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The description is made from two fresli maie spécimens, taken 

 by Mr. Bykow in the year 1893 at the village Kasakévitcheva 

 on the river Ussuri near the city of Khabarovsk (Amoorland). 

 Female unknown. The spécimens are now preserved in the col- 

 lection of the Kussian Entomological Society in St. Petersbui-g. 



I name this species in the honour of my esteemed friend Mr. 

 H. Blöcker, eminent lepidopterist of St. Petersburg. 



Biston hypoleucos, n. sp. 



(Fig. 1-2). 



Expanse of maie 44 and 48 millim. 



Antennae of maie whitish-gray, bipectinated for tlii*ee-foiu'ths 

 length, with stiff branches. Palpi very small, hairy, brownish- 

 gray. Proboscis weak. Frons hairy, brownish-gray. Vertex hairy, 

 white. CoUar and thorax grayish- white. Middle of collar spotted 

 with brown. Abdomen grayish- white, indistinctly ringed with 

 pale-brown; щзрег part of the Ist and 2nd somites spotted with 

 gray. Underside of thorax gray. Tibiae and tarsi whitish, ringed 

 with gray; the Ist pair of spurs of liind tibiae are near the 

 extremity. Abdomen on the underside white, without rings. 



Wings not crenulated, formed completely as in Bist on betula- 

 rius Linné. 



Ground-colour pale grayish-white ; fine dark points and 

 streaks, characteristic of the genus, completely absent; but the 

 whole space of wings is covered with isolated dark scales. 



Transversal lines of fore wing black, very fine in one spéci- 

 men, almost absent, and visible only on the veins, in the other. 

 Antemedial line of fore wing slightly angled at median and at 

 dorsal veins ; inwards it runs a broad brownish band, separated 

 from it by a white one. Medial line visible, but indistinct, paral- 

 lel to postmedial line; discocellular spot clear. Costa without any 

 spots. Postmedial line angled outwards at vein 5 and excurved 

 between veins 1 and 2 (in one spécimen), or represented only 



