ANTENNAE OF LEPIDOPTKUA. 47 



extreme forms as Satnia cecropla ami EuvdHexm antiopa, but that 

 each is best adapted to the other structures and to the life habits of 

 the possessoi", and is most efficient in supplyin^j the needs of its ex- 

 istence, is perhaps un(|uesti()ned. Samia cecrojna is chiefly nocturnal ; 

 even in closely allied diurnal forms, such as Callosaviia promdhea, 

 vision a})pears to be of little service as a j^uide to the motion of the 

 moth ; and in such forms \\c find a higher degree of development 

 in pectinations which bear an abundance of long sense-hairs of the 

 third type. Eiivanessa and the skippers and butterflies in general 

 ajDpear to have excellent vision, and in no case do they have pecti- 

 nations or sense-hairs of the third type. The pits and rods, how- 

 ever, which are common to all families of the LejDidoptera, reach a 

 higher developnient in Euvanessa than in Samia. We may assert, 

 then, with a fair degree of confidence that the antennae of the but- 

 terflies are more limited in their functions, but that within the limits 

 of their scope they are more efficient. 



SUMMARY. 



The character of the subject of this thesis makes it difficult to 

 sunnnarize the results of th(^ work. The niore important features, 

 however, may be noticed under the following numbers: 



1. jNIuscles in the head move the scape ; muscles in the scape move 

 the pedicel ; distad of the scape no muscles have been demonstrated, 

 and the clavola is therefore capable of motion in itself only when 

 acted upon by some external force causing a flexure and a subsequent 

 extension. 



2. Besides organs for protection, there are at least six types of 

 sense organs situated in the antennae, and all but one are developed 

 from a simple sense-hair inserted at the ectal end of a pore-canal 

 through which it is connected with a multinuclear sense-cell. 



3. The antennae doubtless function as sense organs of touch, smell 

 and hearing, altliough those senses are not subject to the same limi- 

 tations as in the higher animals and may be considerably diflerent 

 in their range of perception. ' 



4. T!ie antenme show that all Lepidoptera are descended from 

 one primitive stem form, of which we may preilicate the more essen- 

 tial features of structure. 



5. The evohition of ventral expansions, of pectinations, of the 

 chitinous surface, of the sense organs shows an increasing differen-- 

 tiation of structure following the demand for increasing specialization 

 of function. 



TRANS. AM. ENT. SOC. XXIII. MAECH. 1896. 



