988 I. M. Haw.ey 
of the same year. This makes the time to sexual maturity about five 
months. In the wet season of 1917 this period was shortened to three 
months for some individuals. When the slug overwinters, it may be 
more than twelve months before it begins to deposit eggs. 
Many specimens of Agriolimax agrestis that. hatch in the spring do 
not live thru the following winter under New York conditions. In no 
case have slugs under observation lived thru two winters. This would 
make the greatest length of life actually observed in New York about 
eighteen to twenty months. 
In European writings it 1s stated that A. agrestis may live for several 
years (Theobald, 1895); also, that the slugs are sexually mature in six 
weeks, and that there may be several generations in a year (Reh, 1913). 
Cooke (1895) reports that slugs of this species are usually full-grown by 
the middle of the second year and die during the first part of the third 
year. Taylor (1907) cites one instance in which a slug mated and deposited 
eggs In sixty-six days, was full-grown in eighty-two days, and lived for 
about eighteen months. The same writer states that the time from 
hatching to maturity probably varies from ninety days to nearly one 
year. 
NATURE OF OUTBREAKS 
When the outbreaks of Agriolimax agrestis occurred in 1917, it was 
noted that ordinarily the bean fields were evenly attacked. All the plants 
showed some injury to leaves and vines, but only a few were completely 
destroyed. The exception to this was in a field where a large tree, with 
its border of sod, seemed to act as. a center from which the slugs migrated. 
In the grass near this tree were found many eggs and adults of A. agrestis, 
showing the place to be the local seat of infestation. 
Only one outbreak of agrestis was observed by the writer in New York 
in 1918, and that was in Monroe County, in a slightly rolling field where 
the knolls had been covered with horse manure in the preceding fall. 
This field had been in sod for several years. The infestations seemed to 
start from the knolls, and when the field was seen by the writer the plants 
had been entirely destroyed as far as the slugs had migrated (fig. 92, C, 
page 981). Leaves and vines were completely devoured and the parts below 
ground were also attacked. The infested area grew larger each night 
as the slugs moved forward along the rows. In this infestation slugs of 
all sizes were present; the larger ones (40 millimeters) were in the front 
ranks of the advancing hosts, while far back in the devastated part of the 
field were the small ones (4 millimeters), which had been left behind in 
the rapid advance. This variation in size is unusual in New York and 
was probably the result of the exceptionally good hibernating place pro- 
vided by the manure and sod of the field, which no doubt had allowed 
more or less continuous development thruout the winter. 
