020: 34) as junior synonyms: Ch. balcanica ( Karaman, 1936), Ch. formiceticola and Ch. gallica . Finally, we found that Co. fleischeri Reitter, 1902 is a new junior synonym of Ch. gallica , and we describe one new species.

In conclusion, from our examination and study of 1878 specimens of Cholovocera , including types, we recognise eight valid species in Cholovocera : one new to science, three with new status and three junior synonyms, as follows:

Cholovocera formicaria Victor, 1838

Cholovocera subterranea Motchoulsky, 1845

Coluocera formicaria v. major Reitter, 1887 . Syn. nov.

Cholovocera punctata Märkel, 1845

Coluocera punctata sardoa Reitter, 1911 . Syn. nov.

Cholovocera formiceticola ( Rosenhauer, 1856) . New status

Cholovocera attae ( Kraatz, 1858)

Cholovocera gallica (Schaufuss, 1876) . New status

Coluocera fleischeri Reitter, 1902 . Syn. nov.

Cholovocera balcanica ( Karaman, 1936). New status

Cholovocera afghana Johnson, 1977

Cholovocera occulta Delgado & Palma sp. nov.

Generic descriptions

Adults, both sexes

Considering the morphological similarity among all the species of Cholovocera , this generic description includes diagnostic characters which will not be repeated in the species descriptions, but which will be mentioned only when they are diagnostic for species differentiation.

Total length, average 1.30 mm (range 1.20–1.60 mm). Body elliptical and dorsally convex, reddishbrown, with shiny smooth surface, finely punctured and slightly pubescent; setation decumbent and more evident ventrally ( Fig. 1 ).

HEAD. Rounded, slightly shorter basally and retracted into prothorax behind eye level ( Fig. 3A ). Eyes reduced to a single, prominent facet, protected by a lateral rim ( Figs 1A , 3A , 24E ). Antennae short, securiform, about 1/3 longer than head, eight-segmented: scape geniculate, antennomeres 1 and 2 long, 3 to 6 isodiametric, and terminal antennomere forming a subtriangular club, depressed dorsoventrally ( Fig. 2C ). Antennae inserted ventrally, and basally concealed by projections of frons, with the possibility of retracting in a ventral depression of the prothorax ( Fig. 1B : hp). Fronto-clypeal ridge strongly curved laterally; clypeus transverse, flat. Epipharynx with well-developed tormae ( Fig. 2B ). Labrum not visible from above, punctured, disc covered by sparse setae; anterior margin almost devoid of setae and lateral borders with a row of moderately long, recurved setae ( Fig. 2A ). Mandibles asymmetrical: right mandible with a semi-membranous, well-developed prostheca, several sclerotised teeth on its apical tip and some fringed sclerotised projections on the remainder of its external margin; penicillus well-developed ( Fig. 2F ). Left mandible with mola narrow, curved, without sclerotised teeth, with long, slender trichomes on its external margin, bearing a brush-like penicillus ( Fig. 2E ). Maxillae with a terminal palpomere as long as next two palpomeres combined, subcylindrical, rounded at apex and with many distal sensilla. Galea moderately broad, approximately three times as wide as the lacinia, with long broad apical spines and a developed subapical seta. Lacinia elongate, with some mesal spines ( Fig. 2D ). Labium with palpomere 1 slightly larger than palpomere 2, cylindrical, only moderately inflated; terminal palpomere subtriangular, with a row of sensilla at apex ( Fig. 2G ). Mentum transverse, with a middle large, triangular area finely punctured, disc covered with short and sparse setae ( Fig. 2G ). Prementum globose, membranous, with the sides of the ligula slightly lobulated ( Fig. 2G ). Hypopharynx lobulated distally ( Fig. 2H ). Tentorium ( Fig. 3A–B ) connected with base of head capsule by two inconspicuous posterior ventral pits ( Fig. 3A : vp); with anterior arms well developed ( Fig. 3A–B : aa); distal ends of anterior arms divergent, basal areas expanded and fused forming a laminatentorium ( Fig. 3A : la); dorsal arms short ( Figs 3A : da, 3B: da); posterior arms wide ( Figs 3A : pa, 3B: pa); corpotentorium absent.

