354 
INSECTA. 
common species lias been compared to a little Fish. The antennse 
are setaceous and usually very long. The mouth is composed of a 
labrum, of two almost membranous mandibles, of two bipartite jaws, 
with a palpus consisting of five or six joints, and of a quadri-emar- 
ginated lip bearing two quadri-articulated palpi. The thorax is 
formed of three pieces ; the abdomen, which is somewhat narrowed at 
its posterior extremity, is furnished along each side of the venter 
with a range of small appendages, supported by a short joint, and ter- 
minating in silky points, the last of which are the longest ; a sort of 
scaly compressed stylet, composed of two pieces, issues from the anus; 
then come the three articulated setae, which are extended beyond 
the extremity of the body. The feet are short and frequently have 
very large strongly compressed coxae resembling scales. 
Several species conceal themselves in the cracks in the frame work 
of windows, under damp boards, in wardrobes, &c. Others retire 
under stones. 
These Insects run with great velocity ; some of them by means of 
their caudal appendages are enabled to leap. They are divided into 
two subgenera. 
Machilis, Lat , — Petrobius, Leach. 
Eyes very compound, almost contiguous, and occupying the greater 
part of the head ; body convex and arcuated above ; abdomen termi- 
nated by small threads for saltation, of which the middle one, placed 
above the two others, is much the longest. 
The maxillary palpi are very large, and have the form of small 
feet. The thorax is strangulated, the first segment smaller than the 
second and arched. 
These Insects leap well, and frequent stony and enclosed places. 
All the species known belong to Europe *. 
Lepisma, Lin . — Forbicina, Geoff., Leach. 
Eyes very small, widely separated, and composed of a small num- 
ber of granules; body flattened, and terminated by three threads of 
equal length, inserted on the same line, and of no use in leaping. 
Their coxae are very large. Most of the species inhabit the inte- 
rior of houses. 
L. saccharina; Forbicine plate, Geoff., Insect., II, xx, 3; 
Schaelf., Elem. Entom.,lxxv. Four lines in length ; of a silvery 
and somewhat leaden hue, and immaculate ; originally, it is said, 
from America, now very common in houses in Europe. 
L. vittata,¥ah. Body cinereous, dotted Avith blackish ; four 
streaks of the same colour along the back of the abdomen. 
Other s^jecies are found under stones. 
* Lepisma pohjpoda, L. ; L. saccharina, Vill., Entom. Lin., IV, xi, I; Roem. 
Gener. Insect., XXIX, 1 ; Forbicine cylindrique, Geoff. ; — Lepisma thezeana, Fab. ; — 
Petrobius maritimus, Leach, Zool. Miscell., CXLV. 
