THE NOCTUINA. 127 
generally of moderate size; the hind wings are usually much 
folded under the fore wings, and the inner margins of the latter 
in repose frequently overlap. The caterpillar generally has 
sixteen legs, and, consequently, few loop when walking. Their 
chrysalis is usually found underground. The moths of the 
Quadrifide have generally broad wings, which sometimes are 
of very large size; the hind wings are but little folded, and the 
inner margins of the fore wings rarely overlap in repose. The 
caterpillars rarely have sixteen legs, and more frequently are 
noticed with fourteen or twelve, and many of them loop more 
or less when they walk. The chrysalis is rarely found under- 
ground. 
There are some Noctuina which particularly put one in mind of 
the Bombycina, and they are the Acronycta and the allied genera 
(forming the Bombycoide). A greyish-black caterpillar, with a 
broad yellow line down the back, having a large black hump on 
the fifth segment of its body, and a short black one on the twelfth, 
is very common during the autumn upon the elms, limes, and 
upon most fruit trees. When it has reached its full growth the 
insect descends from the branches and hides itself, either in the 
cracks in the bark of the trunk or in holes at the foot of the 
tree, where there is safe shelter, and then spins a light cocoon, 
and undergoes its metamorphosis. The chrysalis remains in its 
quiet condition until the month of June in the next year, when 
the metamorphosis into the moth takes place. The moth may 
be seen during the day-time upon trunks of trees, or upon 
walls, and may be recognised by a curious mark on the wing, 
which resembles a Greek letter. Hence the moth is called 
Acronycta pst. In England it is called the Common Dagger. 
Now, Acronycta tridens has a caterpillar which is orange red 
in colour, and which has a small black hump on the fifth, and 
a whitish black-crowned hump on the twelfth segment. This 
caterpillar differs, therefore, in its colour and humps from the 
common dagger caterpillar. But the moths of the two species 
resemble each other perfectly. The question arises at once in 
the mind, is this diversity of colouring and humping of very 
great importance, and of any specific value? It has been noticed 
in former pages that the caterpillars of succeeding broods of the 
