446 Osten Sacken: on the characters of the iliree divisions of 



„contains no brain", althougli, according to Brauer, they belong to 

 bis eucephalous larvae. 



2. Nöinocera aiioiiiala. 



Tbe group of Nemocera anomala, as I bave already cxplained 

 in tbe introductovy cliapter, is an artificial one, intended to receive 

 for convenience's sake, tbose fornis of Diptera witb filiform antennae 

 and filiform palpi which, on account of tlieir aberrant characters, 

 cannot be included witbin tbe bomogeneous group of tbe true Ne- 

 mocera. The principal aberrant characters of such forms, as we 

 know them at present, consist: 1) In tbe frequent occurrence of ho- 

 loptic beads in the male sex; 2) in tbe absence of the so-called 

 „sensitive hairs" on the antennae; 3) in the occasional presence of 

 well-developed pulvilli; 4) in tbe presence of three distinct, rather 

 large ocelli in the three principal families of tbis group : the Bibio- 

 nidae, Blephnroceridae and Rhyphidae, while aniong tbe Nemocera 

 Vera ocelli occur in tbe family Mycetophilidae and in the Lestre- 

 mina only; 5) in the abnormal character of the larvae. 



All the five families now composing the group of Nemocera 

 anomala contain a majority of forms with boloptic heads in tbe male 

 sex. Exceptional cases, where tbe males are dichoptic, occur among 

 tbe Blepliaroceridae (Liponeura, Paltostoma, Apistomyia), tbe 

 Bibionidae (narrow front Spodius cf, Pachyneura cf) and the 

 BhypMclae (narrow fronts in Lobogaster d" and Olbiogaster cf)\ 

 the close relationship bowever of tbese dichoptic genera to the bo- 

 loptic ones, which are in tbe majority, cannot be contested. 



It is possible, and even probable, that new forms will be disco- 

 vered, aberrant from the Nemocera vera in yet other ways than 

 tbose already known. It will be then found convenient to place them 

 among the Nemocera anomala. The experience we had with the 

 artificial group of Lhnnobina anomala has proved tbe usefulness 

 of such temporary arrangements. 



I bave already spoken (p. 425) of the interest connected with tbe 

 Nemocera anomala as representing tbe remains of long-extinct faunas 

 and of past entomological horizons. 



Bibionidae. The bulk of tbis family consists of tbe genera 

 Bibio and Dilophus which in their structure offer a strong contrast 

 to tbe Nemocera vera. The males bave a boloptic head with a long 

 line of contact of tbe eyes between the antennae (placed very low) 

 and tbe ocelli; the lower part of the eyes in the male is cut off by 

 a deep groove, at the bottom of which tbe facets are more or less 



