20 .MK.M()IK> OF THE NATIONAL ACADEMY OE SCIENCES. 



In tilt' riiial ~tauo tlic liorn sliows >onie reduction, bi'ino- shorter tliun in the previous sta^e. 

 There is no tiMulcney to fusion of tlie two dorsal warts on the ninth abdominal sej^nient. 



The caudal horn in the Honibycidie shows no resemblatice or affinity to that of the Ceratoeam- 

 pida?. and here I may state that the small fan)ily Bombycida' has no relationship with the Cerato- 

 cainpid* or Saturniidiv: on the contrary the family is intimately related liy its larval and pujxil 

 characters with the Lasiocampida\ and I am inclined to the view that the Bombycidte have 

 actually oriu-inated from the Lasiocampidie. their larvie having underj^one a process of acceleration, 

 while the moths have been modified by atrophy of the veins and mouth-parts. On comparino- the 

 caudal horn of Bomhi/.r mori with that of Gastrojxicha (Epicnaptera) Aincricaxd it was found to 

 be similar in structure and armature, though that of Epicnaptera is broad, short, flat, and conical. 

 On further comparison of the fully-grown larva' of the two genera I was surprised to find how 

 nearly allied they are. The head of Bdmhyx mwi (PI. XLIV, tig. 5) is of the same peculiar shape 

 as in the Lasiocampida?, and densely clothed with long hairs; they are alike also in the nature 

 of the tergal region of the prothoracic segment, though li. iKor! is without the prominent lateral 

 tubercles so diagnostic of the larva^ of Lasiocampida' and Lymantriida'. In the ninth segment as 

 regards the shape of the suranal plate and of the anal legs, B. mori is closely similar to those of 

 Epicnaptera. I conclude, then, that the Bombycidie lieing essentially lasiocampids in their 

 larval characters, as imagoes the group l)ecame modified by retrograde development and formed 

 a downward bent side-l)ranch of the lasiocampid stem. We have here a clear example of the 

 evolution by atrophy of one family from another. Dyar" states that the warts of B. mor! are 

 '•true warts of the typical lasiocampid pattern.'" He plates the family near the Lymantriida\ 

 To Professor Sasaki '' we are indebted for an account, with figures, of the first stage of the wild 

 silkworm of Japan, which Sasaki identifies as TheophUa /n a iidnrrna, and its descendant or deriva- 

 tive Boiiihi/.r III"!-/. In both of thesis forms there is already in stage I a single median wart 

 on the eighth alxlominal segment. This shows that the larva has undergone, just as in Epic- 

 naptera. before hatching an acceleration of development as regards this pair of warts. After the 

 first molt the caudal horn is developed. Sasaki observes: "After the second stage there are no 

 marked changes iu both color and markings till the larva becomes mature." 



I have always supposed that the Bombycida were more nearly allied to the Saturniida. since 

 they have but three branches to the median vein and atrophied mouth-parts, but we now see that 

 these reduction characters are not diagnostic of any particular group of families, but may occur 

 in any group as the result of disuse and loss of power of flight in the imago. Here, as elsewhere 

 in the insect and animal kingdom, the larval or postembrvonic character as a rule, though there 

 are exceptions, aflord the truest guide to the phylogeny of a group. 



It is interesting to observe how the armature of certain species of Bombyx and sillied genera 

 repeats in general ajjpearance that of the ceratocampid genus Adelocephala, etc., though the 

 resemblances are surely cases of convergence, due perhaps to their living on trees whose twigs 

 are either tui)erculated or spiny. 



The two most striking cases of mimetit' analogy, parallelism, or convergence are seen in the 

 larva of Th,i'i>h')l,i Iniltinn. described and flgured by T. Hutton. In the newly hatched cater- 

 pillar there is. he says, '"a small anal tul)ercle on the penultimate segment; thus far there is 

 scarcely a diflerence between it and the young Chinese worm."' This is evidently the same as 

 the incipient caudal horn of the larva of the .same stage of Bomhyw inandai'inu and B. nmri. 

 After the flrst molt the warts l)ecomc converted into short, conical, fleshy tubercles or spines. In 

 the mature larva "thi're are two dorsal rows of long, black, slender, and sharp-pointed spines, 

 c(>mm(>ncing with the flfth [second abdominal] segment. While the median spine is thus fused 

 or double, the warts on the ninth segment of stage I become long spines about as large as the 

 caudal horn. 



" Oil thf larva' of tlu- lii-lirr IJoiiiliyces. Proc Rost. Soo. X.it. ITist., XXVII, p. 140, 1896. 



*(.)ii the affinity of our wiM \\\v\ iloinestic i<ilk\vorm.-<. Annotntione.'i Zoolojiirae Japonen.'ies, ii. Part II, June, 

 1898. pp. 33-40. 