THORAX. Pronotum transverse, widest at base ( Fig. 1A : pr); pronotal disc convex; surface coarsely and sparsely punctured; base of pronotum with a pair of small, dark, rounded shallow cavities; anterior margin sinuous with slightly produced, blunt angles; posterior angles obtuse, lateral margins sharply carinated ( Fig. 1A ). Prosternal process shaped as an hourglass ( Figs 1B , 4 ), well developed and separating the precoxae; in natural position, the prosternal process extends anteriorly concealing the base of the head ( Fig. 1B ). Hypomeron wide, with a pair of cavities, where the distal antennomeres can be retracted ( Fig. 1B : hp). Scutellum visible, subtriangular, with rounded vertices ( Fig. 1A : sc). Mesosternun with an anterior depression which accommodates the posterior border of the prosternal process ( Fig. 1B : ms). Elytra oval, convex, finely punctured ( Fig. 1A : el); epipleuron broad at base, narrowing towards apex, incomplete apically ( Fig. 1B : ep). Hind wings highly reduced, narrow basally, without any trace of venation and with a subquadrate distal portion ( Figs 1A : hw, 3C). Metasternum transverse ( Fig. 1B : mt); femoral lines distinct, complete ( Fig. 1B : fl). Legs compressed dorsoventrally: coxae circular in outline; trochanters broad and stout; femora sparsely setose; tibiae setose on the distal half, with an apical fringe of stout setae, and variable across species, from short, stout with straight sides to long, slender with sinuous sides; tarsi tri-segmented: tarsomeres elongate; claws simple; empodium (pretarsus) well developed, globose basally and pointed distally ( Fig. 1I ).

ABDOMEN. With five visible ventrites ( Fig. 1B ): ventrite 1 as long as ventrites 2 and 3 together; femoral lines obsolete; ventrites 2–4 equal in length; ventrite 5 slightly longer, with expanded lateral margins and rounded distal margin in females ( Fig. 5A ), but weakly depressed and slightly emarginated or truncated in males ( Fig. 6A ).

MALE TERMINALIA. The morphology of the terminalia is similar in all species: tergite 8 is formed by two plates, one external well sclerotised, covered by short setae, and one internal membranous ( Fig. 6C ). Sternite 8 is a much shorter transverse piece, well sclerotised and with a brush of long setae on its distal margin ( Fig. 6E ). Tergite 9 is formed by two hemitergites, without setae and closely associated with the proctiger (tergite 10 of some authors) ( Fig. 6B–F ). In addition, there is a Y-shaped spiculum gastrale ( Fig. 6D ).

AEDEAGUS. Formed of two fused pieces: a basal piece or phallobase ( Fig. 3D : bp) and a median lobe or penis ( Fig. 3D : ml), with only one dorsal paramere ( Fig. 3D : pm). The basal piece is spherical or oval in ventral view, in some specimens slightly elongated in lateral view; it is lightly sclerotised with very thin walls, and with a very wide lumen where an entwined ejaculatory duct can be seen through transparent walls ( Fig. 3D : ed). The duct emerges through a basal foramen ( Fig. 3D : fo), circular or oval surrounded by a sclerotised ring, on the ventro-distal side of the basal piece ( Fig. 3D : sr); the foramen is a useful reference to observe the aedeagus in an uniform standard position allowing comparisons among species and avoiding differences due to orientation.

The median lobe is an asymmetrical piece in ventral view, well sclerotised, dorso-laterally flattened and of variable size among species: relatively short with a wide base in some species, or much longer than wide and medially sinuous in others; in both cases it tapers towards its apex and bends to the right side in ventral view ( Fig. 3D : ml). The morphology of the median lobe is constant within species and of good taxonomic value.

The paramere is formed of two parts: one basal, laminar, lightly sclerotised, partially surrounding the median and basal sections of the median lobe, and another part distal, conical and slightly elongated; the distal section is much more sclerotised with two areas separated by a narrow, dorsal, clear band, each area carrying several setae; the basal part has two short setae, but the distal part has a variable number of setae, between two to eight ( Fig. 3D : pm). Only Ch. formiceticola , lacks these distal setae.

The morphology of the distal section of the aedeagus is constant within species and can be used as a useful diagnostic character among species.

