THE SUBSTITUTE. 
33 
in the localities (always rather re- 
stricted) where they occur. 
The species of the family Leu- 
canidcB are very numerous ; and as 
their markings are often 7iil, the 
differences which separate them 
are often insignificant. Hence, 
they are very difficult to study. 
This study is, besides, rather un- 
satisfactory, because it relates to 
the least ornamental as well as to 
the least varied of all the Noctute. 
However, we do not see that 
authors have neglected this group 
more than others, and there are 
even entomologists who have a 
sort of predilection for it, which is 
explained by the pleasure we de- 
rive from overcoming difficulties. 
(Vol. I., pp. 6o, 6fi.) 
Leucania. 
The larvte of Lexicania are very 
closely allied to each other, and 
one needs all the experience that 
one can acquire from long practice 
in breeding larvae in order to dis- 
tinguish them ; even the most 
skilful is often deceived. Not a 
single European species, to my 
knowledge, is green : all are of a 
dull whitish, or of a reddish or 
yellowish gray, with the ordinary 
lines continuous and well marked, 
and between these lines a number 
of other lines, or supernumerary 
lines, often resulting from the 
agglomeration of brown or reddish 
atoms. These are nearly all the 
markings, though sometimes the 
subdorsal line is marked with 
black spots ; the spiracles are often 
entirely black or brown. These 
larva) feed exclusively on grasses, 
and we find them on those which 
grow with their roots almost in 
the water, and on those growing 
on the most arid hills. Those 
grasses which form thick tufts 
afford a natural shelter, in the 
midst of which the larvae pass 
their lives, only climbing to the 
extremity of the leaves in the 
evening or at night. Those which 
do not feed on grass growing in 
tufts have to seek a shelter among 
dried leaves. Some of those which 
feed upon aquatic grasses take 
shelter in those stems of which the 
top has been cut off or accidentally 
broken. They penetrate till their 
progress is stopped by a knot, and 
their excrements, which fill a por- 
tion of these tubes, testify that 
they only quit these hiding-places 
when obliged to seek food. This 
retreat, if it does not protect them 
from prying Ichneumons, com- 
pletely shelters them from the 
attacks of birds ; but that is not 
its only benefit : they make use of 
it when the period arrives for their 
metamorphosis. In fact, they do 
not enter the earth like their con- 
geners, and they content them- 
selves with spinning above and 
below them a silken diaphragm 
mingled with gnawings of reed. 
(Vol. I., p. 70.) 
Nonagria. 
This is a genus much more re- 
markable for the habits of the 
larvae than for those of the perfect 
insects, although these latter are 
well deserving of attentive study. 
These larvae spend their whole 
life, from the time they quit the 
egg till the perfect insect ap- 
pears, in the interior of stems of 
aquatic plants, eating the pith 
and never touching the leaves. 
The small larvre, when quitting 
the egg, generally live in compa- 
nies on one stem, and at the top 
where the part to be perforated is 
