﻿AUSTRALASIAN STILT-LEGGED FLIES — STEYSKAL 177 



Crosa is dedicated to that master dipterologist, Carl Robert von 

 Osten-Sacken, and the name is formed from the initial letters of his 

 name. 



16. CROSA SEMILAUTA (Osten-Sacken), new combination 



Figure 74, c, d 



Eurybata semilauta Ostkn-Sacken, Berliner Ent. Zeitschr., vol. 2t>, p. 207, 

 1882.— Fkey, Not. Ent., vol. 7, p. 7G, 1927.— Henniq, Konowia, vol. 14, p. 302, 

 1935. 



Philjppixe Islands : Luzon ( Los Banos; Mount Maquiling) ; Min- 

 danao (Zamboanga) ; Tayabas (Lucban) ; Samar (Osmena). 



Previously recorded from localities in Luzon, Mindanao, and 

 Samar. 



17. CROSA TETRAS (Steyskal). new combination 



Eurybata tetras Steyskal, Occas. Pap. Mus. Zool. Univ. Michigan, No. 502, p. 2, 

 1947. 



The type material, from the Solomon Islands, is evidently con- 

 generic with C. semilauta. 



18. CROSA YAPENSIS, new species 

 FIGURE 74, i 



Male. — ^Length of body, 6.5 mm. ; length of wings, 4.5 mm. Color 

 yellow, except extreme tip of femora and tibiae, dorsum of abdomen 

 and anterior part of parafrontal stripes, which parts are brown. 

 There is a faint preapical band of brown on fore femora and the 

 apical tarsal joints are a little darkened. Mesofrons golden brown, 

 becoming blackish in ocellar region. 



The entire insect is shining or subshining except mesofrons, frontal 

 orbits anterior to parafrontal stripes, antennae, and a heavily tomen- 

 tose pleural stripe. Anterior frontal orbits narrowly golden tomen- 

 tose. Pleural stripe bright white when viewed very obliquely, but 

 otherwise dull lead colored; it covers the narrow lower margin of 

 propleura and continues across mesopleura as a stripe as wide as fore 

 tibiae. The stripe, were it to continue across the sternopleura, would 

 run into the uppermost two posterior sternopleural setae. Para- 

 frontal stripes with a bluish reflection. 



Head very similar to that of C. semilauta (fig. 74, c, d), but aristal 

 hairs only half as long as in that species. 



Wings clear hyaline with brownish-yellow veins. Third and fourth 

 veins converge to within a distance equal to length of ta. Pterostigma 

 obsolete. 