Female terminalia. The ovipositor is formed by a pair of gonocoxites ( Fig. 5B : va, st) articulated with the paraprocts or laterotergites ( Fig. 5C : pp); the gonocoxites are dorsally covered by the proctiger (tergite 10 of some authors) ( Figs 5B : pg, 5E) just above the anus, and are formed by two sections: one proximal, the valvifer ( Fig. 5B : va) and one distal, the stylus ( Fig. 5B : st); the valvifer carries several distal setae, and shows slight variation across species, mainly in its width, but we do not consider it of taxonomic value; the stylus has a pair of long distal setae, but it does not vary morphologically among species. Both valvifer and stylus are dorsally covered by tergite 8 ( Fig. 5C ), which has a rounded margin and a row of marginal short setae, and ventrally covered by sternite 8 ( Fig. 5D ). Our detailed study of the female ovipositor has shown that it is not a diagnostic character to differentiate species.

The spermatheca is a relatively simple organ in most species of Coleoptera , formed by three main parts: the reservoir, the duct and the accessory gland. De Marzo (2008) described five main types of spermathecae in beetles, depending on the absence or relative development of one of those parts. In Cholovocera , the spermatheca ( Fig. 7 ) has the main three parts and is similar to those of species of the family Coccinellidae ( De Marzo 2008) . The spermathecal duct is a simple, short tube ( Fig. 7D : sd), which connects the spermathecal reservoir with the bursa copulatrix; the spermathecal reservoir is T-shaped with thin, soft walls, formed by a distal area called the cornu ( Fig. 7D : co), slightly more sclerotised with variable morphology in different species, and a proximal area called the ramus ( Fig. 7D : ra), usually sacciform, with wrinkled walls allowing considerable dilation; the basal branch of the reservoir is the nodulus ( Fig. 7D : no), which connects to the spermathecal duct. This is the region of the spermatheca with most morphological variability among the species of Cholovocera ( Fig. 7 ). The nodulus has two parts which vary in shape, thickness and length: one distal, narrower, joining with the spermathecal duct; another proximal, wider, attached to the ramus. Between the nodulus and the ramus is the spermathecal gland ( Fig. 7D : sg), a long, narrow sac of uniform morphology among all the species.

Preimaginal stages

Lawrence (1991) and Tomaszewska (2000, 2010) contributed data on larvae of Endomychidae in general, but the only information on preimaginal stages of species of Cholovocera was published by Silvestri (1912), who described the egg, larva and pupa in detail. Silvestri (1912) described the egg as white, sub-elliptical, 0.546 mm long and 0.351 mm wide, with a smooth surface, but slightly reticulated when observed at high magnification. The larva is elongated, slightly depressed dorsoventrally and tapering towards both ends, measuring approximately 2.3 mm long in the last instar. The head, darker than the body, has convex sides without stemmata (synapomorphy for the subfamily), and very short antennae. The mandibles are subtriangular short, robust, with curved anterior facies, a tricuspid apex and a developed mola, without prostheca. The maxillae and labia are short and robust. The thorax wider than the head, with short, thick legs. Silvestri (1912) also included a figure showing the dorsal and ventral views of the larva, with details of the cephalic capsule, its appendices, plus the legs. Furthermore, Silvestri (1912) briefly described the chaetotaxy of some body parts, in particular the dorsal abdominal setae, clearly capitate, and the ventral abdominal setae not capitate. In addition, Silvestri (1912) described the pupa as whitish, 1.35 mm long, with a figure showing it in dorsal and ventral views.

Biology

Feeding habits

Tomaszewska (2010) suggested that fungi is the principal food of the family Endomychidae . Skelley & Leschen (2002) mentioned spores and hyphae of microfungi as the food of species of Merophysiinae . However, Shockley et al. (2009b) expressed doubt about what food endomychid species feed on inside ant nests, suggesting that some tropical species may feed on the fungal gardens cultivated by the ants or just feed on adventive fungi growing inside the ant nest. Rücker (2018) adds to these theories, mentioning that the adult mouth parts of these beetles are compatible with mycophagy, and even with eating ant larvae.

Following on the work by Silvestri (1912), Baroni-Urbani (1963) made an important contribution to the knowledge of the biology of Cholovocera , studying what he identified as Ch. formicaria from Ancona ( Italy), but likely to have been Ch. gallica , the most frequently found species on mainland Italy (see below). Baroni-Urbani (1963) collected 148 beetles from one medium size colony of Messor capitatus (Latreille, 1798) and observed that they occupied food stores and cells where waste material accumulates, eating remains of seeds previously eaten by ants.Also, Baroni-Urbani (1963) observed that, occasionally, the beetles would feed on insect remains left by the ants, which they eat as complement to their granivorous diet; however, he did not observe any beetle consuming anything alive, neither ant eggs nor ant larvae, as they only fed on dead insects killed by the ants.

