264 B. GRASSI AND A. SANDIAS. 
completely pilose joints in the larve and nymphs of perfect 
insects. During this stage both of the latter may undergo 
the same fate as in the preceding stages, becoming soldier 
larvee, larvee of substitute royal forms, or, if already larve of 
perfect insects, nymphs. 
Both the larvee of perfect insects or nymphs may pass with- 
out change to the stage in which the antennz possess seven- 
teen joints. During this stage both may become larve of 
soldiers or royal substitutes. If this does not happen the 
nymphs acquire larger wing rudiments, and the larve of perfect 
insects become nymphs (Pl. 16, fig. 4). 
Before proceeding further it is desirable to give a fuller 
definition of the term nymph. 
It may be applied to such examples as are 8 or 10 mm. in 
length, with sixteen or seventeen antennal joints, and with 
wing-rudiments easily distinguishable by the naked eye. The 
expression, it must be observed, is incapable of precise defini- 
tion, inasmuch as there are no characters in insects with an 
incomplete metamorphosis which distinguish a larva from a 
nymph, except the wings, which have already begun to develop 
in larve of a certain age. It might possibly be adopted as 
connoting the earliest rudiments of wings, but this presents 
the difficulty that they are not easily detected. I therefore 
follow the terminology of Lespés and Hagen, and conventionally 
indicate as nymphs those individuals which have the beginnings 
of the wings readily visible to the naked eye. 
From the account just given it follows clearly that large 
soldiers are derived from the large soldier larvze, just as the 
moderate-sized and small soldiers originate from larve of 
corresponding sizes, and that the large soldier larve have arisen 
in their turn from undifferentiated larve with fifteen antennal 
joints, or from larvee of perfect insects with antenne of fifteen, 
sixteen, or seventeen joints, or lastly also from nymphs. The 
latter, possessing sixteen or seventeen joints, may be trans- 
formed into soldier larve, and subsequently become large 
soldiers in which the wing-buds can be distinctly made out 
with the naked eye (Pl. 16, fig. 26). At a later period these 
