1919.] 95 



(fig. 2, B). There is no posterior caecum connected with the mid- or 

 hind-gut. 



In the larva of Bib/'o joliannis L., a good description of which we 

 owe to Morris (1917), the four Malpighian tubes also arise from a 

 common duct, but this joins the left side of the alimentary tube. 

 Besides the three anterior caeca, this larva shows a posterior caecum 

 which originates from the venti'al side of the posterior end of the 

 mid-gut, the caecum being directed forward. The alimentary canal of 

 the larva of Dilophus vulgaris Meig., described by de Meijere (1915, 

 p. 185), and D. fehrilis L. (fig. 2, C) is similar to that of B. jo- 

 liannis L., as described by Morris, except that the Malpighian tubes 

 in Dilophus arise fram the dorsal side of the alimentary tube. 



Anterior lateral caeca of similar structure to those in the Scatopse 

 larvae also exist in all the larvae of the Mycetophilidae and Ditomyidae 

 {Ditomyia and Symmerus), but the two posterior lateral caeca of Sea- 

 topsidae have not hitherto been observed in other Dipterous larvae. 

 The single posterior caecum, as seen in Bibionid larvae, was found by 

 Dufour (quoted by Morris) in the larva of Tipida lunata L., and by 

 Anthon (1908) in that of Ctenophora aiiyusfipeiinis Lw. In a Tipulid 

 larva, boring in a dead branch of elm, I found a posterior caecum of a 

 very large size. In other Tipulid larvae (for example that of -E^?- 

 phrayma oceUaris L. ) this caecum is very much reduced. It is possible 

 that the study of other Bibionid larvae will supply the link between the 

 forms with a very well-developed posterior caecum and those which, like 

 Bihio hortulanus, do not possess a trace of this organ. 



Very few parasites have been recorded on the larvae of Bibio. 

 Lyonet (1832) has recorded a mite and a nematode which he found on 

 a Bibio larva, but he states that he was unable to say whether they were 

 true parasites.* 



Malloch (1917, p. 300), who reared a Hymenopteron from one of 

 his breeding-cages containing Bibio larvae, doubted its parasitic relation 

 to Bibio. Morris states that he never met a parasite of Bibio joliannis 

 L., and he quotes only the previous observations of Lyonet and those of 

 Malloch. 



* The following is a passage containing his observations :—" J 'ai trouve sur ce ver deux sortes 

 d'insectes. Je ne puis dire s'ils sont parasites, ou si le hasard les y a fait rencontrer. Le premier 

 avoit environ une ligne de longueur. II etoit blanc, plat et extrcmenient minte. C'e'toit une espfeee de 

 Taenia sans articulation. L'un de ses bouts me parut romiiu. II se donna beauooup de mouvements 

 mais sans avancer ni reeulcr. La fig. 14 en fait voir la forme ties en grand, et la fig. 3 trace assez 

 grosaierement celle de I'autre insecte, que je ne pus bien repre'sienter, parce qu'il m'echappa lorsque 

 je commenijai a en deasiner les contours. II etait plus petit qu'une mite, avait huit jambes, et 

 I'extremite de son corps etoit fouichue, dans le s^Mig que la figure le fait voir." I)e Haan, who 

 edited Lyonet's work and who was responsible for the explanations of his figures, deserves credit for 

 recognising Lyonet's " Taenia without articulation " as a Nematode. On the other hand, it is diffi- 

 cult 10 understand his explanation of Lyonet's fig. 3 (p. o. vii) as a " louse found on the larvae," for 

 the figure itself, as well as Lyonet's test, clearly shows that it is a mite. 