Our analysis of some beetle gut contents has shown a high proportion of unidentifiable vegetal remains ( Fig. 8B ), but also spores and hyphae ( Fig. 8C–E ) and some remains of arthropod cuticle ( Fig. 8F ). In conclusion, available data would indicate that the species of Cholovocera have followed the same pattern of other groups of myrmecophilous Coleoptera , initially fungivorous but adapted to a more varied diet, eclectic and opportunist, as discussed by Schigel (2012).

Behaviour and myrmecophily

In his original description of the genus, Victor (1838) wrote that Ch. formicaria was a slow-moving species, but Lucas (1849) qualified as very agile a species (probably Ch. punctata ) that he observed in Algeria. Again, Lucas (1874) regarded a species from southern France as agile. From our observations of Ch. formiceticola on external foraging tracks of Messor barbarus (Linnaeus, 1767) , the beetles initially move slowly, but then increase their pace at irregular intervals. In contrast, our observations of Ch. formiceticola inside ant nests in the laboratory show that these beetles move slowly most of the time, as recorded by Victor (1838). However, if they are suddenly exposed to light, they seek refuge rapidly, this being a possible explanation of the observations by Lucas (1849, 1874).

Myrmecophily has been variously described, but Kistner’s (1982) definition is one of several widely accepted. Myrmecophily can be present in four symbiotic types, according to the benefit received by the ants, in decreasing order: mutualism, commensalism, kleptoparasitism and parasitism. Species of Cholovocera are placed between commensalism and kleptoparasitism. Victor (1838) was the first to record the association between Cholovocera and ants, clearly shown by the name he chose for his new species: Ch. formicaria . Märkel (1845), while describing Ch. punctata , suspected its association with ants but he could not confirm it. Lucas (1849) and other early authors mentioned that the beetles were associated with ant nests or that they were collected under stones together with ants. Belon (1879) again drew attention to the myrmecophilous character of species of Cholovocera , assuming that these beetles lived in a “peaceful” relation with ants, and citing a case where he found specimens in abandoned ant nests. This observation indicates that Cholovocera beetles may survive in the nest without the presence of ants.

Krausse (1911) reported an experiment in which he placed a group of ants ( Messor barbarus ) in a small breeding container together with several myrmecophilous arthropods collected in Sardinia, i.e., beetles (including some Ch. punctata ), termites, silverfish and isopods. On the following day, he observed that the ants had eaten all the silverfish, but not the remaining specimens. A further observation was that one specimen of Ch. punctata was on top of an isopod, which made Krausse (1911) suggest that these beetles may use other commensals to move inside the ant nest. In our opinion, that behaviour may have been an artefact resulting from the artificial nature of the environment where the experiment was performed.

Silvestri (1912) provided useful behavioural data based on his observation of hundreds of Cholovocera beetles, which he identified as “ Ch. formicaria ”, from various localities in southern Italy, all associated with nests of species of Messor Forel, 1890 . Judging from the localities cited by Silvestri (1912), we deduce that the species would have been Ch. punctata and/or Ch. gallica . Silvestri (1912) placed several adult beetles inside artificial ant nests, observing their behaviour for several months, from November 1910 to September 1911. He wrote that the beetles acclimatised very well to these conditions and that during the summer of 1911 there were eggs and larvae. Further, he commented that Cholovocera adults mostly lived inside chambers where the ants kept grains, but that they laid eggs in chambers with debris and/or grain infested by fungi, where eggs would hatch, larvae develop and pupate. Also, Silvestri (1912) commented that any interaction between beetles and ants was low. These observations largely agree with ours, also made from nests in the laboratory ( Fig. 8A ). According to Silvestri (1912), if a worker ant attempted to capture a beetle with its mandibles, the victim would manage to free itself, due to its robustness, smooth surface and elliptical shape; however, Cholovocera larvae were totally ignored by the ants.

Escherich (1917), possibly based on Silvestri’s (1912) observations, qualified the genus Cholovocera as myrmecophilous in a synoecy, a strategy where ants are indifferent to their cohabiting beetles. Baroni-Urbani (1963) observed that the beetles avoided the ants as much as possible, moving carefully within the galleries from one food chamber to another and seeking refuge within wall cracks, while they were not feeding. Baroni-Urbani (1963) also described a digging behaviour by the beetles, which used their heads and thorax as a shovel to dig and hide inside the substrate. According to Baroni-Urbani (1963), the ants appear to accept these beetles without attacking them, possibly because they are saprophagous inquilines which, in some way, assist by eliminating unwanted waste.

