4 
28 
eg. in Saturnia pavonia. The original tubercles are here, even in 
the newly hatched larva, changed into verrucae and in the later 
instars into scoli. The only exception is seta dorsalis on the prothorax, 
which remains a single seta (fig. 3). 
Type Ib. A final stage, almost identical with the former is found 
in Lymantridae = Liparidae. But here it is not the subdorsal seta 
or verruca which disappears, but the dorsal one. The poststigmal 
verruca associates with the suprastigmal one, but not completely, 
as even in full grown caterpillars the original duplicity remains 
perfectly visible, the two halves being divided by a furrow (fig. 4). 
Type Il. At first sight meso- and metathorax seem to possess a 
setal pattern different from that on the segments of the abdomen 
(fig. 5). 
If we draw a line over these thoracic ‘segments which crosses 
the stigmata of prothorax and abdomen, three setae on each of 
these segments are found above it, arranged in a vertical series. 
This group of setae is near the oral border of the segments. I con- 
sider them to be the dorsal, dorsolateral and suprastigmal seta. 
Nearly in the same series the seta prostigmalis is found, as is 
clearly proved in those cases where a vestige of the stigma is present.) 
Then the rudiment lies near the caudal border of the segment in 
the same position as the stigma of the prothorax. Sometimes it is 
vepresented by a pigmented spot (Porthesia chrysorrhoea, Zeuzera 
pyrina) or by a verruca (Arctia caja, Sericina telamon) and in other 
cases the tracheal system is visible through the skin and shows a 
distinct inflation on the corresponding place (Pieris brassicae and 
P. napi). Beneath the prostigmal seta the infrastiymal one, and in 
some cases the /asa/ ones are found. As all these setae are arranged 
in a row, the type of their arrangement seems to be exceedingly 
simple. 
By the above mentioned writers these setae are homologized in 
very different ways, as is demonstrated by the tabulated survey, 
given by Frackrer on page 40. 
In comparison with the abdominal, this type // in the first place 
shows a reduction. by the suppression of the superior and inferior 
subdorsal setae. The former however sometimes remains visible. 
(Pieris napi). Moreover the poststigmal seta is generally absent. 
I explain this reduction as a consequence of the situation of the 
stigma near the caudal border of the thoracic segments, which 
hindered the complete development of the posterior row of setae. 
I hope to give full details in my next paper. 
1) Even when this vestige is the wing “anlage” the seta s. prostigmalis remains. 
