July i8i/..] 



PSYCHE. 



3'J7 



the spiny areas in two species. Trcmcx 

 coliimba (Linn.)< antl Ufoccnis cres- 

 soiii Norton, both ot" which have them 

 very well developed l)oth on the wings 

 and thorax. The patch on the wings 

 bears a close resemblance to that of the 

 Heterocera except that the spines are 

 more blunt. The patch on the thorax 

 can be seen with the naked eve. See 

 Fig. I r, s, and Fig. i 2. 



The question at once arises for what 

 use are these organs.'' The theory of 

 Donitz that tliey are for sexual attrac- 

 tion seems hardly tenable. In this case 

 the}' must necessarily ]5roduce a sound, 

 for thev could attract in no other way. 

 This seems scarcelv possible, however, 

 when we consider the relative tlirections 

 in which the spines of the two areas 

 • point when they are in contact. In all 

 cases the spines of the two areas point 

 in opposite, or nearly opposite direc- 

 tions, and an attempt to rasp one surface 

 over the other would result in an inter- 

 locking of the two as of the teeth of two 

 hostler's grooming cards, whose handles 

 are pointed in opposite directions. The 

 fact that the structures are found in both 

 sexes would also seriously weaken the 

 theory that they are for sexual attraction. 

 The most feasible theory in my opinion 

 is, that they serve to hold the wings in 

 place when at rest, thus allowing a 

 relaxation of the muscles of the wings. 

 VVe can conceive how this might be a 

 great convenience to moths which close 

 the wings over the back. Of course, 

 the organs would be of no use to moths 

 which do not close their wings in this 

 way, as the Geometrina and Pterop- 

 horidae. and these do not have them. 



It should he stated, howexei', that they 

 are not found in all moths which do close 

 the wings; the Sphingidae lack them. 



The following is the result of an 

 extended search through the Heterocera 

 for these organs. The families are 

 mentioned in the order in which they 

 occur in Smith's List. It will be foimd 

 that \\hile the majority of moths have 

 the spiny area, some groups, some parts 

 of groups and some individuals lack 

 them. Families not mentioned have 

 not been examined. As previously 

 stated they are not found in the Sphing- 

 idae, although they were discovered in 

 every species which was examined of 

 the Sesiidae. The Agaristidae, Synt- 

 tomidae, Pyromorphldae, Ctenuchidae, 

 Xycteolidae and Lithosiidae all possess 

 them. Eiiplianessa mendica Walk., 

 formerlv classed with the Lithosiidae 

 lacks them ; but this species is now 

 considered by some, at least, to belong 

 to the Geometrina. The Arctiidae, 

 Lip;uidae, Limacodidae have them antl 

 the Notodontidae also with the excep- 

 tion of Afatelodes torrcfacta S. & A. 

 rhe Platyptfr\gidae and Saturnlidae 

 lack them. Of the Ceratocampidae, 

 Eaclcs imperialis (Dru.) and Dryo- 

 caiiipa rubicunda (Fabr.) lack them, 

 while Auisota senator ia S. & A. has 

 them. The Bombycidae, Cossidae, 

 Hepialidae and all the families of the 

 Noctuina. except the Brephidae have 

 them. As already stated they are not 

 found in the Geometrina.* Thev 



*The fact that the spiny area does not occur in Brephos 

 infans Moesch., one of the Brephidae, tends to confirm 

 the statement of Meyrick that " Breplios is a true member 

 of this group," (Geometrina^ 



