94 BRISTLE-TAILS AND SPRING-TAILS. 
. palpi vary in these groups of insects is well known. The galea 
sometimes forms a palpus-like appendage. Now these three lobes 
` may be easily distinguished in the maxilla of Lepisma. The pal- 
pus instead of being directed forward, as in the insects mentioned 
above (in the pupa of Ephemera the maxilla is much like that 
of Lepisma), is inserted nearer the base than usual and thrown off 
at right angles to the maxilla, so that it is stretched out like a leg, 
and in moving about the insect uses its maxille partly as sup- 
ports for its head. They are very long and large, and five or six- 
jointed. The galea, or middle division, forms a simple lobe, while 
the lacinia has two large chitinous teeth on the inner edge, and 
internally four or five hairs arising from a thin edge. 
The labium is much as in that of Perla, being broad and short, 
with a distinct median suture, indicating its former separation in 
embryonic life into a pair of appendages. The labial palpi are 
three-jointed ; the joints being broad, and in life directed back- 
wards instead of forwards, as in the higher insects. 
There are four American species of the genus Lepisma in the 
Museum of the Peabody Academy, which contains, so far as we 
are aware, the only collection, small as it is, of Thysanura in 
the country. Besides the common ZL. saccharina? (Pl. 1, fig. 1) 
there are three undescribed species ; one the heat-loving form, per- 
haps an imported species, found in a kitchen in Salem, and appar- 
ently allied to the L. thermophila Lucas, of houses in Brest, 
France; and two allied forms, one from Key West, and another _ 
from Polvon, Western Nicaragua, collected by Mr. MecNiel. These 
three last species are beautifully ornamented with finely spinulated 
hairs arranged in tufts on the head; while the sides of the body, 
and edges of the basal joints of the legs are fringed with them. 
The most complicated genus, and which stands at the head of 
the family, is Machilis (Pl. 1. figs. 8, 9), of which there are spec 
imens in the Museum of the Peabody Academy, from Albany, 
N. Y., Virginia, and Oregon, indicating two species. They affect 
dry places, living under leaves and stones. They all have rounded, 
highly arched bodies, and large compound eyes, the pair being 
united together. The maxillary palpi are greatly developed ; but 
the chief characteristics are the two-jointed stylets arranged in nine 
pairs along each side of the abdomen, reminding us of the abdom- 
inal legs of Myriapods. The body ends in three long bristles, 
asin Lepisma. The interesting genus Nicoletia stands at the bot- 
