214 ENTOMOLOGY 
far more variable than others. Catocala tha, for example, 
occurs under more than fifty varieties, each of which might 
be given a distinctive name, were it not for the fact that these 
varieties run into one another. One may examine hundreds 
of potato beetles (L. decemlineata) without finding any two 
that have precisely the same pattern on the pronotum. The 
range of this variation in this species is partially indicated in 
Fig. 237, and that of Cicindela in Fig. 238. 
Individuals of Cicindela vary in pattern in a few definite 
directions, and the patterns that characterize the various spe- 
cies appear to be fixations of individual variations. In the 
words of Dr. Horn: 
ee 
(1) The type of marking is the same 
in all our species. (2) Assuming a well-marked species (vul- 
garis, Fig. 238, ©) as a central type, the markings of other 
species vary from that type, (a) by a progressive spreading 
of the white, (b) by a gradual thinning or absorption of the 
white, (c) by a fragmentation of the markings, (d) by linear 
supplementary extension. (3) Many species are practically 
invariable (7. ¢., the individual variations are small in amount 
as compared with those in other species). ‘These fall into two 
series: (a) those of the normal type, as vulgaris, lurticollis 
and tenuisignata; (b) those in which some modification of the 
type has become permanent, probably through isolation, as 
marginipennis, togata and lemmiscata. (4) Those species 
which vary do so in one direction only.’’ New types of pat- 
tern, of specific value, appear to have arisen by the isolation 
and perpetuation of individual variations. 
Variations in general fall into two classes: continuous (in- 
dividual variations) and discontinuous (sports). The former 
are always present, are slight in extent and intergrade with 
one another; they are distributed symmetrically about a mean 
condition. ‘The latter are occasional, of considerable extent 
and sharply separated from the normal condition. 
Replacements.—Examples of the replacement of one color 
by another are familiar to all collectors. The red of ’anessa 
atalanta and Coccinellidee may be replaced by yellow. These 
