1930 ] 
Orders of Insects 
161 
Mouth and Metamorphosis.. McLachlan 1881-1926 
Froggatt 1908 
Lafroy and Howlett 1909 
Mouth, Metamorphosis, Thorax and Dominance 
Sharp 1895-1923 
Metamorphosis Osborn 1908-1917 
A conception of high and low development that came 
with the theory of evolution has had the most profound 
influence on classification as seen by the fact that only 
one of the pre-Darwinian arrangements began with the 
Orthoptera and this order formed one end of the series 
in every system but one that has been proposed since that 
period. Entomologists are practically unanimous in plac- 
ing the Orthoptera lowest, but there is no agreement as to 
which order is highest, six selecting Hymenoptera, four 
favor Lepidoptera, the same number Diptera, two Hemip- 
tera, and one Coleoptera. There is a fair degree of agree- 
ment regarding which order stands next to Orthoptera, 
twelve selecting Hemiptera, four Coleoptera, and one 
Hymenoptera, these latter five being those still clinging to 
the Fabrician division based on the mouthparts, while the 
majority favor the division based on metamorphosis fol- 
lowing Oken. 
There is an agreement among all recent students of phy- 
logeny that each of the six major orders have been derived 
independently from lower forms, and difference of opinion 
as to the affinities and arrangement of these hypothetical 
ancestors explain in large part the diversity of arrange- 
ment. 
The writer has suggested that a chronological arrange- 
ment be followed, since now for a good many years our 
knowledge of the fossils is adequate to permit of this 
arrangement. This does not apply to the minor orders in 
which the palaeontological evidence may never be adequate. 
Handlirsch, who has given very great attention to the fossil 
insects, has clung to the arrangement of Fabricius, which 
has required the shifting of the Diptera and Hemiptera 
beyond the Lepidoptera. Had he set these where they 