Our field observations agree with the above ones, i.e., Cholovocera beetles move over foraging tracks and around the entrance to the nest being completely ignored by the ants. However, we observed that some beetles introduced into ant nests held in the laboratory, are eaten by the ants few hours after being inside the nest, only sometimes surviving a few days. This scenario would indicate the beetles may have to first acquire the pheromone odour of the ant nest to survive inside it.

Some authors recorded the identity of ant hosts when publishing about Cholovocera . Wasmann (1894), Bernard (1968) and more recently Shockley et al. (2009b) included tables with limited data on Cholovocera myrmecophily, but without new records or comments. In general, published data indicate that species of Cholovocera are mainly associated with ant species of the subfamily Myrmicinae , especially of the genus Messor and, to a lesser extent, with those of Aphaenogaster Mayr, 1853 , Pheidole Westwood, 1839 and Tetramorium Mayr, 1855 ( Karaman 1964). Also, there are few records of associations with species of Camponotus Mayr, 1861 (Formicinae) ( Donisthorpe 1927; Karaman 1964). From our study of museum collections and from our own collecting, we agree that ant species of the five genera mentioned above are the hosts of Cholovocera beetles, in the same order of abundance. Cholovocera attae, Ch. formiceticola and Ch. occulta sp. nov. are exclusively associated with species of Messor , as well as most of the specimens of Ch. balcanica, Ch. gallica and Ch. punctata . However, we found Ch. formicaria associated with only one species of Tetramorium , and the host of the sole specimen we examined of Ch. afghana was Pheidole indica Mayr, 1879 .

Because of the dubious identifications of Cholovocera species in the literature, even in recent publications, we feel that giving a complete list or table of published ant host-beetle associations will be confusing rather than useful. However, under the treatment of each Cholovocera species, we discuss published erroneous ant host-beetle associations and establish what we believe are true associations.

Parasites, commensals and phoresy

Shockley et al. (2009a: 6) wrote that pathogens, such as bacteria of the genus Wolbachia Hertig, 1936 , had not been recorded from any member of the family Endomychidae , but they mentioned records of an ectoparasitic fungus of the genus Rickia Cavara,1899 (order Laboulbeniales ) infesting several species of Endomychidae in some Asian and African localities. However, no species of the subfamily Merophysiinae is mentioned as host of any parasite. Shockley et al. (2009a) failed to cite a paper by Santamaría (1995) where the species Parvomyces merophysiae (order Laboulbeniales ) was newly described, parasitising specimens of the beetle Merophysia formicaria Lucas, 1852 , from material collected at Lérida, in the northeast of the Iberian Peninsula.

During our examination of many specimens of Cholovocera , we found a few beetles of the species Ch. formiceticola from Lisbon ( Portugal) with thalli of a fungus on their legs ( Fig. 8G–H ). The perithecium ( Fig. 8H : pe) of these fungi was attached to the insect cuticle by a basal area or stalk ( Fig. 8H : sk) and these structures are diagnostic for their identification. Although our specimens resemble Parvomyces merophysiae , a more detailed study is needed to confirm their identity, as they may represent an undescribed species (S. Santamaría pers. comm. February 2022).

Shockley et al. (2009a: 6) do not mention any endoparasite known to infest any endomychid species, they only list several yeast species as endosymbionts of eight endomychids but, again, no Merophysiinae is mentioned ( Shockley et al. 2009a: Table 2). However, we found cysts of a protozoan in the Malpighian tubes ( Fig. 8I ) of four species of Cholovocera : Ch. formiceticola from southeastern Spain, Ch. punctata and Ch. gallica from Sicily, and Ch. formicaria from Azerbaijan. All the cysts studied were morphologically similar: elliptical with rounded poles and refractive, measuring 9.5 µm long by 6 µm wide, and occupying almost the entire lumen of the Malpighian tubes ( Fig. 8J ). These cysts do not appear to affect other organs of the beetles, and we could not find them in other species present in the same ant nest, i.e., ants ( Messor barbarus ), springtails ( Collembola) and silverfish (Zygentoma).

