Notes on Eopsis beaumonti Benson 1959 (Hymenoptera, Tenthredinidae)

This species was first found in June 1959 by Dr. J. de Beau­ mont in the Swiss Jura, Vaud, Les Pleiades (1200 m) and described in the same year by Benson (1959) as a member of the subfamily Tenthredininae, because vein Sc+R in the forewing is slightly curved apically and because M joins Sc+R at a distance from intersection of Rs+M with Sc+R. The first character is typical for Tenthredininae, but in Eopsis is rather variable, this part of Sc+R being slightly curved to nearly straight. Taeger (1986) gave a detailed redescription, and transferred Eopsis to the tribe Allantini of the subfamily Allantinae. Lacourt (1999) placed it in his catalogue in a tribe Eopsini, but notes in the page of Errata that Eopsini should read Allantini. Two years later (Lacourt 2001) he listed it once more as a member of the Allantini. Nevertheless, the endophagous development and unusual morphology of the larva seem to support its placement in a separate tribe. It is noteworthy that though this species is quite conspicuous and characteristic in colour, no specimens collected before the middle of the 20th century have been detected in any collections.

This species was first found in June 1959 by Dr. J. de Beau mont in the Swiss Jura, Vaud, Les Pleiades (1200 m) and described in the same year by Benson (1959) as a member of the subfamily Tenthredininae, because vein Sc+R in the forewing is slightly curved apically and because M joins Sc+R at a distance from intersection of Rs+M with Sc+R. The first character is typical for Tenthredininae, but in Eopsis is rather variable, this part of Sc+R being slightly curved to nearly straight. Taeger (1986) gave a detailed redescription, and transferred Eopsis to the tribe Allantini of the subfamily Allantinae. Lacourt (1999) placed it in his catalogue in a tribe Eopsini, but notes in the page of Errata that Eopsini should read Allantini. Two years later (Lacourt 2001) he listed it once more as a member of the Allantini. Nevertheless, the endophagous development and unusual morphology of the larva seem to support its placement in a separate tribe. It is noteworthy that though this species is quite conspicuous and characteristic in colour, no specimens collected before the middle of the 20th century have been detected in any collections.
Since its description E. beaumonti has been recorded from the following countries: France: Jura, Lamoura 1200 m; Hautes-Alpes; Savoie; Loire; Haute-Loire 1150 m; M assif Central, 850-1200 m, Puy-de-Dôme (Lacourt, 1976, 1985, 2001and Noblecourt, 2006. Czech Republic: Giant Mts. (Benes, 1984(Benes, , 2012(Benes, , 2013; Jizerské hory Mts. (Macek 2009). Germany: Harz (Taeger 1986); Bavaria (Blank et al. 2001); Hesse (Lohr 2014). Slovakia: High Tatra Mts., Javorina (Roller 1999); Zadna Javorova dolina (valley) up to 1600 m (Roller & Haris 2008). Belgium: No exact locality given (Mol 2002). Poland: Giant Mts. (Benes 2012(Benes , 2013 Unlike other representatives of the subfamily Allantinae, the larvae of Eopsis are endophagous. They bore in the stems of Bistorta major and are conspicuously adapted to endophagous life. Oviposition takes place into an ochrea at the base of an internode. The 1st instar larva bores immediately after eclosion into the stem above the node and starts to feed upwards towards the medulla. Oviposition apparently continues at the same locality for a longer time, as up to three larvae of different instars were found in the same stem, from the eldest one (3rd instar) in the basal internode (Fig. 2), to a freshly hatched larva in the terminal one. Data on Rumex as a host plant (Benes, 1984, Liston, 1997) are apparently erroneous, as a female oviposited in the laboratory into Rumex alpinus but the larvae developed only for a short while, then perished. Furthermore, when the larvae were transferred in the laboratory from Bistorta to Rumex, they admittedly started to bore into the pith, but died soon afterwards. They are apparently monophagous, as no larvae were found on Bistorta vivipara (in the Belanske Tatry Mts.) close to the stands of infested Bistorta major.
Infested plants are usually easily recognized by a fading, rather yellowish than pink coloration of the flower spike, which is usually also smaller. The larvae have four feed ing instars. Nothing definite is known about formation of a cocoon, but it is probable that the mature larvae bore into dry stems or bark to pupate, in the same way as most other Allantinae.
Morphological adaptations o f the larva.
Some characters of Eopsis are shared with other endopha gous larvae, such as the nearly glabrous integument without visible setae and the feebly developed prolegs.
On the other hand, Eopsis possesses a conspicuous adap tation of the tracheal system that has not been found in any other sawfly larva. While in other sawfly larvae the spiracles are on thoracic segments 1 (and often also 3), and abdominal segments 1-8, the prothoracic ones being the biggest, in Eopsis the spiracles are present also on segment 10. A terminal pair of spiracles is located laterally in the basal part of the suranal plate and these spiracles are about twice as long as the prothoracic and abdominal ones. Further, the tracheal trunk is here also much wider than in the thoracic equivalent. The tergum of the anal segment is flat, more strongly sclerotized than other parts of the body, laterally and posteriorly with brownish warts, and is used as a cork to close an opening in the stem. In the 1st and 2nd instar larvae, the prolegs are well developed and the fine chaetotaxy of the trunk is visible (against a black background). Pale setae on poste rior edge of subanal plate dense and about as long as antennae; setae on abdominal segments sparse.