(Figs 1, 5, 7)

Type material. Holotype ♀. Sardinia (Sassari province)/ Lake Baratz, Malaise trap /40˚ 40’, 61 N – 8˚16’, 64 E, 30 m,/ 15–30.VIII.2002 / F. Strumia legit// (FSC).

Paratypes: same data as holotype but 18.VIII–3.IX.2003, 1 ♀ (FSC), same data as holotype but 16–28.VII.2004, 1 ♀ (MSNPU, collection registration number: IME-12008).

Etymology. The name refers to the type locality of the new species and must be treated as a Latin adjective.

Diagnosis. Distinctive features of the new species (Fig. 1) are the shape of the distal margin of TIII, the absence of the pronotal lateral carina, the carina around the compound eye, and the two isolated and not touching black spots on STII, that are, on the contrary, touching or fused together in all other studied species of the genus (see also the key at end of this paper).

Description. Body length 4.3 (paratype) to 5.9 mm (holotype and paratype).

Colour. Body blue-green as in other species of the genus. Dark blue at base of central part of mesonotum, between ocelli and at base of TII; body pubescence short and white. Fore wings slightly brown-stainted. Antenna black in colour with pedicel and FI metallic green. Legs metallic green; first tarsomere of anterior leg metallic green as tegulae.

Head. Elevated carina all around compound eye (Fig. 7). Facial cavity deep, finely, irregularly and transversally striate; malar space as long as FII. Mandible simple, without additional teeth.

Thorax. Pronotum lacking lateral carina and with a weak groove in the middle of anterior edge. Punctures on mesonotum and scutellum large with smooth shining areas and smaller punctures in between. Radial cell of fore wings narrow, long and closed. Propodeal angle obtuse, pointing backward.

Abdomen. Anterior declivity of TI with two grooves delimiting two anterior humps. Punctures on TII smaller than on thorax, becoming smaller distally. TIII saddled in shape, with smaller punctures than TII. Distal margin of TIII tridentate; spaces between teeth strongly convex, almost forming additional obtuse teeth (Figs 1, 5). Sternal black spots on SII small and isolated from one another: not touching as in other Mediterranean species.

Ecology. This species was collected exclusively with a Malaise trap placed in the “Riserva Naturale del lago [= Nature Reserve of the lake] Baratz” (40˚ 40’. 6 N – 8˚ 13’.64 E, 30 m), near the sandy shore of the lake (Fig. 11). This Reserve is situated in northwest Sardinia and Lago Baratz is the only natural lake in Sardinia (Martinelli 1998; Borgarello et al. 2000), having formed behind a coastal barrier of wind-formed dunes. The basin is permanent and the area is covered by thick vegetation, whereas the surrounding sandy terrain is favourable to nesting of Hymenoptera. The biotope was surveyed in the years 2001–2005, both through direct collecting and with Malaise traps. Trichrysis baratzsensis was much less common than T. cyanea: respectively 3 and 47 specimens. In 2001–2005 36 species of Chrysididae were found in the Reserve, including all Sardinian endemics and the new species (Strumia, unpublished data). This shows that the Lago Baratz Nature Reserve is a very interesting biotope worthy of the environmental safeguard promoted by the city of Sassari.