576 
The northward migration seems to have been 
quite general. They made their first appear- 
ance in the vicinity of Kansas City early in 
September, and by September 26-30 were 
present in countless swarms at Kansas City 
and Holden. They reached Macon in north 
Missouri September 24, and were very abun- 
dant and troublesome until frost. Here at 
Columbia they were especially abundant the 
last two weeks of September and early Oc- 
tober; while later in October the moth of the 
army worm (Leucania unipunctata) was far 
more abundant, collecting about cider mills 
and injured and decaying fruit. With condi- 
tions favorable next year, we may expect con- 
siderable injury from the army worm in this 
state. 
One point with reference to the moth of the 
cotton worm which the other notes have not 
brought out, is the injury which they do to 
ripening fruit in the orchard and where fruit 
is exposed in the market. This has been espe- 
cially emphasized in all the letters received at 
this office this fall. As is well known, this 
moth has rudimentary mandibles by means of 
which it can break the skin of fruit and then 
with its proboscis it sucks out the juices. 
Late peaches, especially Heath Clings, are re- 
ported as having been severely injured this 
year. In some cases a dozen or more at a 
time collect on a single peach and eventually 
all the juice is consumed, leaving only the 
skin, pulp and pit. Grapes and even bananas 
in the market are attacked. In the orchard, 
after the peaches were picked, the moths 
turned to the apples. Their attack on the 
apple is similar to that on the peach except 
that the juice is drawn out in patches which 
turn brown and become mellow like bruises. 
The affected patches vary from the size of a 
pea to that of a dime or a quarter. The most 
of the fruit so attacked decays. 
The strange northward migration of this 
moth which has always been of considerable 
interest to the entomologist has proved to be 
of special interest to many of the Missouri 
fruit growers this year. 
LronarD HasEMAN 
DEPARTMENT OF ENTOMOLOGY, 
UNIVERSITY OF MISSOURI 
SCIENCE 
[N.S. Vou. XXXV. No. 902 
CRYSTALLOGRAPHIC TABLES 
To THE Eprror oF Science: As a teacher of 
crystallography I have found that students 
rarely appreciate the full significance of the 
fundamental laws of the science until, by 
actual measurement and calculation, they have 
found concrete evidence. With large crystals 
of quartz, calcite, tourmaline, zircon, rutile, 
barite, staurolite and a number of others, 
satisfactory results may be obtained by use of 
the Penfield hand goniometer. The advantage 
of such crystal measurement is twofold; it il- 
lustrates the laws which govern the arrange- 
ment of crystal planes, and it teaches the 
value of the science as a means of mineral de- 
termination. 
Regarding the latter phase of the study, stu- 
dents are taught the methods of measurement 
and calculation necessary in each system for 
the determination of axial ratios. To bring 
out clearly the real value of such calculations 
as a means of practical mineral determination 
some sort of reference table of axial ratios 
seems desirable. Such tables have been com- 
piled in a somewhat imperfect form, and it is 
to these that attention is directed. 
The axial ratios of common tetragonal and 
hexagonal minerals are arranged in ascend- 
ing values of c, the mineral names being 
placed in a parallel column. In practise the 
chart is placed before a class with the mineral 
mames covered. After careful measurement 
and calculation the student refers to the 
column of ratios, and the fact that he can, in 
many cases, determine the mineral properly 
by this means alone, makes it a most illumi- 
nating and interesting exercise. 
The orthorhombic system presents consid- 
erable difficulty in compiling a table of ratios 
since there are three possible ways in which 
the values of a, b and c may be arranged and 
still be in accord with the convention that b 
must be greater than a. Having determined 
the axial ratios, one is in doubt as to the 
proper arrangement. The three possible 
values of a, which may occur, b being unity, 
are the value of a when (1) c is greater than 
a and also greater than b; (2) c is greater 
than a and less than 6; (8) ¢ is less than a 
