1974] 
Parsons — Pterothorax of Cryphocricos 
49 
ventral phragmal process, is absent. In this region, consequently, the 
part of the metanotum on which Muscle 70 originates borders 
directly on the scutellar lobe. This atypical intersegmental boundary 
appears to grow anteriorly during post-ecdysial development. 
Figures 3 and 4 could be interpreted in tWo other ways, either 
( 1 ) that there are no post-ecdysial changes in skeletal boundaries 
and that in Figure 4 the anteriormost fibers of Muscle 70 have 
simply shifted anteriorly, onto the mesonotum, or (2) that a. post- 
notum is present lateral to the phragmal process and is represented 
by the fold (fig. 3; F) upon which the anteromedial fibers of Mus- 
cle 70 attach. According to this second view the origin of the muscle 
has shifted from the metanotum onto the homologue of the thickened 
postnotum of macropterous Cryphocricos (fig. 2; PN). Conse- 
quently, it is the boundary between the mesothoracic scutellum and 
postnotum (secondary intersegmental boundary of Snodgrass, 1935) 
which appears to grow anteriorly after ecdysis, rather than a primary 
intersegmental boundary. Neither of these two interpretations has 
been adopted here because in Cryphocricos and at least two other 
genera of Naucoridae post-ecdysial skeletal growth takes place in 
the pterothoracic pleuron (see p. 46) and almost certainly occurs 
along the primary intersegmental boundary between the metathoracic 
episternum and the mesothoracic epimeron. 
Degeneration or absence of the three mesothoracic indirect flight 
muscles, and consequent loss of the ability to fly, is a common oc- 
currence among Hydrocorisae (Larsen, 1950). Extreme alary di- 
morphism such as that of Cryphocricos is much less common. Larsen 
(1950) studied Aphelocheirus ( Aphelocheiridae) which has both 
micropterous and macropterous forms, and found that the size and 
shape of the ventral phragmal processes, upon which two of the 
indirect flight muscles attach, differ in the two types. Similar dif- 
ferences in the phragmal processes occur in flying and flightless 
Ilyocoris (Naucoridae; Larsen, 1970). Both forms of Ilyocoris 
possess forewings and hindwings of normal length, but most in- 
dividuals lose their indirect flight muscles soon after the final moult. 
Larsen did not, however, observe post-ecdysial skeletal changes, ab- 
sence of the lateral part of the second phragma, or loss of a portion 
of the mesothoracic postnotum in either Aphelocheirus or Ilyocoris. 
All these features appear to occur in micropterous Cryphocricos. 
Acknowledgements 
I wish to thank Fritz Plaumann (Nova Teutonia, Brazil) for 
