uthority as
Professor Dana, who, in the "American Journal of Science" (vol. 37,
Jan., 1864), proposed a classification of insects based on the principle
of cephalization, and divided the Hexapodous insects into three groups:
the first (Ptero-prosthenics, or Ctenopters) comprising the Hymenoptera,
Diptera, Aphaniptera (fleas), Lepidoptera, Homoptera, Trichoptera and
Neuroptera; the second group (Ptero-metasthenics, or Elytropters)
comprising the Coleoptera, Hemiptera and Orthoptera; while the Thysanura
compose the third group. Lubbock has given us a convenient historical
view of the opinions of different authors regarding the classification
of these insects, which we find useful. Nicolet, the naturalist who,
previous to Lubbock, has given us the most correct and complete account
of the Thysanura, regarded them as an order, equivalent to the
Coleoptera or Diptera, for example. In this he followed Latreille, who
established the order in 1796. The Abbe Bourlet adopted the same view.
On the other hand Burmeister placed the Thysanura as a separate tribe
between the Mallophaga (Bird Lice) and Orthoptera, and Gerstaecker
placed them among the Orthoptera. Fabricius and Blainville put them with
the Neuroptera, and the writer, in his "Guide to the Study of Insects,"
and previously in 1863, ignorant of the views of the two last named
authors, considered the Thysanura as degraded Neuroptera, and noticed
their resemblance to the larvae of Perla, Ephemera, and other Neuroptera,
such as Rhaphidia and Panorpa, regarding them as standing "in the same
relation to the rest of the Neuroptera [in the Linnaean sense], as the
flea does to the rest of the Diptera, or the lice and Thrips to the
higher Hemiptera."

After having studied the Thysanura enough to recognize the great
difficulty of deciding as to their affinities and rank, the writer does
not feel prepared to go so far as Dana and Lubbock, for reasons that
will be suggested in the following brief account of the more general
points in their structure, reserving for another occasion a final
expression of his views as to their classification.

The Poduridae, so well known by name, as affording the scales used by
microscopists as test objects, are common under stones and wet chips, or
in damp places, cellars, mushrooms and about manure heaps. They need
moisture, and consequently shade. They abound most in spring and autumn,
laying their eggs at both seasons, though most commonly in the sp