BY R. J. TILLYARD. 313 



These parallel reductions must be coiiceiYed of as haYing taken 

 place quite apart from one another phyletically, and probably at 

 quite different geological periods. Though passing through the 

 same series of reductions, these three groups arrive at quite 

 different final results, as may be seen by comparing llapliidia 

 (Text-fig.7) with Opcrfh (Text-fig.9) and witli Characiia (Text- 

 fig. 11). 



(5) The highest specialisation of the old jugo-frenate type, still 

 preserYing the original characters of that type, is the jugo-frenate 

 type of the Microjyfprygidcp, in which the jugal lobe is folded 

 under the forewing, so as to become directed forward and out- 

 ward, and the frenulum becomes engaged in the groove so formed. 

 Thus the jugal lobe functions as tlip most archaic form of rctina- 

 cnlnm yet discorcml. 



(6) The origin of the specialised jugum of the HejnalidcE and 

 Protothcoridct is not to be traced dii-ectly from the Micropterygid 

 type, but fi'om an older, unspecialisefl, jugo-frenate type, such as 

 we find in the Planipennia. The jugal lobe remains projecting 

 outwards and downwards, not turned forwards to pass undei' the 

 forewing. At first, it rested upon the ct)sta of the hindwing, as 

 in the older forms of Tiichoptera. The frenulum, being useless, 

 disappeared. A later and higher specialisation led to the length- 

 ening and narrowing of the jugum, and finally to its adopting 

 the position seen in most of the Hej^iaUdce. 



(7) From this, it follows that no existing type within the 

 Lepidoptera of to-day represents the true ancestral form or 

 Archetype of the Ordei\ That Archetype must have possessed 

 an iiiisppcifdiKcd, jayo-frpuatc coapJuai-apparat^is^ probably with- 

 out jugal bristles, as in the Planipennia to-day. The de\elop- 

 ment of the specialised jugo-frenate type of the M icropterycfidix, 

 on the one hand, and of the specialised jayatc type of the Hcpi- 

 alidce and Frotothcoridit on the other, must have pi'oceeded upon 

 diYergent lines. 



(8) The frenate forms amongst the Lepidoptera are also de- 

 rived from the archetypic jugo-frenate foiin, and not directly 

 from the Microptn-yyidce, as is pro^•ed by the bristles of the 

 frenulum maintaininti- their original direction. This line was 



