THE NATURAL HISTORY SURVEY. 25 
VI. INSTRUCTIONS FOR COLLECTING MOLLUSKS.* 
Before proceeding to discuss the particular species found 
within the limits of the area, it may not be out of place to briefly 
consider the methods of collecting and preserving specimens of 
this group.f Mollusks may be found in all parts of Illinois in 
almost every situation; in the woodlands, the swamps, the 
creeks and rivers and the lakes. Even the prairies have given 
us several species of this type. For convenience we will divide 
the group into two sections, viz.: 1. Land species. 2. Fresh- 
water species. 
I. LAND SPECIES. 
The land mollusks cover a variety of widely separated 
forms; some are with, others without shells; some are herbiv- 
orous and others are carnivorous. 
a. Hasirat.—Land mollusks exist under almost all condi- 
tions. In an old forest they will be found under dead leaves 
and decaying logs. The bark of old trees which is “starting,” 
and old, rotting stumps will be found prolific collecting sta- 
tions. The shelter of loose stones and boulders is also good 
ground for these animals. Other forms live on the leaves of 
sedges, grass and shrubbery. During the winter months these 
animals bury themselves in the soil at the base of these grasses 
and shrubs. A limestone region is the most conducive to the 
life and growth of land snails, and in this kind of a region they 
are very plentiful, while in a country composed of quartz (flint) 
they will not thrive and are seldom found. Where coniferous 
or resinous trees abound few if any mollusks will be found, 
while in a locality made up of deciduous or soft-wooded trees 
the snail fauna will be abundant and varied. Pungent herbs 
are inimical to snails, while the nettles are favorite localities 
for them. No pulmonate mollusk will live where sand, ashes 
or lime in a pure state are found. x 
The spring months are the best suited for the active life of 
snails, but it is not until midsummer that they reach their max- 
imum development. During the winter months they bury 
themselves in the ground, closing the aperture of the shell with 
a leathery secretion called an epiphragm; the naked slugs cover 
*For much of the information used in this topic the author is indebted to Dr. Wm. H. 
Dall’s ‘‘ Instructions for Collecting Mollusks, and Other Useful Hints for the Conchologist,"’ 
being part G of Bull. No. 39, U. S. National Museum, 
+The writer has inserted this topic for the reason that works upon this subject are not 
always to be obtained, and principally so that the reader of this report might have all the 
necessary information before him without consulting other works. 
