12 THE BUTTERFLIES OF NEW ENGLAND. 



Tlie thoracic and abdominal segments also differ frequently in the posi- 

 tion of the armature borne by the segments, and whether these consist of 

 sim[)le or compound spines, tubercles, bristle-bearing papillae, or fleshy 

 filaments, they are usually arranged in several definite longitudinal series ; 

 but such series are frequently broken at the division between the thoracic 

 and abdominal segments, a subdorsal abdominal series, for instance, 

 becominor laterodorsal on the thoracic segments ; sometimes also a series 

 is limited to one or the other region. On this account and in order to give 

 greater precision to descriptions of the parts of caterpillars, I have here 

 adopted a uniform nomenclature to designate the precise height on the body 

 at which the serial appendages occur, as follows : dorsal or mediodorml 

 for a line passing down the middle of the back ; ,sti(jinaf(d for a line pass- 

 ing along the spiracles ; lateral for a line midway between these two ; lat- 

 erodorsal for a line midway between the mediodorsal and the lateral ; 

 subdorsal for a line between the mediodorsal and laterodorsal ; sujrralateral 

 and infralateral for lines just above and below the lateral ; laterostigmatal 

 for a line midway between the lateral and stigmatal ; suprastlgmatal and 

 infrastiyniatal for lines just above and below the stigmatal ; ventral or 

 medloventral for a line passing along the middle of the belly; subventral 

 for a line close to it ; lateroventral for one still further removed from the 

 medloventral ; and ventrostigmatal for any between this and the infrastig- 

 niatal line. The necessity for precision is greatest above the spiracles, for 

 the armature of the caterpillar is found, as would be expected, almost 

 entirely upon the upper surface of the body. All of our butterfly caterpillars 

 are clothed with hairs, although in the Papilioninae and Euploeinae they are 

 so short and delicate as to leave the creature a naked a})pearance, and in 

 addition to this most of them have other tegumentary appendages in difler- 

 ent parts of the body ; their arrangement affords admirable generic char- 

 acteristics which ha^e not hitherto l)een sufliciently appropriated. 



In this connection it should be stated that in the character of the arma- 

 ture both of the head and body enormous difterences Avill be found between 

 the young and mature larvae of the same species, — difterences which until 

 recently appear to have been entirely overlooked. In fact juvenile cater- 

 pillars in their first stage may be tersely said to dift'er generically from 

 themselves at a mature epoch. In some the change becomes an abrupt 

 one at the first moult ; in others it is brought about by comparatively 

 slight alterations at successive moults. The difterences consist, for exam- 

 ple, in the presence in some juvenile larvae of pa[)illae, emitthig hairs, some- 

 times of excessive length, arranged in definite series, all of which entirely 

 disappear at maturity, the body being then clothed only with short uni- 

 formly distributed hairs seated on papillae ; or, to take another instance, 

 the head of a newly born caterpillar, covered with several large tubercles 

 which entirely destroy the regularity of its contour, gives place to a well- 



