DIPTERA 51 



fourth vein nearly straight, fifth straight as far as the posterior transverse vein and then 

 curved suddenly downwards to the posterior margin of the wing, sixth rudimentary ; 

 between the third and fourth longitudinal veins two transverse veins are present, one 

 opposite or a little beyond the termination of the first longitudinal vein, the other 

 opposite or a little beyond the posterior transverse vein, the two last sections of the 

 fourth vein as thus divided about equal in length, discal cell united with the posterior 

 basal cell, anal cell present but inconspicuous. 



Tj'pe of genus : /. pcrkiiisi, sp. nov. 



As only one male of this genus is represented in the collection (that of the typical 

 species) it is impossible to say yet whether certain characters, such as the strong curva- 

 ture of the costa and the tuft of hairs on the fore tibiae are of specific or only sexual 

 value, but I rather suspect the latter to be the case. 



Key to species. 



1. Scutellum dark with yellow median stripe 2. 



„ entirely dark on dorsum, with bright yellow margin {4) I. pida. 



2. Face, antennae, and palpi black 3- 



Face yellowish, antennae with basal joints obscurely yellow, palpi yellow (j) /. oahuensis. 



3. Metanotum with yellow median stripe, femora with onlv the bases and tips 



infuscated {i) I- perkinsi. 



Metanotum entirely black, femora blackish with tips yellowish {2) I. obsciiripes. 



(i) Idio7)iyia perkinsi, sp. nov. 



Z- Long. Corp. 7 mm.; al. 8 mm. Front reddish-yellow with a transverse brown 

 band behind the antennae, orbits as far as the most anterior fronto-orbital bristle and the 

 vertical triangle black, face, proboscis, palpi and antennae black, the second joint of the 

 latter with a tuft of stiff, black hairs, arista with long hairs along the whole length above 

 and the apical half below, also with a very short thick pubescence between the long 

 hairs. Thorax with the greater part of the dorsum blackish, anterior edge yellow with 

 two median longitudinal black lines, humeri and lateral edges yellow, pleurae yellow with 

 a shining black patch above the front coxae and a smaller one beneath the root of the 

 wings, scutellum and metanotum black with yellow median stripe, halteres light yellow. 

 Abdomen blackish-brown, shining, with obscure yellow markings at the anterior angles 

 of each segment, the whole of the dorsum covered with fine bristles which are some- 

 what longer near the hind margin of each segment. Legs reddish-yellow, the apices 

 and bases of all the femora and the two hinder pairs of tibiae slightly infuscated, 

 fore femora with a few bristles on the outer side, fore tibiae with a conspicuous tuft 

 of hairs at the base, intermediate tibiae with a strong subapical and a single apical 

 bristle, hind tibiae with only a rather weak subapical bristle. Wings slightly tinged 

 with yellowish-brown, the apex broadly infuscated, leaving a very narrow margin 



7—2 



