ANDRTOUS EADIOTS. 85 



cated. Head and thorax strongly acicnlate, the 

 scntellum distinctly rugulose ; head and thorax with 

 the pubescence thick and longish; the dilatation behind 

 the eyes distinct ( = A. trilineatus). 



Small Form (1 — 1\ mm.). — Head and thorax black 

 or fuscous-black ; the sutures of the mesonotum 

 sometimes yellowish-red ; the abdomen reddish-yellow, 

 blackened at the apex above; the legs pale yellow- 

 red ; the base of the coxse blackish ; antennae yellow- 

 ish-red at the base, the rest fuscous; punctation on 

 head and thorax very fine, sometimes obsolete; the 

 dilatation behind eyes indistinctly developed. 



Between the two extremes there are numerous 

 intermediate variations. 



Gall. — Found in twigs, or more rarely on the 

 petioles of the leaves, usually gregariously. They are 

 oval or ovoid, about 2 mm. in length, embedded in the 

 wood or in the bark, or partly in both. The galls 

 have no very distinctly lined membrane. When they 

 occur in numbers, the petiole, more particularly on 

 twigs, becomes irregularly distorted, with raised points 

 where the galls are. When the insects escape they 

 leave a round exit hole by means of which the presence 

 of the galls is easily noticed. The flies escape early 

 in the autumn. 



The sexual has fewer parasites and inquilines 

 than the larger agamic form. They are Ceroptres 

 arator, Sajoholytus connatus, Htg. ; and Synergus 

 apicalis, and according to Kaltenbach, Synergus vul- 

 garis. The parasites are Megastigmus dorsalis and 

 Pteromalus quercinus, Gir. (Giraud). Very widely 

 distributed in Britain. 



Continental distribution : Sweden, Switzerland, 

 Germany, Austria, France. 



