264 Orthorrhapha brachycera. 



pair of lamellæ inwards; the genitalia are somewhat different in the 

 various species. In the female tlie abdomen is pointed, and the eighth 

 segment terminates with two thin styles. The legs are long and slen- 

 der, the hind legs longest, the front legs the shortest; the front coxæ 

 a little elongated; the front femora are thickened in both sexes, also 

 the middle femora are a httle thickened; sometimes also the front 

 tibiæ are somewhat thickened, and then most in the male; the tarsi 

 are long. Front and middle femora have two rows of very short 

 spines below, between which the tibiæ can be laid up. For the rest 

 the legs are short-haired and with very few bristles. Tibiæ without, or 

 the anterior tibiæ with very small apical spurs. There are two claws, 

 two pulvilli and a small, linear empodium with bristles below. Wings 



Fig. 121. Wing of T. nubila. 



with the mediastinal vein short and weak, not reaching the margin; 

 the cubital vein unforked and thus one cubital cell; the discai vein 

 likewise miforked and thus three posterior cells; no discai cell; the 

 lower branch of the postical vein present and somewhat recurrent, 

 but no anal vein or anal cell is present; the basal cells long, the se- 

 cond a little longer than the first. No stigma. The axillary lobe 

 somewhat developed, the axillary angle very shallow. No alula, the 

 margin here a little fringed. Alar squamula very small, fringed at the 

 margin. 



The developmental stages are not known. Boie mentions (Stett. 

 Ent. Zeitg. VIII, 1847, 331), that he has bred a Tachydromia from 

 flowers of Bidens cernuus; the species might belong to the pre- 

 sent or the following genus, but there is no doubt some mistake 

 here. 



The species of this genus are rather characteristic by their 

 elongated shape, and also by their behaviour; they occur especially 

 on the stems of trees and on boards, and they are here seen run- 

 ning swiftly about with the wings parallel over abdomen, but they 

 fly rarely. I have never taken them with prey, but they are known 

 to be raptorial, as is also indicated by the shape of the anterior legs. 

 Poulton records in the work cited above T. nuhila with Cecidomyia sp. 

 as prey. 



