ANDRICUS OSTREUS. 77 



antennae unknown to Mayr), the joints from the fifth to the terminal 

 diminishing but slightly in length ; mesonotum and scutellum as with 

 the $ . Wings ciliated. 

 Length 2 mm. 



In this country it is only known from Kew Gardens, 

 where it is found only on Quercus cerris. On the 

 Continent it is found in Austria and France. 



The only other species of Oallirhytis is Andricus 

 Hartigi, Foer., the gall of which has not been described. 



B. Claws bifid. 



1. Keels on median segment bulging outwardly, not 

 straight and 'parallel. 



2. Andricus ostreus. 

 PL VII, fig. 3, gall ; PI. XIII, fig. 9, ? . 



Neuroterus ostreus, Giraud, Yerh. z.-b. Ges. Wien, 1859, 350 ; 



Adler, Zeits. wiss. Zool., xxxv, 199, pi. x, 



fig. 19; Lichten. Oyn., 64, pi. x, fig. 19; 



Mayr, Eichengallen, 47, pi. vi, fig. 67; 



Schenck, Nass. Oyn., 68, 72, and 105. 

 Andricus ostreus, Mayr, Eur. Cyn., 14. 



Dark brownish-black, the head and thorax streaked occasionally with 

 dark rufous ; the legs rufous-yellow, the base brownish ; sometimes the 

 rufous tinge is absent. Antenna? longish, thin, very slightly and 

 gradually thickened towards the apex. Head and mesonotum finely 

 shagreened ; the scutellum rugose. Wings longish, very slightly 

 fulvous tinted, the apex with longish cilia?. Thorax finely pilose, more 

 thickly on the scutellum, shining ; abdomen shining, glabrous. Ventral 

 sheath triangular, much longer than broad. 



Length 2 — 2^ mm. 



Gall. — Found in August and September on (as a 

 rule) the midrib on the under side of the leaf ; and at 

 the base is situated between two brownish membranes 

 as long, or even longer than, the length of the gall. 

 The gall is from 1 to 2 mm. in length, roundish or 

 ovoid or oval; whitish or greenish with pink spots 

 when young, becoming whitish-yellow when old ; 

 smooth, shining, and bare. Often the pink or red- 



