Ichneumon xanthorius [1,2,3,4,5] is an uncommon wasp that occurs throughout the Netherlands .
In some litereature the species is referenced with its old name Amblyteles equitatorius.
The species is active from April to August with a peak for males in June and July, and for the females in April and May .
The species overwinters as larva and has possibly more generations per year . The larvae pupate in the ground in May .
Development take on average 30 days for females and 26 days for males .
3. PARASITIC RELATIONS
I. xanthorius is a polyphagous  endoparasitoïd on moths from the Noctuidae family , especially on cocoons in the ground, on the following species occurring in the Netherlands :
| –Noctua comes |
–Noctua fimbriata 
–Xestia baja 
–Xestia ditrapezium 
–Xestia stigmatica (syn. X. rhomboidae ) 
–Xestia trianglum 
The following hosts have been observed in the garden:
|– Lesser yellow underwing (Noctua comes) |
It is a large wasp with a length of 15mm
(different internet sites provide a length of 15mm for males and females. The length of the female is specified as 13 – 14 mm in the Perkins key  ).
The characteristics of I. xanthorius are :
1. Mandible with one tooth
2. Thyridia short as very narrow transverse band
3. Gastrocoelus quite large, width at least as wide as distance between gastrocoeli
4. Tergites 5, 6 and 7 with yellow marks
5. Tergiten 1 to 4 with wide yellow band apically
7. Coxa hindleg with yellow spot on top
8. Thigh (femur) hindleg black
9. Head with temples strongly narrowing behind eyes
1. Narrow species
2. Postpetiole, upper part of 1st tergite, yellow
3. Hind leg coxa with yellow spot dorsally
4, Hind leg coxa large 
5. Femur, hind leg yellow with lower halve black
6. Tibia, hind leg black lower edge
7. Clypeus truncated
References1 Nederlands Soortenregister
2 BROAD, Gavin. Identification key to the subfamilies of Ichneumonidae (Hymenoptera). Natural History Museum, London, 2011.
3 PERKINS, James F. Hymenoptera: Ichneumonoidea, Ichneumonidae, key to subfamilies and Ichneumoninae.
4 PERKINS, John Frederick. Hymenoptera, Ichneumonoidea: Ichneumonidae I.[and] Ichneumoninae II, Alomyinae, Agriotypinae and Lycorininae.
5 Albert de Wilde, Insecten fotosite ahw.me, Wespen
6 HINZ, Rolf; HORSTMANN, Klaus. Über Wirtsbeziehungen europäischer Ichneumon-Arten.
7 Vlinderstichting.nl, "Vlinders", De Vlinderstichting