300 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
tainty the line of development of this extensive order from the Cam- 
podea type. There are two series of facts which seem to us to throw 
light on the subject. 
First, the form of the free, active larvae of the carnivorous groups of 
beetles. The larvaeof theCarabidae, Dytiscidae and Staphylinid* appear 
to us to beon the whole more nearly allied to what was probably the primi- 
tive form of Coleopterous larva than those of any other families. This 
ancestral Coleopterous larva was probably directly related to theOampo- 
dea-form ancestor of the Hexapoda. The general form of the body, the 
homonomous segments, the free, biting, toothed mandibles, the well-de- 
voloped one- or two-lobed maxillae with their three-jointed palpi, and the 
well-developed second maxillae (labium), also the four-jointed antennae, 
and the presence of ocelli, while showing that the existing carnivorous 
larvae are the most specialized and highly developed, also show that 
they have undergone the least modification from the primitive type of 
Coleopterous larva. In the scavenger larval forms, as the Silphidae, Der- 
mestidae and allied families, the mouth-parts begin to be modified and 
less developed, and the form of the body undergoes a change, becoming 
thicker and with less developed feet. 
In the Elateridae and Scarabaeidao, which in general are phytopha- 
gous, wo see a still more decided change; the body becoming cylindrical 
and the mouth-parts more aberrant. 
In the wood-boring Buprestidae and Cerambycidae, and in the leaf- 
eating Chrysomelid larvae, we witness a decided departure from the 
carnivorous type; the mouth-parts show a tendency to become more or 
less aborted, the legs are frequently wanting and the body more or less 
maggot-like. Finally, the tendency to agradual degradation and atrophy 
of thq head, mouth-parts and legs culminates in the grubs of the weevils 
(Curculionidae and Scolytidae), placing them at the foot of the Cole- 
opterous series, and shows that they have undergone the greatest modi- 
fication of form, and have become adapted to conditions the most unlike 
those which constituted the environment of the primitive Coleopterous 
larva. 
The relative form of the maxillm appears to be a good index as to the 
general development of the body in the different groups of Coleoptera, 
especially those standing above the wood-boring families. The facts 
may, for convenience, be arranged in the following form: 
Cicindelidce . — Maxilla with a maxillary lobe or mala proper ending in 
a 2-jointed appendage which is longer than the 3-jointed palpus. (An- 
tennae 4-jointed ; 3 ocelli.) 
Oarabidai . — Maxilla with the mala 2-jointed; maxillary palpus 4- 
jointed. (Antennae 4-jointed, bifurcate; ocelli often present.) 
DytiscidoB (and Hydradophaga in general). — Maxilla with the mala 
absent; the palpi 4 jointed. 
The maxilla in the aquatic forms of the Carabid typo is only a modi- 
fication of the Geodephagous maxilla; the terminal palpal joint being 
acute and raptorial. 
