Picrotus Sharp, 1886

Gimmel, Matthew L. & Leschen, Richard A. B., 2022, Revision of the genera of Picrotini (Coleoptera: Cryptophagidae: Cryptophaginae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 62 (1), pp. 61-109 : 104-105

Picrotus Sharp, 1886

( Figs 68, 69 )

Picrotus Sharp, 1886: 394 . Type species: Picrotus thoracicus Sharp, 1886 , by monotypy.

Diagnosis. This genus is easily distinguished from other Picrotini by the broad body form and the extremely wide lateral bead of the pronotum ( Figs 68, 69 ). Additionally, the body is virtually glabrous dorsally and the antennal club is composed of only two antennomeres.

Redescription. Length 1.05–1.27 mm. Body form ( Figs 68, 69 ) extremely short, stout, ovate, with extremely short, extremely sparse, inconspicuous decumbent setae dorsally, erect or suberect setae totally absent; weakly to strongly bicolored. Head without tempora; vertex with (undescribed species) or without ( P. thoracicus ) ridge, temporal depression immediately anterior to ridge lacking; band of reticulate sculpture lacking. Frontoclypeus not projecting laterally anterior to antennal insertions; raised portion of frons between antennal insertions not strongly constricted, as wide as or wider than antennal club. Transverse ridge above antennal insertions present ( P. thoracicus ) or absent (undescribed species). Eye small, conical, contacting antennal cavity ( P. thoracicus ) or not (undescribed species); interfacetal setae absent. Antenna inserted into large cavity on head; antennal club consisting of 2 antennomeres; antennomere 9 equal in width to antennomere 8 or almost imperceptibly wider. Mandible with apex bifid, subapical serrations present. Maxillary palpomere 4 subequal in length to 3; palpomere 4 conical but not subulate. Gena without antennal groove; genal spines broadly to narrowly rounded, right to obtuse. Gular sutures present, incomplete, not reaching occipital foramen. Pronotum not explanate, not constricted at base, equal in width to base of elytra, widest in basal half, distinctly transverse; anterior angles weakly to strongly projecting anteriorly (extending anterior to cervical foramen of prothorax), without a distinct platform but (in undescribed species) with slight swelling associated with small, flat glandular area; lateral carina present and complete, not bearing setigerous tubercles, width of lateral bead about as wide as antennal club; disc with weak ( P. thoracicus ) or without transverse basal impression extending across width of pronotum; paramedial carinae and paralateral plicae absent; posterolateral angles obtuse (undescribed species) to narrowly rounded, acute, and projecting posteriorly ( P. thoracicus ). Prothoracic hypomeron fused to prosternum ( P. thoracicus ) or separated by suture (undescribed species). Prosternum with anterior margin on same plane as disc; prosternal process with lateral marginal beads weakly (undescribed species) to strongly ( P. thoracicus ) present, parallel-sided, connected across apex, process with ( P. thoracicus ) or without (undescribed species) narrow longitudinal depression medially, process expanded (undescribed species) or not ( P. thoracicus ) apically, apex truncate and not crenulate, lacking setae; procoxal cavity with (undescribed species) or without ( P. thoracicus ) anterolateral notch. Scutellar shield clearly visible and transverse (undescribed species) or mostly hidden except for extreme apex ( P. thoracicus ). Elytron lacking humeral tooth, lacking subbasal and subapical impressions; subapical gape absent; punctation extremely sparse, fine, virtually absent ( P. thoracicus ) to coarse, densely concentrated in scutellar region (undescribed species); vestiture originating in punctures, uniformly short and recumbent. Hind wing vestigial. Mesoventrite with mesoventrital cavity bowllike, glabrous, flanked by sharp carinae. Mesanepisternal pit absent. Metaventrite with short, crenulate postcoxal lines; discrimen absent, posterior notch of metaventrite absent. Metendosternite with anterior tendons widely separated or absent. Tarsi 5-5- 5 in female, 5-5- 4 in male; tarsi moderately slender to compact, tarsomere 5 as wide ( P. thoracicus ) or wider as preceding tarsomeres in lateral view; pro- and mesotarsomere 4 asetose; mesotarsomere 3 not lobed, with few setae; mesotarsomeres 1–3 of subequal to equal lengths with 1 slightly shorter ( P. thoracicus ) or longer than 2, 3 and 4 equal, 4 slightly shorter than 3, mesotarsomere 5 equal to ( P. thoracicus ) or shorter than tarsomeres 1–4 combined. Abdominal ventrites free ( P. thoracicus ) or 1–3 solidly fused with sutures nearly obliterated (undescribed species), with medial calli absent, lateral calli present or absent, intersegmental crenulations absent; ventrite 1 with intercoxal process broadly rounded, with postcoxal lines absent; medio-basal thickenings of ventrites 3–5 absent; apex of ventrite 5 with crenulations. Abdominal spiracles on segment VII with openings present and not larger in diameter than spiracle VI, texture smooth and atrium rounded and saclike. Aedeagus with tegminal strut absent, tegminal arms contiguous; parameres fused to phallobase and broadly at their bases and separated at the apex ( P. thoracicus ) or separate and articulated to phallobase with inner surface concave (undescribed species), fused parameres combined about 1.2× wider than long ( P. thoracicus ) or about 3× longer than wide; apices multisetose; attachment point to phallobase not constricted, interparameral process present (undescribed species) or absent; basipenis 4× (undescribed species) to about 8× ( P. thoracicus ) longer than distipenis, without median carina; distipenis rectangular and transverse and about 1.2× wider than long ( P. thoracicus ) to elongate and about 2× longer than wide (undescribed species), outer rims not crenulate, lateral lobes narrowly to widely ( P. thoracicus ) separated, symmetrical; internal sac with a pair of thin sclerites that extend 2/3 the length of the sac ( P. thoracicus ) or a single arrow-shaped plate (undescribed species).

Remarks. There are three species in this New Zealand genus (Chen & Leschen, in prep.), one described ( Fig. 68 ), one from the southeastern part of the North Island that is undescribed and very similar to P. thoracicus , and another ( Fig. 69 ) very different from the other two having distinctive characters noted above in the description, such as the eye contacting antennal cavity, connate abdominal ventrites 1 and 2, a widened tarsomere 5, a rugose body form, and an unusual arrow-shaped plate in the internal sac that suggest it may be a separate genus. Despite these differences, we consider the genus monophyletic based on the characters in the diagnosis.

Biology. Specimens of Picrotus are found in leaf litter, and P. thoracicus may be rather abundant, whereas the remaining two undescribed species are known by significantly fewer specimens.

Distribution. New Zealand.

Included species (1+2). Picrotus thoracicus Sharp, 1886 ; two undescribed species from New Zealand.

Figures

Figs 64–72. Habitus of species of Picrotini. 64 – Ostreacryptus n. sp. 4 (Australia: NSW, Tas, Vic); 65 – Ostreacryptus n. sp. 5 (New Zealand); 66 – Papuacryptus striatopunctatus sp. nov.; 67 – Paragnetaria slipinskii sp. nov.; 68 – Picrotus thoracicus Sharp, 1886; 69 – Picrotus n. sp. 1 (New Zealand); 70 – Thortus amoenus (Broun, 1912); 71 – Thortus ovalis Broun, 1893; 72 – Thortus n. sp. 1 (New Zealand: Auckland Islands). Scale bars = 1 mm. Abbreviations: pc = paramedial carina.