16 ILLINOIS BIOLOGICAL MONOGRAPHS [258 



wide antacoria, which may be infolded or extended, permitting the antenna 

 to be either protruded for its full length or retracted into the head so that 

 only the distal portion is exposed. The first two segments are large, the 

 third much smaller and the fourth very minute. These are separated by 

 well developed coriae allowing free movement at the joints. The distal 

 end of the second segment bears five primary setae of characteristic form, 

 which may be named by combining Roman and Arabic numerals, the 

 former referring to the segment, the latter to the seta. The seta III is the 

 only one of these with a normal form; II 2 is extremely long and attenuate, 

 being longer than the entire antenna; II 3, II 4, and II 5 are conical, II 4 

 being very minute. The distal end of the small third segment bears three 

 conical setae. III 2 being midway in size between III 1 and III 3. A single 

 attenuate seta is carried by the minute fourth segment. 



Forbes has shown that the first three segments vary in relative size 

 and that the proximal one sometimes bears secondary setae. The figures 

 of Dampf and Tragardh are the only detailed ones of the antennae of 

 caterpillars known to the author. The former investigator directs attention 

 to the difference in the relative size of the conical setae in the Psychidae, 

 where the condition is normal, and in the Talaeporiidae and the tineid 

 Adela degeerella, where these setae are unusually large. Tragardh figures a 

 most interesting series, representing the reduction of the antennae of 

 leaf-miners. The minute size of the distal segment together with the great 

 development of the third and its setae is apparently responsible for his 

 failure to recognize this last segment as such, although it is distinctly 

 shown in his figures. Most of the primary setae named can be identified 

 even in these aberrant antennae. Packard's figures of the larval mouth- 

 parts of Eriocephala appear to show four well developed segments, a unique 

 condition for the order. 



Within the Noctuidae there appears to be no variation in the antennae 

 of taxonomic value, except perhaps the amount of chitinization. This 

 varies from very slight to very heavy, the heavier chitinization being cor- 

 related with a darker color. The habit seems to bear no relation to the 

 amount of chitinization, which varies according to the genus or sometimes 

 within a genus. 



The mandibles of caterpillars have been but little studied, accurate 

 figures of them being scarce in literature. They are joined to the head 

 immediately mesad of the antennae by a narrow mandacoria and to the 

 lateral margin of the maxillae by a wide maxacoria. A large socket, the 

 preartis, on the cephalo-dorsal corner serves for the articulation with the 

 precoila and a large globose condyle, the postartis, on the opposite corner 

 fits into the socket of the postcoila. A small caudal extensotendon and a 

 large cephalic rectotendon provide attachment for the abductor and adduc- 

 tor muscles respectively. The left and right mandibles are usually unlike, 



