8 Orthorrhapha brachycera. 



the copulatioii. Loew on the other hånd declares (Mon. of Dipt. of 

 North. Am. II, 1864, 5) that they: "must be considered as organs of 

 great irritability, as the roots of the hairs on their inside are con- 

 nected with nerves." — The hypopygium is either exposed and 

 pedunculated, the seventh segment forming the peduncle, and it is 

 then bent in under abdomen and laid more or less up in the groove 

 formed here; or it is more or less imbedded at the end of the abdomen, 

 and then only partly or almost not at all visible; also in the latter 

 case it is bent in under the abdomen, with the posterior end pointing 

 more or less forwards, and the ventral side turned upwards. The 

 described appendages are often not all to be seen without dissection, 

 especially when the hypopygium is imbedded, and sometimes they 

 are not at all visible, or only the outer lamellæ. ^ In the female the ab- 

 domen has generally five visible segments, the three foUowing hidden, 

 but sometimes more than five to all eight segments are seen; it 

 terminates with a small ovipositor, which generally has some small 

 spines above, and a pair of styles or small lamellæ below; in some 

 cases the spines are wanting. Sometimes the ovipositor is larger 

 and knife-shaped (e. g. Thrypticus). Dot-like impressions at the side 

 margins of some of the abdominal segments (such as also sometimes 

 found in other families) are always or nearly always present and 

 generally rather conspicuous; they are most often found on the 

 second to fourth segment, sometimes on more, and they may also, 

 but rarely, be present on the flrst; they seem in some cases only to 

 be present in the female. The abdominal segments have generally 

 hindmarginal bristles, which are longest on the first segment; some- 

 times they are small and indistinct, except on the first segment, and 



' According to Snodgrass 1. c. and to the above description, the hypopygium thus 

 in general has the following appendages: ventral lobes, one or two pairs (not 

 articulated); two pairs of inner lamellæ (after Snodgrass sometimes three pairs, 

 [Pelastoneurus laetus]), one pair of outer lamellæ, and an unpaired dorsal median 

 appendage (articulated). The distinction between ventral lobes and lamellæ is 

 generally not drawn in earlier descriptions; thus Kowarz says in his paper on 

 Medeterus (Verhandl. Zool. bot. Geseli. Wien, XXVII, 1877, 42, note 1): "Das 

 Hypopygium hat bekanntlich vier Paare Analanhånge", and Schiner says (F. A. 

 I, 203) about Tachytrechus, that the inner appendages are more numerous than 

 in the following genera. In both cases both lamellæ and ventral lobes are 

 considered. — A thorough study of the male genitaha of the Dolichopodids 

 might perhaps make it possible to compare them with the genitalia in other 

 families as f. inst. the Empidids; it is perhaps not impossible that the outer 

 lamellæ in the former might answer to the outer or lower lamellæ in the latter, and 

 likewise the two pairs of inner lamellæ to the upper or inner lamellæ in the 

 Empidids, which are often two-branched (as they are also in the Asihds). 



