.MEMDIKS OF THE NATIONAL ACADEMY OF SCIENCES. 21 



"111 other geiK'iu of this fuiiiily, as the species of Ociiiara. in which the body is slender, tliere 

 is a caudal horn. In O. siynifera there is a well-developed caudal horn, while the body Ls 

 humped on the second thoracic, second and fifth abdominal segiiients. Indeed, it bears a close 

 resemblance in general appeai-ance to certain geometric or measuring worms, such as Ennomos, 

 Eutrapela, Eugonia, etc. 



"It is worthy of notice, as bearing on the u.se of these horn-like tubercles as offensive struc- 

 tures, that Captain Hutton states that the extremity of the horn is retractile and is generallj- 

 withdrawn into the lower part as a sheath; when the animal is about to molt, or is disturbed 

 and irritated, the summit of this spine is exserted. and instead of being brown, like the base, is 

 whitish; when exserted the whole stands erect, slightly inclining backward." 



Horsfield and Moore figure the larva of O. diltx-ttda of Java as having a horn. 



The caudal horn of the Sphingids-. — Much has been written on this subject. In 18S2 ]\Ir. 

 Meldola, in the appendix to his translation of "Weismann's "Studies in the theory of descent," 

 calls attention to the caudal horn of sphinx larva\ mentioning that in the young larva? it is " freely 

 movable," adding: "It is possible that this horn, which was formerly possessed by the ancestors 

 of the Sphingidie, and which is now retained in many genera, is a remnant of a flagellate organ 

 having a similar function to the head tentacles of the Papilio larva> or to the caudal appendages 

 of Dicranura." 



Poulton (1884) concludes that the forking of the horns is a primitive character and observes 

 that it is movable in the two first stages of 6'. Ii(ji(i<fri and under the control of the animal's will. 

 He also quotes notes from Mr. K. Trimen on the young larva of LoplioKtethu^ di/moJin/'f' Angus, in 

 which it is stated that the anal horn is, like the dorsal thoracic spines, "distinctly forked" at the 

 extremity. Mr. Meldola adds that "the forked caudal horn in the young larva of this species is 

 of interest in connection with the similar character of this appendage in the young caterpillar of 

 Ilijloieus pinasti'i^^ (p. .527). 



The caudal horn of the fully grown larva of Lophoxtefhnx duiiiollnii, which is well figured 

 by Lieut. Col. J. il. Fawcett." differs from that of all other known sphingid caterpillars in being 

 a solid chitinous spine, sharp, not forked, and with several seta% being in fact, judging by the 

 tigui-e, no stouter, longer, or differing in any respect from the thoracic horns. 



Wilhelm ]\Iiiller. in 1886, at the close of his memoir, figures the end of the body of the larva 

 of Diloptonota and discusses the caudal horn of the Sphingidse, considering that it has the same 

 origin as the unpaired horn of the Saturniida. remarking: " Both have arisen from the supporting 

 structures [tubercles] of the two bristles upon segment IL" He concludes that the caudal horn of 

 the Sphingida> is the remains of another armature perhaps referable with that of the Saturniidre of 

 the present day to a common source, so that the caudal horn of the Sphingidie and the caudal 

 spine {Ds horn) of the Saturniidiv are in the fullest sense homologues. 



The present writer has paid especial attention to the double nature of this tubercle in the dif- 

 ferent groups and genera of the Ceratocampidic. Hemileuciihe, and Saturniida?, the facts being 

 stated in the course of the description of the larvie in diflenMit stages and affording strong proofs 

 of its origin from the fusion of the two tubercles /. 



Besides the caudal horn of Ceratomia. already descriljed. I have previously stated'' that in 

 stage I of Paonias exciecatu.^ the caudal horn is distinctly forked at the tip. and that in stage III 

 it ends in two tubercles. In Sphiii.c l-almiie in its second or third stage the horn ends in three 

 or four tubercles, but in stage IV ? there are no definite traces of a fork. In a Sphinx found on the 

 larch the horn is smooth, but ends in two fine seta?. In a lot of freshly hatched Sphinx larva^ of 

 an unknown species the horn is distinctly forked. 



In a full-grown Sjdiiit.r eln-rxix the end of the horn is smooth and undi\ ided. PI. XLII. 

 Fig. 3, represents the end of the caudal horn of Paaniux nn/ops^ the tip ending in two rounded 

 smooth tubercles without a seta, though the rounded spiuules below each bear a distinct seta; 

 a represents the tip as seen from the end, showing the rounded ends of the fork. 



« Trans. Zool. Soc, London, XV, April, 1901. 



(■Proc. Boston Soc. Nat. Hiet. XXV, p. 10:!, footnote, 18f)0. Conii)are ul-so C. M. Piepers, Ueber das Horn der 

 Sphingiden-Raupen, Tijdsclir. v. Ent., XL. 



