INSECTS AND OTHER ANIMAL Pests I[NsguRIOoUS TO FIELD BEANS 987 
Method of feeding 
Agriolimax agrestis does not eat in the same manner as does a biting 
insect, for its feeding apparatus is very different. The jaw (Plate LXIX, 
10) is a concave, chitinous process attached to the roof of the pharynx. 
In the center it bears a tooth with finely serrate edges, which helps in 
tearing food apart. Opposed to this, on the floor of the pharynx, is a 
flexible plate made up of many small, sharp teeth, known as the radula 
(Plate LXX, 1, and fig. 92, A, page 981). This radula, or lingual ribbon 
as it is sometimes called, is supported on the muscular tongue and may 
be moved forward and backward. By the combined use of jaw and 
radula, small particles of food are torn from a plant and are then passed 
on to the stomach. Cooke (1895) states that the teeth of the radula are 
sharp enough to break the skin of the human hand if the slug is permitted 
to use this organ for a short time in one place. 
Mating and oviposition 
It has been previously noted that Agriolimax agrestis is hermaphroditic, 
both male and female sexual organs being found in the same individual. 
Whether or not the slugs are capable of self-fertilization is not definitely 
known. Theobald (1905) says that self-fertilization is rare, and that 
the male and female reproductive organs mature at different times. In 
the winter of 1917-18 the writer isolated specimens of agrestis a few days 
old and kept them in breeding jars in the insectary. One slug, on reaching 
maturity, deposited a few eggs; but because of an accident to the heating 
plant at a time when the temperature was far below zero, these eggs were 
frozen. Since that time it has been impossible to obtain eggs from isolated 
Beene, and therefore it cannot be said whether eggs of this type are 
fertile. 
On the evening of July 7, 1920, the writer saw for the first time the 
sexual union of A. agrestis. Two specimens, one much larger than the 
other, were crawling around and around each other on a patch of slime 
about an inch in diameter. Sometimes they would strike each other 
with their tentacles. Soon the excitatory organ, or sarcobelum, was 
extruded, and this also was used in a caressing manner. After this be- 
havior had continued for about three-quarters of an hour, the sarcobelum 
of each slug enlarged very greatly; the two organs came together and there 
was a great discharge of slime. In regard to the actual transfer, Taylor 
(1907:107) says, ‘‘ The seminal element, mixed with mucus and worked 
up into a little ball, is transferred bodily, the forerunner of a true sper- 
matophore.”’ 
Time required to reach maturity 
In ordinary years, under field conditions in New York, slugs that have 
developed from eggs hatching in May are ready for oviposition in October 
