THE SUBSTITUTE. 
237 
not, at least generally, double- 
brooded. (Vol. I., pp. 338, 339.) 
Trachea. 
The extreme shortness of the 
palpi, the head small and con- 
cealed, the woolly clothing of the 
thorax and abdomen, the legs, &c., 
approximate this genus to the 
Bomhyces, with which Fabricius 
had placed it; but the tongue, 
though short, is very distinct, the 
position of the wings in repose is 
quite that of the Noctuce, as is 
^so the neuration, and the larva 
and chrysalis leave us no room to 
doubt. 
The larva of the only species of 
Trachea has quite the appearance 
of our Orthosia, and the lines are" 
more sharply marked than any 
other ; it feeds in great nnmbers 
on fir trees, especially on Pinus 
sylvestris, which it sometimes 
completely devastates, but, as it 
always remains quite exposed on 
the leaves, which are uot large 
enough to cover it, it is open to 
many risks of destruction, so that 
M. Treilschke says “ hardly one 
per cent, escapes,” but this does 
not prevent it from causing great 
ravajres in some forests. (Vol. I., 
p. 339.) 
Tceniocampa. 
The Tceniocampa are recognised 
at a glance by their hairy body ; 
the wings being powdery, and as 
it were mealy ; the palpi and 
tongue short, &c. They have a 
very Bombyciforin appearance, and 
if we add that the majority of the 
species have pectinated antenme, 
we shall hardly be surprised that 
ancient authors, deceived by tiie.se 
external characters, had classed 
them almost all with the Bom- 
byces. 
The larvae are hardly less re- 
cognisable ; the neatness of their 
lines, their body long, velvety, 
most frequently adorned with gay 
colours, or agreeably variegated, 
often cause them to be marked ; 
the greater part of them are com- 
mon, and it is not often that we 
beat a dozen trees without causing 
several of them to fall. Hence 
they would become, destructive to 
our oaks, elms and poplars, on 
which they feed by preference, if 
Nature had not imposed a parti- 
cular obstacle to their multiplica- 
tion ; this obstacle is the facility 
with which their chrysalides dry 
up, which only allows about a 
third of those which assume the 
chrysalis form to arrive at a per- 
fect stale. What is very remark- 
able is, that this drying up takes 
place when the insect is almost 
ready to .appear, so that we find 
the perfect insect entirely formed 
in these abortive chrysalides. If 
we add to this precaution of Na- 
ture, the ordinary accidents to 
which all larvae feeding exposed 
are liable, birds, Carabidfe, ich- 
neumons, flies, which do not spare 
these any more than other species, 
we shall understand why it is that 
Nocluce, so widely diffused and of 
which the eggs are hatched at so 
propitious a season, do not become 
a pest. Independently of all these 
enemies, some larvae of Tcenio- 
campa have even another enemy 
in individuals of their own species. 
In fact those oi cruda and miniona 
are cannibals, and when shut 
up one with another, or with other 
cater])illars, they attack and de- 
vour them with the ferocity which 
soon finds its punishment in a 
