227 



1910.] 



"Inrnsticella they are larger and more robust. The several dimensions 

 are as follows :- b^sticella. weaverella. 



,, „ n-U mm 0'32 mm. 



Length of imcus u cs-i mm 



^, ,, clasps 0''^! " " 



A.OQ 0'65 „ 



„ saccvis '^ '^'^ " 



Width of clasps 0-27 „ O'^G » 



Length of dorsal hooks 0'33 „ 0'30 „ 



" The form of the clasps is different, so that the widest part in rusticdla is 

 0-3 mm from the extremity, whilst in weaverella it is nearly 0'4 mm., so that 

 the clasps look round and broad in rusticella, narrow and tapering in weaverella. 

 The hairs along their upper outer margins extend much further back m 

 weaverella, and have the appearance of being each on a little eminence, which 

 one misses in rusticella. The dorsal hooks are stronger and more curved m 

 rusticella. No doubt the most striking difference is in the length and strength 

 of the saccus, as noted above in dimensions. The aBdceagus seems to be longer 

 and more robust in rusticella, but the specimens I have mounted unfortunately 

 obscure this organ somewhat in weaverella. 



" I have examined a few other of these rubbish-eating Tmsce, and 

 find they all have male appendages of a common pattern, but with 

 much variation in proportions of parts. The point of greatest interest 

 in connection with M. rusticella is that T. pallescentella, which diiters 

 so much from M. rusticella in its neuration, has appendages that differ 

 from those of M. rusticdla and weaverella hardly more than they do 

 from each other." 



Comparison of female genitalia of M. rusticdla and weaverella. 

 "The photographs of the two species show the female organs to be very 

 much alike ; the rods are of identical length, and the small terminal plates of 

 the ovipositor apparently so also. Unfortunately the dorsal and ventral plates 

 of the seventh abdominal segment were left in the preparation of weaverella, 

 and as a resvdt, the hursa became ruptured. The vaginal tube appears to be 

 shorter in weavereUa than in rusticella. The photograph (and preparation) of 

 rusticella is a fairly satisfactory one, showing the bursa and attendant sac. 



"In both species there is a line of small chitinous plates forming a zone 

 round the middle of the hursa ; these seem very much the same in both insects, 

 and fourteen in niunber in both cases, though the bursa being ruptured m that 

 of weaverella may perhaps permit doubts as to this being accurate. On the 

 other hand, when the bursa remains intact, these little plates, which are com- 

 plicated in form, and seem to have a point free from the bursal wall, lie over 

 one another (from opposite sides and at margin) so as to make counkng them 

 somewhat difficult, especially as, in rusticella, some specimens have ourteen 

 and some sixteen plates. That photographed has sixteen. These little plates 

 seem to be attached to the wall of the bursa by one margin, the pate itself 

 swino-in. free in the sac. The lines of attachment are parallel with the length 



