I08 B.C. EXTOMOLOGICAL SOCIETY. 



" 6. Larval Tubercles. — The arrangement of the tubercles is remark- 

 able from the fact that, more than any other larval structure, they have 

 undergone modification for protective purposes. In concealed-feeding 

 larvfe the tubercles have usually remained simple, the setae often being 

 suppressed until they form mere points on the chitinous button of the 

 tubercle. On the other hand, in exposed-feeding larvae they vary from 

 entire absence (where their presence would interfere with the protective 

 coloration adopted by the lar\-?e) to raised warts bearing many- setse ; 

 or they may form a prolonged spiny base bearing several setiferoiis 

 branches; or develop fascicles of urticating spines; or hairs may 

 arise from the normal base. In spite of this, however, two characters 

 remain fairly constant: ( i.) Tubercles I. and II. tend to form (by union 

 or by the atrophy of I. or II.) a single sub-dorsal wart, or, on the other 

 hand, tend to become arranged as anterior and posterior trapezoidals. 

 (2.) Tubercles IV. and V. both remain as sub-spiracular tubercles, or, 

 on the other hand, V. remains as a sub-spiracular and IV. becomes a 

 post-spiracular tubercle. We do not think the pre-spiracular tubercle 

 (which is more or less adventitious) of much value in classification, but 

 the two above characters appear to be so. 



" Now, it is evident from the above brief summary that the structure 

 of the larval prolegs, the characters offered by the movable pupal seg- 

 ments, the broad characters of neuratioh, and of the jugum, only help us 

 to separate, as it were, the generalized from the more specialized super- 

 families. These characters still leave them unsorted, and give us no 

 clue to their relationship to each other. 



" It is quite evident that the evolution of the many specialized super- 

 families has taken place from the generalized, and that the former are 

 the most recent evolutionary products of certain stems of which the 

 generalized are the older offshoots. What is needed, then, is some 

 character or characters that will not slice off horizontally, as it were, 

 all the branches of the genealogical tree, leaving (i) the upper super- 

 families, composed of the Obtectae or specialized Frenatae, and (2) the 

 lower, comprising the Incompletae or generalized Frenatae, but one which 

 will give us clues as to the development of the branches themselves 

 vertically, and separate into their own particular branch the specialized 

 and generalized superfamilies belonging thereto. In this way alone can 

 we get a true conception of the genealogical relationship of the various 

 families to each other." 



Mr. Tutt then goes on to show how the groups work out according 

 to Dr. Dyar's studies of the larval tubercles, but considers that the 

 arrangement leaves us much as we were. He then continues : — 



" There was sufficient material here for the basis on which to 

 construct the broad lines of a natural genealogical tree, if used in con- 

 junction with the tables given us by Chapman and Hampson. But 

 the desiderated clue as to the actual details of such was not obtained 

 until the publication of Chapman's valuable paper, ' The Phylogeny and 



