44<S Osten Sacken: on the charactcrs of the three divisions of 



differentiated, not only in thcir shape, but often in tlicir color. I am 

 not aware of sucli a diffcrence between tbe scxes in any genus of 

 Nemocera vera. It occurs again in Simulhnn. 



The chitinous covering of Bibio is tliickei" than that of tlie 

 Nemocera vera and therefore the whole bodj^ is heavier. Thcir 

 V'ings arc broad, and have a heavy arniatnre of veins on the front 

 part only; the posterior veins are weak and generally pellucent, and 

 there is no anibient vein along the posterior margin. They fly well, 

 bnt, as far as I have noticed, they do not direct their motions easily. 



The next relatives of Bibio and Dilophus are Plecia (including 

 Penthetria^ and the genera Spodius and Fachyneura. They all 

 have three well-developed pulvilli, three larga ocelli, and the venation 

 more or less like Bibio, only the veins on the front and bind part 

 of the wings differ less in thickness. The head of the male shows 

 a gradual passage from a long and complete contact of the eyes in 

 several exotic Pleciae and in Penthetria vehitina Loew, from Japan, 

 to closely approximate eyes without actual contact, in the european 

 Penthetria and to a distinct front between the eyes in Spodius and 

 Pachyneura. Bisection, as Observation teaches us, never occurs but 

 with contiguous eyes i) (although contiguous eyes may occur without 

 bisection). As Sjyodius cf and Pachyneura cf have a narrow front, 

 separating the eyes, the latter, in accordance with the above rule, 

 are not bisected. Penthetria holosericea represents a transitional 

 caso: its eyes arc closely approximate, but not in actual contact; 

 nevertheless bisection takes place here. 2) In Plecia the heads of 

 the male are holoptic; bisection occurs in many cases, but not in all. 



It is only recently that I became aware that holoptic male Pleciae 

 occur in two diiferent forms: with bisected, and with unbisected eyes. 

 The european Penthetria holosericea, as well as the Penthetria 

 melanaspis from Java, and its probable synonyms P japonica W., 

 ignicollis Walk, and Crapitnla Motchulskii Gimmerth. have each 

 eye of the male divided by a more or less deep bisecting groove. In 

 the Berlin Museum I saw many male specimens from South-America 



Bibio zu erklären. Die Larve lebt nämlich in der Erde." According 

 to Beling (Verh. Z. B. Ges. 1872, p. 646) the larvae, for the purpose of 

 pupating, descend 7 or 8 centimeters below the surface of the soll, and 

 form a round earthen cavity with smooth walls, in which they remain 

 8—14 days, awaiting transformation. 



1) The only exceptions known to me from this general rule will 

 be mentioned in the paragraph on the Blepharoceridae. 



2) Loew (Wien. Ent, Mon. 1858, p. 103) does not say whether the 

 eyes of the male of bis Penthetria velutina are bisected or not. 