In an attempt to further identify this protozoan, we placed the internal organs of one beetle in a saline solution for approximately 15 hours, after which we observed that the cysts opened, producing an amoeboid phase, mobile but without pseudopods. These features suggest that it belongs to the Amoebozoa, a large group of protists, including some pathogenic species (C. Lange, pers. comm. May 2022). Lange & Lord (2012) reported that a few species of Amoebozoa invading the Malpighian tubes of insects are, placed in three genera: Malpighiella Minchin, 1910 , Malpighamoeba Prell, 1926 and Malamoeba Taylor & King, 1937 ; however, we were unable to further identify our specimens. Lange & Lord (2012) wrote that the immature phase of these protozoans moves from the insect gut or the body cavity into the Malpighian tubes, completely occupying the lumen of the tubes as cysts. This feature agrees with our observations in species of Cholovocera .

Considering the large number of Cholovocera beetles that we examined for this revision, and the small number that we found with parasites or commensals, we agree with Shockley et al. (2009a) in that these symbionts are rare in species of Endomychidae .

Shockley et al. (2009a: 6) stated that phoresy on species of Endomychidae is rare compared to other beetle families of similar habits, and that the most frequent phoretics of endomychids are mites, mostly of the subfamily Rhizoglyphinae and, to a lesser extent, of the Uropodinae. On a specimen of Ch. gallica from Sicily, we found three deutonymphs of a mite belonging to the Rhizoglyphinae ( Fig. 8K–L ). According to Dr P. Klimov (pers. comm. 7 Feb. 2022), our mites may belong to one of three genera: Sancasania Oudemans, 1916, Schwiebea Oudemans, 1916 , or Rhizoglyphus Clapadère, 1869 , but a detailed examination is needed to achieve an identification.

Geographic distribution

The distribution of most species of Cholovocera is on the south-west of the Palearctic Region ( Fig. 9 ), with a few populations north of the Black Sea, one species on the Caucasus Mountains and the Caspian Sea coast, and another species reaching Afghanistan ( Fig. 9C ). Seven species are distributed around the Mediterranean Sea ( Fig. 9 ), agreeing with the chorologic distribution Turanic-Mediterranean, as proposed by Vigna-Taglianti et al. (1992). There are published citations of Cholovocera outside these areas but, as it will be discussed below, they refer to species which we do not regard as belonging to this genus.

Furthermore, due to a number of published misidentifications of species of Cholovocera , as mentioned in the Introduction above, current distributional data for the species of this genus are questionable. Even the more recent distributions given by L̂bl & Smetana (2007), Shockley et al. (2009b), and Rücker (2020) must be critically revised. Therefore, under each species treatment below, we give a list of the specimens examined, include what we consider the correct distributional data, and discuss which specimens we regard as misidentifications and/or erroneous locality records.

According to the locality data associated with our material examined, we conclude that, where two or more Cholovocera species are sympatric (in north-eastern Spain, southern France, western Italy, Sardinia, Sicilia, northern Africa, Greece and Turkey), they are rarely found at exactly the same locality, and two species are seldom found in the same ant nest. We are aware of only two cases where two or more species of Cholovocera were recorded in the same ant nest: one is a report by Stalling (2019), who found several beetles of the species Ch. attae and Ch. balcanica (as Ch. major ) inside an abandoned ant nest; the other is from our own examination of one female of Ch. gallica sharing the same ant nest with several specimens of Ch. punctata in Sicily. However, more often, species of Cholovocera may share an ant nest with other myrmecophilous beetles. Species of Cholovocera are frequently found with the tenebrionid Oochrotus unicolor Lucas, 1852 ( Bargagli 1872; Parmentier et al. 2020), or with species of Merophysiidae . For example, Ch. afghana has been collected together with Displotera beloni ( Wasmann, 1899) in Afghanistan (as “ Ch. brevicornis Johnson, 1977 ”, see below). In Spain, we found Ch. formiceticola sharing ant nests with species of Merophysia Lucas, 1852 and we have examined specimens of Ch. attae and Reitteria escherichi Wasmann, 1896 collected from the same ant nest in western Anatolia (see under material examined of Ch. attae ).

Figures

Fig. 1. General aspect of a stylised female of Cholovocera Victor, 1838. A. Dorsal view. B. Ventral view. Abbreviations: see Material and methods. Scale bar = 0.5 mm.

Fig. 2. Mouth parts, antenna and distal metatarsomere of Cholovocera formiceticola (Rosenhauer, 1856). A. Labrum, dorsal view. B. Epypharynx, ventral view. C. Left antenna, ventral view. D. Left maxilla, ventral view. E. Left mandible, dorsal view. F. Right mandible, dorsal view. G. Labium, ventral view. H. Hypopharynx, ventral view. I. Distal metatarsomere, dorsolateral view. Scale bar = 0.1 mm.

