35] LEPIDOPTEROUS LARVAE— FR ACKER 35 



of the spiracle. The fact that kappa is usually much lower down, and is 

 often associated with eta, indicates the error of a view which would call 

 this seta theta. This is further emphasized by the subprimary nature of 

 theta and by the fact that eta and kappa already have homologies on 

 Hepialus without the use of theta. Forbes' (1910) error on this point 

 was rather far reaching so far as homotypy is concerned. He gives only 

 four figures, but in the setae epsilon, theta, kappa, eta, and mu, there 

 are four eases* in which the same label is given in one place to a primary 

 and in another to a subprimary seta. Most of these associations would 

 be very difficult to explain and they are wholly unnecessary. The mis- 

 takes are due, not to errors in observation, but to a failure to take the 

 primitive first stage into account. 



Kappa. This is a fundamental, ancestral, primary seta and is read- 

 ily transformed into a scolus or verruca. It occupies a position about 

 the level of the spiracle and is almost never absent. In forming ver- 

 rucae it is often associated with theta and eta, and on the prothorax of 

 most of the Microlepidoptera a chitinized pinaculum bears all three. In 

 specialized Microlepidoptera kappa and eta are always adjacent on the 

 abdomen, where they take all possible positions with respect to each 

 other. In most cases the dorsal of the two is called kappa. 



On segment 9 kappa is obsolete in certain Pyralididae. The begin- 

 ning of the reduction is shown in Phycitiuae (Fig. 46) where eta is 

 located on the same pinaculum with kappa and mu but is much larger 

 than the other two. In Pyraustinae (Fig. 49) only eta remains. This 

 condition is not sufficient, however, to justify us in calling the sole 

 representative of the Kappa group on the ninth abdominal segment of 

 Noctuidae, "eta", for here the position on the newly hatched larva, 

 especially in its relation to rho and pi, shows that it is the caudal rather 

 than the cephalic seta of the group which has been retained. (See Fig. 

 30.) 



Eta. On the meso- and metathoracic segments of the Frenatae, eta, 

 like theta, appears at the first molt. It is below kappa and is often asso- 

 ciated with it. On Hepialus it is wanting on the mesothorax and meta- 

 thorax but present on the prothorax. At the time of the separation of the 

 Jugatae from the Frenatae it had appeared only on the prothorax and 

 abdomen or had been lost on the other thoracic segments. In the latter 

 place it has since become established in the Frenatae after the first 

 instar. 



This is one of two cases where it has seemed necessary to consider 



♦These are: iii (primary in all except Fig. 4) ; iv (primary on Figs. 4, 5, and 

 34, subprimary on Fig. 33) ; v (primary on Figs. 5, 33. and 34, subprimary on Fig. 

 4) ; vi (primary on Fig. 33, subprimary on Figs. 5 and 34). 



