ON THE STRUCTURAL CHARACTERS OF LEPIDOPTEROUS LARV/E. 197 



on the raesothorax consist of but two above the lateral anteriorally 

 situated one, or, if there are three, the lower of the three is rudi- 

 mentary. This type appears in the ArctiidaB, and their derivatives the 

 LithosiidpB and Syntomidfp, as well as in the Apatelid Noctuids, 

 PericopidfB, etc. In the other type there are three thoracic warts 

 above the lateral wart, the upper one of the three rarely becoming 

 rudimentary. Secondary hairs are often present, and in the highest 

 forms may become predominant over the warts. The hairy Noto- 

 dontians, Liparidte, Lniionia, Bombycidae and Lasiocampidns, illustrate 

 this type. Home of these groups are much specialised, and their 

 structure can only be determined in the earliest larval stages. 

 EndroDiis is an aberrant form, probably belonging here. The thoracic 

 warts do not correspond to the type in stage i, and afterwards they 

 soon disappear ; but, judging from the Australian Chelcjitcn/.r, which 

 seems closely allied, we have to do with a degenerate Lasiocampid 

 form. Considering the size of this group, the larval characters run 

 very evenly, and it is only in the most specialised species of the 

 Lasiocampid stock that any doubt or confusion is likely to arise. 



II. The LARVJi OF THE Saturnians. — The larva) of the Saturnians 

 are characterised by the union of tubercles iv and v, and the absence 

 of the subprimary setjc. There is a strong tendency to the hyper- 

 trophy of all the tubercles, except ii, vii and viii, of abdomen, and to the 

 union of the two tubercles i of the 8th or 9th abdominal segments, 

 into a single unpaired dorsal process. In the simplest forms the 

 setfe are single in stage i, though borne on elongated tubercles. 

 Nearly all species have warts in the later stages, often much elongated 

 or hypertrophied. The warts may be variously modified. I know 

 of no species in which the single haired condition persists. Secondary 

 hairs are often present. The group divides into two large types, and 

 one of these into smaller ones, as follows : — 



I. — A single dorsal tubercle on 9th abdominal segment. 



(1). — A pair of tubercles on the anal plate . . . . Citheroniidae. 

 (2). — No tubercles on the anal plate ; setae con- 

 verted into stinging spines Hinuilencidac. 



II. — No single tubercle on 9th abdominal segment Satnrniidcu'. 



The first two families are the lowest, and are only found in 

 America. In the CitheroniidiB there is a primitive first stage ; the 

 tubercles are elongated and branched, later several haired. All the 

 genera, except Anisota, have the unpaired tubercle on the 8th 

 abdominal segment. The Hemileucidte difi'er in the loss of tubercles 

 on the anal plate, and the conversion of the setae of the warts into 

 strongly stinging poisonous spines, both characters of specialisa- 

 tion. The Saturniidae have a world-wide distribution, and a more 

 considerable range in modification. In at least one genus {Satuniia) 

 the dorsal tubercles of segment 8 are not consolidated. Most of 

 the larvae have short tubercles, with not many hairs, a few, or even 

 many secondary hairs. There is no primitive first stage, so far 

 as I know. In Crinda the warts are practically absent, and the 

 larva is clothed with soft secondary hairs. Aijlia is an unique form, 

 with a quite generalised condition of the tubercles at first, but later 

 they are entirely lost. The African forms have a tendency to smooth, 

 sharp, thorn-shaped tubercles without secondary setae. Utota presents 

 a curious structure of many little smooth flattened warty excrescences. 



