Euura gregaria
Creators: name: Prous, Marko
name: Liston, Andrew
name: Monckton, Spencer K.
name: Kramp, Katja
name: Vårdal, Hege
name: Vikberg, Veli
name: Heibo, Erik
name: Mutanen, Marko
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Tenthredinidae
Euura
Euura gregaria

description: 167 Euura gregaria (Marlatt, 1896)
Figs 188, 417
Pachynematus gregarius Marlatt, 1896b: 256–257. Syntypes 1 ♀ 1 ♂ (USNM), not examined. Type localities: USA, New Hampshire and New Jersey.
Pontania decrepita MacGillivray, 1921b: 33. Syntype ♀, not examined. Type locality: USA, New York, Ithaca.
Pachnematus [sic!] rarus MacGillivray, 1921b: 30–31. Syntype ♀, not examined. Type locality: USA, Maine, Orono.
Pachynematus dentatus Lindqvist, 1937: 132–135. Lectotype designated below. Syn. nov.
Diagnosis
Its colouration (at least labrum, clypeus, tegula, legs, and abdomen ventrally pale), size (female 4.5– 5.5 mm, male 3.0– 4.5 mm), and characteristic shape of the subapical tooth of claws (far removed from apical tooth, about as long as apical tooth, and area between the teeth forming a semicircle) help in identifying the species. In the male, the combination of black pronotum (posteriorly pale in female) and pale tegula further helps in recognizing the species. Size (1 mm) and shape of the penis valve is most similar to that in the E. dolichura group (0.7–0.8 mm) and E. microphyes (0.8 mm), but its claws and colouration should enable separation of E. gregaria from these taxa. We do not consider the small differences between gregarius and dentatus listed by Wong (1967) to be significant and treat them as synonymous. While COI divergence between one North American (USA) specimen and Finnish specimens is 3.3–4.4% (810 bp) or 2.1–5.2% (420–423 bp of overlapping barcoding region), the nuclear divergence is only 0.2% (based on 1774 bp of NaK and EF1a F2), corresponding to an average haplotype divergence for Euura female individuals.
Female
4.5–5.5 mm. Head black or extensively brown around eyes, antenna black, labrum and clypeus pale; thorax black, pronotum black, tegula pale; pterostigma pale; abdomen dorsally black, ventrally pale, valvula 3 black; legs nearly entirely pale, except brown hind tarsi and apex of hind tibia. Claws with large subapical tooth, forming almost a semicircle with curved apical tooth; valvula 3 in dorsal view short and gradually tapering.
Male
3.0– 4.5 mm. Differences from female: similar to female, but sometimes also the mesepisternum is pale and partly the abdomen dorsally.
Type material examined
Lectotype Pachynematus dentatus, here designated
FINLAND – Uusimaa • ♀; Helsinki, Munksnäs [Munkkiniemi]; 60.22° N, 24.89° E; 28 Jul. 1937; E. Lindqvist leg.; MZH, http://id.luomus.fi/GL.2443.
Host plants
Salix phylicifolia (Lindqvist 1937), S. myrsinifolia, S. pentandra.
Genetics
COI
Based on 5 specimens, maximum within-species distance is 4.41% and the nearest neighbour, diverging by a minimum of 6.28%, is Euura salicis. When secondary intraindividual COI variants are also included, maximum within-species distance is 5.32% and the nearest neighbour, diverging by a minimum of 6.08%, is E. salicis. A specimen from North America (E4) is 2.1–5.2% different from the European specimens (based on 420–423 bp of overlapping barcoding region).
Nuclear
Based on 2 specimens, maximum within-species distance is 0.03% (0.02% based on haplotypes of individual females). The nearest neighbour, diverging by a minimum of 2.49%, is Euura jugicola.
Distribution and material examined
Palaearctic. Specimens studied are from Finland, and the USA.
description: Published as part of Prous, Marko, Liston, Andrew, Monckton, Spencer K., Kramp, Katja, Vårdal, Hege, Vikberg, Veli, Heibo, Erik & Mutanen, Marko, 2025, West Palaearctic species of Euura Newman, 1837 (Hymenoptera, Tenthredinidae), pp. 1-377 in European Journal of Taxonomy 977 on pages 116-117, DOI: 10.5852/ejt.2025.977.2799, http://zenodo.org/record/15019574