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acters, it is usually the male which is the more advanced or 
complex, apart from such special structures which serve the 
welfare of the offspring, as for instance the anal wool of many 
female moths and the long rostrum of some female weevils. 
We are so accustomed to find that it is the male which has a 
stridulating organ, or a scent-organ, or more strongly pecti- 
nated antennae, etc., that exceptions come as a surprise. 
In the literature on organic evolution, that which is usual is 
frequently taken as expressing a general law. The exceptions, 
however, prove that we have to deal with adaptations which 
appear again and again only as long as circumstances require 
or permit it. Like the human laws, the direction which 
evolution takes depends on internal and external factors and 
is not fixed as is often maintained ( Orthogenesis’’). In 
this connection the exceptions from the usual are of great 
interest. The African Saturniids exhibited may serve as an 
illustration. The females of Holocera and Ludia have a kind 
of stridulating organ which is absent from the males. The 
underside of the fore-wing bears before the tornus a large 
area of peculiarly modified scales, which are so twisted that 
their surfaces are more or less vertical on the wing, the scales 
presenting the anterior and apical edges to the observer. 
On the hind-wing the corresponding portion of the costal 
margin is incrassate and bears a variable number of spikes, 
which stand upright and scrape on the fore-wing when the 
wings are in motion. Although entomologists who have 
handled live specimens do not seem ever to have heard the 
moth produce a sound, the apparatus has the appearance of 
a stridulating organ. The sound may be imperceptible to 
the human ear. 
Dr. K. Jordan further exhibited two species of Graphipterus 
from Algeria and demonstrated the stridulating organ which 
Pocock has described in Ann. Mag. N. H. (7), x, p. 154 (1902). 
G. rotundatus Klug (1830) is common in the sandy desert 
and frequents the hillocks of loose sand crowned by bushes 
of Limoniastrum or Tamarix. On the Central Plateau of 
Algeria, at Guelt-es-Stel, we found a small-spotted form, 
G. peletieri Casteln. (1847), in association with Cicindela 
truquii Guér. (1855). The resemblance between the Cicindela 