Fig. 3. Head. A. Tentorium, ventral view. B. Tentorium, lateral view. C. Hind wing of Cholovocera formiceticola (Rosenhauer, 1856). D. Stylised aedeagus, ventral view. Abbreviations: see Material and methods. Scale bars = 0.1 mm.

Fig. 24. A. A syntype of Cholovocera formicaria Victor, 1838, dorsal view (courtesy of K.V. Makarov). B. Same specimen, ventral view (courtesy of K.V. Makarov). C. Holotype of Ch. brevicornis Johnson, 1977 (= Displotera beloni (Wasmann, 1899)), dorsal view. D. Same specimen, ocular area, lateral view. E. Ocular area of Ch. formiceticola (Rosenhauer, 1856) (Lisbon), lateral view. F. Aedeagus of Ch. formicaria major, lectotype, ventral view. G. Same specimen, lateral view. H. Aedeagus of Co punctata sardoa, lectotype, ventral view. I. Same specimen, lateral view. Scale bars: A–C = 0.5 mm; D–I = 0.1 mm.

Fig. 4. Prosternal processes. A. Cholovocera afghana Johnson, 1977. B. Ch. attae (Kraatz, 1858). C. Ch. balcánica (Karaman, 1936). D. Ch. gallica (Schaufuss, 1876). E. Ch. formicaria Victor, 1838. F. Ch. formiceticola (Rosenhauer, 1856). G. Ch. occulta sp. nov. H. Ch. punctata (Märkel, 1845).

Fig. 5. Terminal abdominal segments of Cholovocera formiceticola (Rosenhauer, 1856), ♀. A. Last visible ventrite, ventral view. B. Gonocoxites, paraprocts and proctiger, ventral view. C. Tergite 8, dorsal view. D. Sternite 8, ventral view. E. Proctiger, dorsal view. Abbreviations: see Material and methods. Scale bar = 0.1 mm.

Fig. 6. Terminal abdominal segments of Cholovocera formiceticola (Rosenhauer, 1856), ♂. A. Last visible ventrite, ventral view. B. Left hemitergite, dorsal view. C. Tergite 8, dorsal view. D. Spiculum gastrale, ventral view.E. Sternite 8, ventral view. F. Hemitergites and proctiger, dorsal view. Scale bar = 0.1 mm.

Fig. 7. Spermathecae, lateral view. A. Cholovocera afghana Johnson, 1977. B. Ch. balcánica (Karaman, 1936). C. Ch. occulta sp. nov. D. Ch. gallica (Schaufuss, 1876). E. Ch. formicaria Victor, 1838. F. Ch. formiceticola (Rosenhauer, 1856). G. Ch. punctata (Märkel, 1845). Abbreviations: See Material and methods. Scale bar = 0.1 mm.

Fig. 8. Cholovocera Victor, 1838 feeding, parasites and commensals. A. Nest chamber of Messor barbarus (Linnaeus, 1767) with seeds and one specimen of Ch. formiceticola (Rosenhauer, 1856).B. Gut content: particulate material. C–D. Fungal spores. E. Hyphae. F. Arthropod remains. G. Parvomyces cf. merophysiae Santamaria, 1995 attached to a leg of Ch. formiceticola (Rosenhauer, 1856). H. Specimen of Parvomyces cf. merophysiae Santamaria, 1995. I. Malpighian tubules of Ch. formiceticola (Rosenhauer, 1856) with cyst of parasitic amoebae. J. Cysts enlarged.K. Rhizoglyphine mite, phoretic on Ch. punctata (Märkel, 1845), ventral view. L. Same mite, lateral view. Scale bars: A–F = 20 µm; G–L = 30 µm.

Fig. 9. Known geographical distribution of the species ofCholovocera Victor, 1838.A. Ch. formiceticola (Rosenhauer, 1856) (red dots) and Ch. gallica (Schaufuss, 1876) (yellow dots). B. Ch. punctata (Märkel, 1845) (red dots) and Ch. occulta sp. nov. (yellow dots). C. Ch. balcanica (Karaman, 1936) (red dots), Ch. attae (Kraatz, 1858) (yellow dots), Ch. formicaria (dark blue dots) and Ch. afghana Johnson, 1977 (orange dot).