H. :\r. Morris 107 



larva bore a pair of brown projections on each segment ot the abdomen 

 which, however, he did not consider to be spiracles, although they are 

 almost certainly the structures which have now been found to be un- 

 doubted spiracles. 



Dufour also considered that the larva had no mandibles, although 

 they are distinctly present. As they are somewhat difficult to separate 

 from the maxillae, this may account for Dnfour's failure to distinguish 

 between the mandibles and the maxillae. 



In previous accounts of larvae of this genus, it is stated that the 

 body is composed of eleven segments. The eleventh segment is described 

 as being large, and divided dorsally into two distinct regions, the 

 anterior region bearing the pair of large spiracles, and the posterior 

 region bearing the posterior processes. 



After a careful examination of this apparent eleventh segment, it 

 appears to me to be distinctly composed of two segments, both regions 

 being actually complete segments. The division between these segments 

 is not very marked dorsally, but there is a slight transverse depression 

 just posterior to the spiracles, which bears a few small setae similar to 

 those borne between the other segments. Ventrally the division between 

 the eleventh and twelfth segments is more clearly marked. 



The posterior processes appear to have a somewhat similar structure 

 to that of the spiracles, and they may be a modified pair of spiracles. 

 It seems more probable, however, that they have been formed by the 

 modification of some structure similar to the protrusible conical struc- 

 tures which are found in the larva of Bibio Johannisdi). In another 

 species of Bibio larva, of which it is hoped to give an account at a later 

 date, these structures are more strongly developed than in B. Johannis. 

 They distinctly suggest that some structures, more or less similar to 

 them, may have developed into the processes of the Scatojjse larva. 



The larva of Scatopse agrees with that of Bibio in possessing twelve 

 trunk segments, in the projecting spiracles, and the fact that the hind- 

 most pair is greatly enlarged and the anterior pair slightly enlarged. 

 This larva further agrees with that of Bibio in the absence of eyes. 



It differs, however, from that of Bibio in the fact that the hindmost 

 pair of spiracles is carried on the eleventh and not the twelfth segment 

 and are much drawn out to form conspicuous elongate processes. Other 

 important differences are seeir in the absence of the characteristic cuti- 

 cular processes so well displayed in Bibio, in the single jointed maxillary 

 palpi, in the pair of fan-like caudal processes to the twelfth segment, and 

 in the pointed and more triangular head. 



