20 THE PERIODICAL CICADA, 
Smith came from Indiana and the rest from Michigan. Too muecn 
importance, however, can not be given to this isolated experience. 
Correspondence was kept up with as many of the points as could be 
reached during the next four years, but no further records were 
obtainable. 
Nothing whatever came of the 13-year material sent to northern 
localities. 
The difficulty in an experiment of this kind lies in the long term 
over which it extends, and the inevitable changes of local conditions 
and the removal or death of observers intrusted with the experiment. 
It is necessary, as demonstrated by a later test (see pp. 114-116) of 
egg transfers, to have an enormous quantity of eggs to insure the insects 
going through the entire term undestroyed by natural enemies or 
accidents. 
THE DWARF PERIODICAL CICADA. 
In connection with the discussion of the 13-year and 17-year races of 
the Cicada, it 1s interesting to note also that in both races the insect 
occurs in two distinct types, viz, a large form and a small form, 
the former comprising the bulk of the individuals of the brood and 
the latter more rare and often unobserved. The existence of these 
two types was commented upon as early as 1830 by Doctor Hildreth, 
of Marietta, Ohio,“ and was especially remarked in the great Cicada 
year 1868. The typical larger Cicada (fig. 1, A) measures on an 
average 14 inches from the head to the tip of the closed wings and 
expands over 3 inches. The underside of the abdomen is of a dull 
orange-brown color and in the male four or five segments are of the 
same color on the back. The smaller form is rarely more than two- 
thirds the size of the larger, and usually lacks altogether the light 
abdominal markings, although they are sometimes represented on 
the edge of the segments beneath. 
The small form (fig. 1, B) was described in 1851 as a distinct species, 
Cicada cassinii, by Dr. J. C. Fisher.’ The contention that it repre- 
sents a distinct species was urged particularly on the ground that there 
exists a variation in the genitalia, but this variation has since been 
shown by Professor Riley not to be constant, and specimens are to be 
found in both sizes which present the same structure in these parts. 
In view of the close anatomical correspondence, except in size, of 
the two forms and the fact that they always occur together in the same 
broods and have the same anomalous subterranean period of larval 
and pupal life, the specific importance of the smaller Cicada has been 
naturally open to question, and in Bulletin 14 the writer was inclined 
a Silliman’s Journal, XVIII, p. 47. 
b Proc. Acad. Nat. Sc. Phila., Vol. V., p. 272. 
