1925 ] Mystery of “ Trilobite Larvce” Definitely Solved 129 
adults retaining infantile characters and can therefore be termed 
neoteinic in the definition of Giard (1905). The males on the 
other hand are well developed beetles probably hitherto un- 
described but in all essential characters normally developed 
Lycids. 
The female has so completely reduced her metamorphoses 
that in her external features, she is perfectly larviform. No 
marked pupa or imago-stage exists. As a worm-like creature 
she crawls sluggishly about on the ground and dies after having 
deposited her numerous eggs. Copulation and oviposition take 
place in a quite normal way. The female has specialized in the 
direction of larger size, premature development of the sexual 
organs and in reducing the normal metamorphoses to an ab- 
solute minimum. 
It seems certainly strange that the female after the last 
ecdysis remains whitish and unpigmented. A close examination, 
however, shows that a diffuse casting of skin takes place after 
the development of the sexual organs, or in most cases after 
oviposition, when the body shrinks together and therefore the 
thin transparent skin becomes more conspicuous. (Plate III Fig. 
2a). This partial casting of the skin seems to be more or less 
confined to the dorsal side and is probably the last reminiscence 
of a former regular pupal stage, which we must suppose the 
female to have possessed during earlier geological periods when 
it was more similar to the male and not yet so highly differentiated 
in the way of retrograde development. 
It deserves in this connection to be mentioned that many, 
if not all of the normally developed Lycids show a distinct ten- 
dency to retain the last larval skin when pupating. When in 
Borneo I bred hundreds of the gregarious larvae of Lycostomus 
gestroi Bourg. They all kept their skin when pupating. The 
advantages of this are apparent. The larvae are black 
with bright yellow markings, which serve as warning colors. 
Their principal enemies, birds, reptiles and carnivorous insects 
know by experience their nauseous properties and a Lycostomus 
larva is therefore never attacked. The insect makes use of the 
well-known warning coloration to protect the whitish-yellowish 
pupa, by keeping the larval skin as a cover. The larval skin 
