Achaius CAMERON

A. M, 2011, Illustrated key to the genera of the subtribe Amblytelina of Palaearctic (Hymenoptera, Ichneumonidae, Ichneumoninae, Ichneumonini), Linzer biologische Beiträge 43 (1), pp. 597-711 : 636-638

4. Achaius CAMERON

Achaius CAMERON 1903 - Ann. & Mag. Nat. Hist. 12: 266.

Type species: Achaius flavobalteatus CAMERON.

Achaius: HEINRICH 1965 - Entomol. Ts. Agr. 86, 1-2: 111.

Achaius: RASNITSYN 1981 - Opr. Faun. SSSR 3 (3): 568, 618.

D i s t r i b u t i o n: Palaearctic, Oriental Region (highland).

I n t r o d u c t i o n:

Genus is close to Diphyus KRIECHBAUMER (= Pseudamblyteles ASHMEAD). The slightly elevated and not striated middle field of postpetiolus, more long propodeum with approximately equal horizontal and slanted parts, absence of costulae and transformation of external carina of area dentipara to short tooth (denticle), without changing of direction (tooth is not bent upwards) are characteristic for species of the genus. Surface of head, thorax and base of abdomen are dull on the larger part. Hypopygium of male is oblong to apex, without narrow long process. Tibiae are with white rings.

M o r p h o l o g y:

F l a g e l l u m: Long, slender, strongly attenuated and pointed toward apex, behind middle not widened, with white annulus; in males ribbed ventrally behind middle with distinct narrow tyloides.

H e a d: Head contour from front uniformly narrowed downwards, vertex from lateral straightly sloping behind ocelli; temples from above strongly roundly narrowed behind eyes; mandibles normal, narrow, the most part parallel-sided, upper tooth longer than lower one; clypeus only just convex with straight front margin; middle field of face distinctly elevated and separated by slight impressions from clypeus and lateral fields. Most part of head surface dull.

T h o r a x: Mesonotum from moderately to strongly convex, only just longer than width, notauli impressed only at base, surface of mesonotum densely punctured, dull; sternauli of European species only just marked in a form of broad impressions; axillary tongue practically not expressed; scutellum high elevated above postscutellum and roundly fall backwards with slightly convex horizontal part, laterally not carinated, with smooth dorsal surface. Hind margin of metanotum with projections. Propodeum from lateral angle-shaped; horizontal part of propodeum approximately equal to length of area posteromedia in middle; basal area of palaearctic species short and deep and without tubercle; area superomedia usually wider than lateral fields, without costula, in females longer than width; external carina of area dentipara not changing direction transform to short tooth (denticle); spiracles long, slit-shaped.

L e g s: Long and slender. Hind coxae of females without scopa.

W i n g s: Areolet pentagonal; nervulus postfurcal; radius slightly sinuous at apex.

A b d o m e n From above longish-oval, of females amblypygous, seventh tergite far protrude from under sixth on its length. Middle field of postpetiolus delicately irregularly-wrinkled to smooth with sparse punctures, not striated. Gastrocoeli not big, not deep with distinct thyridia, narrower than interval; interval between thyridia delicately longitudinally striated; surface of anterior tergites coriaceous. Sternites 2-3 with longitudinal fold; hypopygium overlap slit of ovipositor, with blunted apex. Hypopygium of males elongated to apex at central part, but without long process.

C o l o r a t i o n: Body black with characteristic white pattern. European species with broad spots on frontal orbits, rings on tibiae and spots on apical tergites of abdomen. White pattern in males more rich, including apical bunds on anterior tergites of abdomen.

S i z e: Palaearctic species 11-17 mm.

B i o l o g y a n d e c o l o g y:

H o s t s: The 5 species of Noctuidae ( Apamea crenata HUFN. , Cerastis rubricosa DEN. et SCHIFF. , Diarsia brunnea DEN. et SCHIFF. , Plusia festucae L., Polia nebulosa HUFN. ), 1 species of Saturniidae ( Saturnia pavonia L.) from Western Palaearctic and 1 species of Lasiocampidae ( Dendrolimus spectabilis BUTLER ) from Japan are known from the literature, noted as the hosts of only one species – Achaius oratorius (F.) ( HERTING 1976; RASNITSYN1981).

S p e c i e s c o m p o s i t i o n a n d a b u n d a n c e: The genus is presented in region of researches by only one species – A. oratorius – the most mass representative of subtribe. Abundance of this species in the nature along with little number of species of a genus, leads genus Achaius to the first place according to indicator of abundance among Amblytelina and on 4th place among genera of Ichneumoninae St. in the region.

B i o t o p i c a l d i s t r i b u t i o n: The genusis presented in the majority of the open and forest ecosystems. 92 % from total number of collected specimens are focused on forest ecosystems and 8 % on open ones (meadows and personal plots). Among ecosystems Achaius in the greatest quantity is presented in pine forests, polytric (Pinetum pleurozosum) and bog moss (P. sphagnosum) – 38 %, and among deciduous ones, in alder forests (Alnetum urticosum) – 34 %.

S e a s o n a l a c t i v i t y a n d h i b e r n a t i o n: Activityof Achaius ’ females is observed from May till October with peak of activity in July. The period of activity of males is more compressed and observed from June till August with sharp peak in July. The course of seasonal activity indicates to presence of only one generation and is characteristic for the species which females hibernate on imaginal stage. References on hibernation of females A. oratorius (F.) are given by A. RASNITSYN (1964).