SUMMARY OF HABITS AND CHARACTERISTICS. 13 
of this peculiarity, assuming it to be abnormal, we can at least see 
certain advantages coming to the species therefrom. Among these 
are the protection from attacks of parasitic enemies, since we can 
hardly conceive of a parasite limited to this Cicada which could pos- 
sibly extend its existence over an equal term of years. Its occur- 
rence, also, in overwhelming numbers at almost the same moment 
everywhere within the range of the brood prevents its being very 
often seriously checked in its adult stage by the attacks of birds 
and other vertebrate enemies, which fatten on it in enormous num- 
bers. For this species this is a most important consideration, for it is 
naturally sluggish and helpless and seems to lack almost completely 
the instinct of fear common to most other insects, and this leaves it 
an easy prey to insectivorous animals. The almost entire absence of 
fear and consequent effort to save itself from danger by flight or 
concealment is apparently a consequence of the long intervals between 
its aerial appearances. 
The greatest check on the species has been in the advent of Euro- 
peans on this continent and the accompanying clearing of woodlands 
and increase of settlement. The vast areas in the more densely popu- 
lated East, which were once thickly inhabited by one or the other of 
the broods of the periodical Cicada, are rapidly losing this character- 
istic, and the Cicada will doubtless appear in fewer and fewer numbers 
in all settled districts. A recent important factor which is assisting 
in this particular is the English sparrow, and it has been shown by 
Professor Riley and later observers that in and about cities nearly all 
of the few cicadas which still emerge under these more or less unfavor- 
able conditions are devoured by this voracious bird. On the other 
hand, as stated (p. 58), the first brood of these insects to be noted 
by the early New England colonists, namely, the swarm recorded for 
Plymouth for 1634, was just as abundant in 1906, the year when it 
last recurred, as ever. This is, however, not the normal condition, 
the wooded areas having been considerably maintained in Plymouth 
and Barnstable counties, whereas ordinarily such wooded areas have 
been greatly reduced or obliterated, and the Cicada in consequence 
slowly exterminated. 
The rapid disappearance of the Cicada, as a result of the clearing of 
forest areas and the conditions which accompany settlement, is nota- 
bly shown in the case of Brood XI, which formerly occupied a compact 
territory in the valley of the Connecticut River in the States of Massa- 
chusetts and Connecticut. In a letter to the writer, Mr. George 
Dimmock, who has made a special study of this brood in the northern 
part of the town of Suffield, Conn., says: ‘‘ When I saw them in 1869 
the cicadas were so abundant that small bushes and undergrowth in 
the rather sparse woods in which they occurred were weighted down 
with them.” In 1886 he was unable to visit the region, but was 
