1931 ] 
Structure of Notiothauma reedi 
3 
orpidse, in which the structures in question may become 
hugely developed. In Panorpa stigmalis (fig. 27) the notor- 
gan n has become elongated and extends posteriorly to the 
cone po, which is located further back in segment four, 
while in Neopanorpa cornuta (fig. 26) the orthogenetic 
tendency for the notorgan n to become further elongated 
becomes more pronounced, since in the latter insect (fig. 
26) the notorgan n projects posteriorly over the fourth 
tergite and nearly reaches the middle of the fifth tergite. 
In such Panorpids as P. takenouckii (fig. 29) the ortho- 
genetic tendency for the notorgan n to become more and 
more elongated, reaches its culmination. Since Notiothauma 
furnishes the only starting point, among the lower Mecop- 
tera, for the development of such a notorgan (n of fig. 1 
and 5) this very clearly indicates that Notiothauma is the 
most like the ancestor of the Panorpidse. 
On the fifth tergite of Notiothauma there occurs a re- 
markable median unpaired tergal process labelled mo in 
figs. 1 and 5. This process is apparently peculiar to Notio- 
thauma, although a shorter process, resembling it in some 
respects, is borne on the sixth (instead of the fifth) ter- 
gite of P. cornigera, shown in fig. 32. This process of the 
sixth tergite of P. cornigera, abuts against the dorsal por- 
tion of the seventh abdominal segment, when the end of 
the abdomen is turned forward on top of the abdomen, 
while in Notiothauma, the tips of the genital styles st of 
figs. 1 and 5 apparently lie on each side of the median pro- 
cess mo when the tip of the abdomen is turned up over the 
top of the abdomen of the male insect. 
The sixth abdominal tergite of Notiothauma bears a pair 
of lateral tergal processes labelled be in fig. 1, which are 
somewhat suggestive of the paired lateral tergal processes 
borne on the sixth tergite of Neopanorpa cornuta shown 
in fig. 26. Dorso-mesad of the processes be on the sixth 
tergite of Notiothauma shown in fig. 1, are two smaller 
processes (paired) which may have developed as enlarged 
“setigera” or seta-bearing protuberances of the segment. 
These setigera bear dinotrichia or powerful bristles like 
those shown on the seventh and eighth tergites in fig. 1, 
