Monoicomyces britannicus Thaxt.

MB#192361

Figs 82, 83A

Proceedings of the American Academy of Arts and Sciences 35: 413 (Thaxter 1900, as M. brittanicus). –

Type: “ On Homalota insecta Thorn., British Museum, No. 454, Hammer smith, England. On superior surface of abdomen”; FH.

Diagnostic features

Primary appendage usually branched once above the basal cell, rarely simple, with the dorsal branch deeply blackish-brown near the base. Cell III inflated, large, pale, in contact with cell I and separated from cell II by a ± vertical or oblique septum (Fig. 82C–D). Two to four secondary appendages for each antheridium. Each antheridium including four phialides (Fig. 82E–F, arrows). [Detailed descriptions: Thaxter 1908; Santamaria 1989]

Distribution and hosts

Reported on Atheta (in part as Homalota Mannerheim, 1831) from Europe: Finland, France, Germany, Italy, Poland, Spain, United Kingdom, Russia (Santamaria et al. 1991), Hungary (Bánhegyi et al. 1985), Belgium (De Kesel & Haghebaert 1991), Greece (Castaldo et al. 2004), Latvia (De Kesel & Krastina De Kesel 2006), Sweden (Huggert 2010), and the Netherlands (Haelewaters et al. 2014).

Collections examined from Denmark

On Acrotona aterrima (Gravenhorst, 1802) (Col. Staphylinidae Aleocharinae) DENMARK – Nordøstjylland (NEJ) • Vandplasken ved Kaersgård Strand; 57°31.199′ N, 9°53.070′ E; NJ57; 21 Nov. 2017; JP 806; JP det.; ZMUC C-F-123301 .

On Acrotona fungi (Gravenhorst, 1806) (Col. Staphylinidae Aleocharinae) DENMARK – Nordvestsjaelland (NWZ) • Flyndersø ved Dybesø; 55°58.151′ N, 11°45.621′ E; PH60; 4 Nov. 2017; JP 723; JP det.; ZMUC C-F-123216 .

On Acrotona pseudotenera (Cameron, 1933) (Col. Staphylinidae Aleocharinae) DENMARK – Østjylland (EJ) • Kjellerup; 56°17.644′ N, 9°25.850′ E; NH23; 16 Feb. 2018; JP 975; JP det.; ZMUC C-F-123482 . – Lolland, Falster, Møn (LFM) • Hobyskov; 54°44.069′ N, 11°15.296′ E; PF46; 7 Jan. 2018; JP 956; JP det.; ZMUC C-F-123462 . – Nordvestjylland (NWJ) • Legind; 56°45.832′ N, 8°48.782′ E; MH89; 19 Oct. 2008; JP 80; JP det.; ZMUC C-F-122555 . – Sydsjaelland (SZ) • Gammel Kalvehave; 54°59.745′ N, 12°8.232′ E; UA19; 27 Apr. 2018; JP 1087; JP det.; ZMUC C-F-123605 .

On Acrotona sp. (Col. Staphylinidae Aleocharinae) DENMARK – Nordøstsjaelland (NEZ) • Brønshøj; 55°42.234′ N, 12°30.135′ E; UB47; 2 Jul. 2012; JP 38; JP det.; ZMUC C-F-122513 .

On Aloconota sulcifrons (Stephens, 1832) (Col. Staphylinidae Aleocharinae) DENMARK – Østjylland (EJ) • Klostermølle; 56°2.432′ N, 9°41.629′ E; NH41; 14 Feb. 2019; JP 1349; JP det.; ZMUC C-F-123888 .

On Atheta longicornis (Gravenhorst, 1802) (Col. Staphylinidae Aleocharinae) DENMARK – Nordvestsjaelland (NWZ) • Klintebjerg ved Klint; 55°57.351′ N, 11°34.463′ E; PH60; 1 May 2016; JP 56; JP det.; ZMUC C-F-122531. – Sydsjaelland (SZ) • Gammel Kalvehave; 54°59.745′ N, 12°8.232′ E; UA19; 24 Mar. 2018; JP 1012; JP det.; ZMUC C-F-123519 .

On Atheta volans (Scriba, 1859) (Col. Staphylinidae Aleocharinae) DENMARK – Sydsjaelland (SZ) • Tryggevaelde Å ved Varpelev; 55°21.055′ N, 12°15.877′ E; UB23; 6 Jan. 2018; JP 973; JP det.; ZMUC C-F-123480 .

Remarks

First record from Denmark. Very often, cell II is difficult to distinguish because it is flat and wedgeshaped. In front view it appears almost concealed behind cell I and below cell III (Fig. 82D). In side view, the disposition of cells I, II and III is a characteristic that easily distinguishes M. britannicus from M. homalotae (Fig. 82C–D).

Thaxter (1908), when describing M. britannicus, wrote “too nearly related to M. homalotae, and may prove to be only a variety” and “general structure as in M. homalotae, the third cell of the primary appendage suffused with blackish brown, somewhat constricted below”. Likely, Thaxter refers to the third cell of the receptacle or to the basal cell of the appendage.

Distinctiveness of M. britannicus from M. homalotae was questioned by Majewski (1994b) who considered the differences between the two species irrelevant and included M. britannicus among the synonyms of M. homalotae describing the latter with very broad characteristics.

The first author (SS) has studied the types of both species several years ago; in 1990 the type slide of M. britannicus (labelled FH2352) was borrowed from FH (Fig. 83A). The type slide contained only one thallus, as illustrated by Thaxter (1908). Although the photographs of the types are old and of low quality, we reproduce them here for its documentary interest (Fig. 83A–B). An extended discussion appears below under the remarks of M. homalotae .