Rileggendo la tua descrizione del Torymidae mi accorgo che manca un'informazione sempre importante ma, in questo caso, fondamentale, per la distinzione fra i due Megastigmus citati sopra.
Le dimensioni dell'esemplare (escluso l'ovopositore).
Ti riporto le descrizioni delle femmine delle due specie, dalle quali appare chiaro come le dimensioni siano determinanti:
Megastigmus dorsalis (Fabricius, 1798)
The female wasp measures 1.9-4.1mm which averages out at 3.2mm excluding the ovipositor.
The head is a rich yellow colour with a sharply defined dark metallic green patch on the vertex. The eyes are large and red/brown, sharply contrasting with the rest of the head and the ocelli are large and dark. The antennae are hairy and yellow brown with dark joints, the scape is dark above and testaceous below. There is one ring and 7 funicular segments which have a taper to the long club.
The thorax has varying amounts of well defined dark metallic green on the top and sides and yellow with traces of brown beneath. The notaulices are deep and full length. The tegulae are straw coloured which lead on to the wings which are clear with mid brown hairs. The veins are mid brown and the stigma is dark with a cloud surrounding it that may vary in size considerably. The legs are all yellow with sometimes brown on the rear coxae. 5 tarsel segments are present and darker claws.
The gaster (abdomen) is a rich brown on the top with points running down the yellow sides and yellow underneath. The ovipositor sheaths are hairy and black and is in length about 3/4 the body length.
Megastigmus stigmatizans (Fabricius, 1798)
The female wasp measures 5.9-6.8mm which averages out at 6.3mm excluding the ovipositor.
The head is a rich yellow colour with a sharply defined metallic red/green patch on the vertex. The eyes are large and bright red, contrasting vivdly with the rest of the head, the ocelli are dark baige. The antennae are dark, short and heavy with one ring and 7 funicular segments with longitudinal hairs on each segment.
The thorax has varying amounts of well defined metallic red shot green on the top and sides contrasting with yellow with traces of brown beneath. The notaulices are deep and full length and there are some hairs present. The tegulae are colourless testaceous which lead on to the wings which are clear. The stigma is shaped like a dark capsule, twice as long as it is broad, with a cloud surrounding it that may vary in size considerably. The legs are all yellow with metallic hairy coxae. 5 tarsel segments are present and dark claws.
The gaster (abdomen) deeply triangular and is a mainly a dull mid yellow with touches of dark brown above. The ovipositor sheaths are long, hairy and dark and is in length at least as long as the body length, with an average of 113% of the body length.
Comunque, anche prima che tu ci indichi le dimensioni, il rapporto fra lunghezza dell'ovopositore e lunghezza del corpo mi sembra indicare chiaramente la maggiore parentela (e penso proprio, a questo punto, l'identità) con M. stigmatizans.
P.S. - Appena avrai risposto, sposterò la discussione sul forum: "Nuove richieste di determinazione..." 
|
)
con, magari, la complicità di Maurizio 