June, 1919 Bulletin of the Brooklyn Entomological Society 93 
interstitial area varies in areolar count only in brachypterous 
specimens ; the analogue of this area in macropterous specimens, 
has invariably a single row of areoles on each side of the claval 
suture ; the count of areoles for the sutural area of macropterous 
specimens refers to the series of areoles in reticulated area be- 
tween posterior extension of brachial vein and membrane. 
REMARKS ON THE ORIGIN AND SIGNIFICANCE OF 
METAMORPHOSIS AMONG INSECTS, 
By Gi €. Crameron, Pep: 
(Continued from p. 40.) 
In several publications (notably in his book “ Die fossilen In- 
sekten”), Handlirsch has developed the idea that cold is the 
initiating factor in the production of holometabolism. One of 
the reason he proposes for so thinking is that under present cli- 
matic conditions, insects with incomplete metamorphosis flourish 
in mild, frost-free and tropical regions; while he seeks to give 
the impression that insects with complete metamorphosis occur 
largely in cold climates. Orthoptera, Phasmide, Mantide and 
Embiide are wholly absent from the arctic regions, while a large 
number of Lepidoptera, Diptera and Hymenoptera, etc., occur in 
the cold climates. Of such insects with incomplete meta- 
morphosis as occur in climates with cold winters, most are not 
peculiar to those climates, but occur in warm climates as well, 
and have gradually adapted themselves to the colder climates as 
migrants from the warmer zones. On the other hand, many 
species of holometabolous insects are peculiar to the colder 
climates in which they occur. He points out that of all known 
species of Dermaptera, only about 4 per cent. occur in temperate 
regions with well marked winters, 2 per cent. of the Blattide, 
and a much smaller percentage of the Mantide, Phasmide, etc. 
On the other hand, about 30 per cent. of the species of Coleop- 
tera, 40 per cent. of the Hymenoptera and 50 per cent. of the 
Diptera occur in temperate regions. In the Carboniferous 
