there is still much difference of opinion. It must also be 
observed that Prof. Westwood omits the parasitic Ano- 
plura, as well as the Thysanura and Collembola. 
Orders of Insects according to Westwood. 
I, HYMENOPTERA . Bees, Wasps, Ants, &c, 
2. Strepsiptera . . Stylops, Zenos, &c. 
3. COLEOPTERA . . Beetles, 
4. Euplexoptera . . Earwigs. 
5. ORTHOPTERA . . Grasshoppers, Crickets, Cock- 
roaches, &c. 
6. Thysanoptera. Thrips. 
7. NEUROPTERA . Ephemeras, &c, 
8. Trichoptera Phryganea. 
g. DIPTERA. . . . Flies and Gnats, 
to. Aphaniptera. . . Fleas. 
11. HETEROPTERA . Bugs. 
12. HOMOPTERA 
i Aphis, Coccus, &c. 
13. LEPIDOPTERA 
Butterflies and moths. 
Of these thirteen orders, the eight which I have placed 
in capital letters, namely the first, third, fifth, seventh, 
ninth, eleventh, twelfth, and thirteenth, are much the most 
important in the number and variety of species. The 
other five are comparatively small groups. The Strepsip- 
tera are minute insects, parasiticon Hymenoptera. Rossi, 
by whom they were discovered, regarded them as Hymen- 
opterous ; Lamarck placed them among the Diptera ; by 
others they have been considered to be most closely allied 
to the Coleoptera, but they are now generally treated as 
an independent order. 
The Euplexoptera or Earwigs are only too familiar to 
most of us. Linnzeus classed them among the Coleoptera, 
from which, however, they differ in their transformations. 
Fabricius, Olivier,and Latreille regarded them as Orthop- 
tera, but Dr. Leach, on account of the structure of their 
wings, considered them as forming the type of a distinct 
order, in which view he has been followed by Westwood, 
Kirby, and many other entomologists. 
The Thysanoptera, constituted of the Linnzan genus 
Thrips, minute insects well known to gardeners, differ 
from the Coleoptera in the nature of their metamorphoses, 
in which they resemble the Orthoptera and Hemiptera. 
The structure of the wings and mouthparts, however, are 
considered to exclude them from these two orders. 
The Trichoptera, or Caddis worms, offer many points 
of resemblance to the Neuroptera, while in others they 
approach more nearly to the Lepidoptera. According to 
Westwood, the genus Phryganea “forms the connecting 
link between the Neuroptera and Lepidoptera.” 
The last of these small aberrant orders is that of the 
Aphaniptera, constituted of the family Pulicide, In their 
transformations, as in many other respects, they closely 
resemble the Diptera. Strauss Durckheim indeed said 
that “da puce est un diptére sans ailes.” Westwood, how- 
ever, regards it as constituting a separate order. 
As indicated by the names of these orders, the structure 
of the wings affords extremely natural and convenient 
characters, by which the various groups may be distin- 
guished from one another. The mouth-parts also are 
very important ; and, regarded from this point of view, the 
Insecta may be divided into two series—the Mandibu- 
lata and Haustellata, or mandibulate and suctorial groups, 
_ between which, as I have already shown,* the Collem- 
bola (Podura, Smynthurus, &c.), occupy an intermediate 
position. These two series would stand as follows :— 
* Linnzan Journal, vol. xi. 
a - - 
a ee ee 
does ~~ ie (tare 
Pla ha ae ea 
April 10, 1873] NATURE 447 
I Ae 4 ae not otherwise acknowledged, have been Mandibulata Haustellata 
taken. e divides the insects into thirteen groups, with Hymenopter Lepi 
reference to eight of which it may be said that there is Strepsipteta 5 Deen sae 
little difference of opinion among entomologists. These Coleoptera Aphaniptera 
orders are by far the most numerous, and I have placed Euplexoptera Hemiptera 
them in capital letters. With reference to the other five Orthoptera Homoptera 
Trichoptera ? 
Thysanoptera ? 
Again, and this is the most important from my present 
point of view, insects have sometimes been divided into 
two other series, according to the nature of the metamor- 
phoses : Heteromorpha, to use the terminology of Prof. 
SFL 
LSS 7 
CZ} 
PLATE 3 
2, Meloe (after Shuckard), 
4, Sitaris (after Shuckard). 
7, Termes. 8, Stylops(female). 9, 
Pi, 3.—Fic. 1, Chloeon. 3, Calepteryx 
5 bey cn (after Gervais), 6, Acilius 
‘hrips. 
Westwood,* “or those in which there is no resemblance 
between the parent and the offspring and Homomorpha, or 
those in which the larva resembles the imago, except in 
the absence of wings. In the former the larva is gene- 
rally worm-like and articulated in its form, of a soft and 
fleshy consistence, and furnished with a mouth, and often 
with six short legs attached in pairs to the three segments 
* Introduction to the modern Classification of Insects, p. 17. 
