Foersterella Dalla Torre

Hansson, Christer, 2016, The European species of Foersterella Dalla Torre (Hymenoptera: Tetracampidae), including the description of two new species, Zootaxa 4137 (4), pp. 561-568 : 562

Foersterella Dalla Torre

Hyperbius Förster, 1878: 58 . Type species: Tetracampe flavipes Förster (1841) , by original designation and monotypy. Name preoccupied by Hyperbius Stål (1867) .

Foersterella Dalla Torre, 1897: 86 . Replacement name.

Species identification. Species of Foersterella are characterized by a short petiole that is wider than long, a very long antennal pedicel that is 2.3–2.5× as long as wide and at least twice as long as the first flagellomere, an antennal clava that usually is distinctly wider than the first flagellomere, and by an enlarged male scape that is about twice as long as wide and pale yellow. They are morphologically very similar to one another, displaying differentiating characters mainly in the male antenna and to some extent in the female gaster. Thus, without additional information, such as host or molecular data, it is difficult to associate females and males of the same species in this genus. When F. erdoesi was described by Bouček (1958) he unknowingly associated female and male incorrectly. The female and male included in the description belong to two different species, which became clear when I was able to examine a small series (2♀, 3♂ in BMNH) of reared specimens from Cassida viridis from Romania. Females of this series agree well with the original description of F. erdoesi whereas the males are different from the male described as F. erdoesi . Bouček did not have access to reared material so his mistake is understandable. The holotype of F. erdoesi is a female so this is the name-bearing sex. The antennal flagellum of the male described as F. erdoesi is different from that of the true F. erdoesi male in that it is completely dark ( Figs 4 , 10 ), whereas it is bicoloured in F. erdoesi ( Figs 2 , 7 ) and F. reptans ( Figs 3 , 8 ), the other European species. The male of F. erdoesi sensu Bouček is here described as a new species.

Females identified as F. erdoesi differ from other females examined here as indicated in the key below. The other females (101 females examined from Austria (2), Czech Republic (7), England (20), France (7), Hungary (1), Slovakia (1), Spain (2), and Sweden (61), in BMNH and MZLU), do not show any noticeable morphological differences. In view of that there are three additional species apart from F. erdoesi , it is difficult to assign a species identity to these females. The females of these three species therefore have to remain unassociated until biological and/or molecular information facilitates their species association to males.

Figures

FIGURES 1 – 6. 1 – 4, Foersterella spp., habitus in lateral view: 1, F. angusticornis sp. nov., male holotype, specimen length 1.1 mm; 2, F. erdoesi Bouček, male non-type from Sweden (Skåne), specimen length 1.3 mm; 3, F. reptans (Nees), male non-type from Sweden (Skåne), specimen length 1.1 mm; 4, F. fuscicornis sp. nov., male holotype, specimen length 1.2 mm. 5 & 6. Head, frontal view, males: 5, F. angusticornis, holotype; 6. F. erdoesi, non-type from Sweden (Skåne).

FIGURES 7 – 13. Foersterella spp. 7 – 10, antenna, lateral view, male: 7, F. erdoesi Bouček; 8, F. reptans (Nees); 9, F. angusticornis sp. nov.; 10, F. fuscicornis sp. nov. 11, Foersterella sp., female, head and antennae, lateral view. 12 & 13, gaster, dorsal view, female: 12, Foersterella sp.; 13, F. erdoesi.