64 ON SOME SINGULAR LARVAL FORMS OF BEETLE. 
structure of the larva, with the same kind of eyes, antennae 
and legs; whereas the adult male is an elegant beetle with 
fully developed wings, large compound eyes, and often 
provided with beautiful fan-like or feathered antennae. 
It is possible and, I think, even highly probable that 
some of our “ trilobite ” larvae, the females, remain always 
in the form of larvae, and that the male larvae ultimately 
become transformed into beetles. Whether this be so or 
not might be decided in either of two ways. If it were 
found by the dissection of a sufficiently large number of 
specimens that some of them contained eggs or ripened 
ovaries, it would be clear that the specimens containing 
them were adult females. 
Again, if some of the larger individuals, such as might 
reasonably be supposed to be females, were kept alive, 
under observation, in a position in which the winged males 
could reach them, the advent of the males and their 
mating with the females might be seen. The advantage 
of any observation of this kind that may be made is that 
the male might be captured, and the identity of the species 
made possible. It is possible, of course, that the male 
also may retain always the form of the larva, but no case 
of the kind is yet known among the beetles, and I think it 
is very unlikely to occur. 
There are two special reasons which make me think it 
highly probable that the females retain the larval form. 
In the first place, when examining a larva of this type 
from Ceylon, I found it to be full of eggs, and the specimen 
was therefore presumably an adult female. But there was 
a slight element of uncertainty in this case. The eggs 
might have been deposited there by some parasitic insect, 
though I consider this extremely unlikely owing to the size 
and the large number of the eggs. 
In the second place, I have found that all the specimens 
of the genus Lyropceus , Waterh., in the British Museum 
Collection, though certainly not numerous, are all males; 
so that the females, unless exceptionally rare as com¬ 
pared with the males, must be of an entirely different 
form. I know of but one species (as yet undescribed) of 
this genus from Borneo, and of that species I have seen 
only one specimen. But the range of distribution of the 
genus corresponds pretty closely with that of the larvae 
whose identity it is so desirable to know. 
In one point of structure these larvae differ from all other 
known beetle larvae. They have a pair of very distinct 
