26 
Psyche 
[March 
I take it that no one will deny that the number of species 
in an order is an index to the “health” of that group. At 
least it is obvious that such an aggregation as the Coleop- 
tera, with close to 200,000 existing species, is in less dan- 
ger of becoming extinct within the next thousand years 
than, say, the Mecoptera, of which less than 200 species 
have been found in all regions of the earth. Consequently, 
an accurate idea of the “species strength” of the orders can 
be obtained by determining the percentage of species which 
each order contributes to the entire insect fauna. The pres- 
ent percentages for some of the existing orders are shown 
in the right-hand column of figure 2. Here we see that the 
Mecoptera, Neuroptera, Odonata, Psocoptera, Plectoptera, 
and Blattaria each make up less than 1% of the known 
species. The Orthoptera and Homoptera are but little bet- 
ter, with about 3% and 3.5% respectively. The Coleoptera 
lead with the striking figure of 41%. 
TABLE NO. 2. 
RELATIVE ABUNDANCE OF SPECIES IN EACH ORDER 
AT DIFFERENT PERIODS 
(Figures in Percentages) 
Mecoptera 
Permian 
9.0 
Mesozoic 
3.7 
Tertiary 
.16 
Recent 
.035 
Neuroptera 
3.0 
4.8 
.50 
.42 
Odonata 
80 
6.6 1.6 
.56 
Homoptera 
12.5 
9.0 
4.0 
3.4 
Psocoptera 
6.0 
.25 
.45 
.12 
Coleoptera 
1.0 
37.0 
37.0 
41.5 
Plectoptera 
3.5 
2.0 
.30 
.095 
Diptera 
30 
5.0 
27.0 
10.8 
Orthoptera 
30 
9.0 1.2 
2.9 
Blattaria 
34.0 
7.0 
.90 
.42 
Even a casual examination of the geological history of 
the insects will indicate that quite different conditions have 
prevailed. In the case of the Mecoptera, for instance: 10 
species of these insects have been secured in the Lower 
Permian of Kansas, 4 species in the Russian Permian, and 
15 in the Australian Permian, making a total of 29 species 
from these three deposits. Yet in the Tertiary, which has 
produced more than twenty times as many species of fossil 
insects as the Permian, we have found only a total of 12 
