1925] Mystery of “ Trilobite Larvce” Definitely Solved 147 
possessing many-jointed (10-11) antennae, compound eyes and 
two claws, but lacking all traces of elytra and wings and therefore 
extremely larviform. 
It is in this connection of interest to note that in the female 
also a reduction of the antennae is noticeable. These show only 
ten joints, the apical one being reduced to a small appendage 
only, reminding of the small accessory appendage often found 
in the larval antennae. 
In some cases even a further reduction seems to take place. 
According to Grawshay “the antennae of the female are normally 
composed of 10 joints (omitting the supplement) but the ninth 
joint is often imperfectly formed being sometimes confounded 
with the preceding one so as to be scarcely visible, and some- 
times entirely absent.’ ’ This deformity may even appear in 
different degrees in the two antennae of the same insect. The 
Drilids therefore show a much greater degree of retrograde 
development than the Lampyrids. 
The extensive group of the Telephorids shows as a rule quite 
normal conditions. Both sexes are equally well developed and 
typically predaceous, in this latter respect agreeing with the 
larvae of the two previously mentioned groups. A strikingly 
exceptional type, however, is the remarkable American group 
Phengodini, where the sexes differ greatly from each other. 
Thanks to Haase’s excellent paper (Zur Kenntnis von 
Phengodes, Deutch. Entom. Zeits. 1888) we know that the Phen- 
godes female has developed in a retrograde direction to an ex- 
tremely larva-like creature. The male on the other hand is an 
elaborately developed beetle with highly specialized antennae. 
According to Haase and Riley the female differs from the larva 
only by having “more feeble mandibles and tarsi” than the 
larva. It passes, however, a distinct pupal stage as is also cor- 
roborated by Mr. H. S. Barber in a letter to me. 
In Sharp’s “Insects” of the “Cambridge Natural History” 
the following startling statement about Phengodes is found: 
“There is no reason to doubt that Haase was correct in 
treating the insects we figure as a perfect insect; he is, indeed 
corroborated by Riley. The distinctions between the larva and 
female imago are that the latter has two claws din the feet instead 
