154 AN A ceo UNT OF BRITISH FL IBS. 



segment somewhat smaller and having two black dots upon its dorsal 

 surface. Several tubercles surround the base of anal segment. 

 There are also two lateral tubercles on each segment, and two rows 

 of four each on the ventral surface. They may be found in May 

 and June under wet moss ; they turn to pupae during the latter end 

 of June. 



In Scatopse the larvae are fusciform, legless, as in the others, witli 

 r^vo short points on the thorax at the side, and also on the eight 

 abdominal segments at the base : the last segment is terminated by 

 I wo divergent setEe. 



The pi(p(z are naked, enclosed in an oval cell ; thorax gibbose, 

 markings of wings and legs very short, usually pale in colour {Di/o- 

 Z'/ii/s). 



Th& pupa of Bibio (Fig, 2, PI. iii.) is dark brown, and has a curious 

 shrivelled appearance, about one-third. of an inch long and very broad. 

 The anal segment is very small, and has two divergent spines on its 

 dorsal surface. The wing cases are small and closely surround the 

 legs. The thoracic portion is much elevated. The flies hatch during 

 July. I have to thank Mr. Bignell for the loan of the specimens 

 figured. 



Their range in space is wide: they occur abundantly from Scandi- 

 navia to the tropics, and in America they appear in great numbers, 

 and do considerable damage to crops. Their geological range 

 is limited, but no insects occur so abundantly in a fossil con- 

 dition as the Bilnoiitdce* They appear first in the tertiary beds ; 

 there are records of their appearance in the mesozoic, but the species 

 are very doubtful, and we cannot place the true record of their 

 appearance further back than the tertiary period. But in the tertiary 

 epoch they are the most abundant insects ; they are not, however, 

 ri. h in species, but what do occur are found in great numbers. They 

 are rare in amber. Loew found the genera Dilophus, Plecia and 

 Scatopse ; Bibio is strangely enough wanting. Plecia also occurs 

 abundantly in the rock formations in Aix, Oenigen, Auvergne, Wyom- 

 ing, etc. Bibio occurs most abundantly in the rocks, between forty and 

 fifty species have been described from various places in Europe and 

 America. There seem to be some extinct genera found, such as 

 Epiplecia, Siard, which occurs at Covent ; also Protomyia and Bibi- 

 opsis, genera formed by Heer, but which are considered by Loew not 



* Note sur les Bibionides fossilis. Bull. Sc. dep. Nord. T. i., Lille, 187S ; also 

 Bit)ioniden aus der rheinischen Braunkohle Von. Rott. Pal. Band. .Siard. xiv. Taf. 

 8 and 9, 1865. Heyden, etc. 



