CIRCUMFILI OF THE CECIDOMYIIDAEi 



These peculiar antennal structures are v/hat have been more 

 generally known as arched filaments. They were first discov- 

 ered by Targioni-Tozetti in 1888 and independently observed 

 by Kieffer in 1895. They are most highly developed in the male 

 Diplosids [fig. 43], consisting in these forms of nearly homogeneous 

 whorls of long, looped filaments extending around the en- 

 largements of the segments. Each loop is closely fused to the 

 base of its fellow, and the entire whorl presents every appear- 

 ance of being one structure. This peculiar development also 

 occurs in female Diplosids, being represented in this sex by 

 slightly elevated, nearly colorless threads supported by minute 

 stalks. There is usually, in this sex, a circumfilum near the 

 base and one near the apex of the enlargement of each segment, 

 the two being connected by one or more longitudinal fili. There 

 is very rarely a connection between the two or three circumfili 

 on a segment in the male Diplosid, though an evidently abnor- 

 mal connection of this character has been observed in the case 

 of the male Hormomyia americana Felt [fig. 42] . The 

 homologous character of these apparently different structures in 

 the two sexes is confirmed by the fact that in the male Bremia 

 [fig. 44] the basal circumfilum of the distal enlargement is low 

 and exactly like that of the female. These structures occur not 

 only in the Diplosids but also in practically all other Ceci- 

 domyiinae, not being present, so far as known to us, in the 

 Lestreminae. The genus Lasioptera has these structures in a 

 very simple form, they being in both sexes merely sHghtly ele- 

 vated threads supported by slender stalks and joined on at 

 least one face of the segment. Rhabdophaga and its allies have 

 a similar arrangement, except that in the male there is a slight 

 indication of greater specialization, and the same is practically 

 true of Rhopalomyia. The most striking variations on some 

 accounts are those found in the Asphondyliariae. The circum- 

 fiH in the male Asphondylia [fig. 38] consists of a more or less 

 variable series of extremely tortuous, slightly elevated threads 



* Read at the third meeting of the Entomological Society of America held 

 at Chicago, III, December 30, 31* ^907- 



