386 
ANNUAL REPORT OF NEW-YORK 
CHERRY. LEAVES. 
94. Black-cai,fed saw-fi.y, Nematus suratus,new species. (Ilymenoptera. 
Tcnthrcdinid®.) 
This comes from a cocoon 0.30 in lengtn by 0.14 in diameter. 
The fly eats off the end of its cocoon to make its exit therefrom. 
It was met with at the same time with the preceding species, and 
was a week later in hatching. The fly is black with four trans¬ 
parent slightly smoky wings, its mouth lurid white as is also a 
cloud-like spot on the shoulders, the edges of the abdominal seg¬ 
ments, and the legs, the four anterior thighs being black upon 
their under sides and the hind pair wholly black except at their 
bases. Length 0.25, to the tip of the wings 0.30. 
A surprising degree of intelligence was manifested by this 
insect, in the situation which it selected for its cocoon. Upon a 
small limb growing perpendicularly upward the moth of an apple 
tree caterpillar had placed its belt of eggs, coated over with gum 
in the usual manner, and immediately above this a small tender 
leaf was growing. The worm spun its cocoon between this belt 
of eggs and the leaf above it. The frosts of autumn subsequently 
wilted this leaf and the rains saturating it weighed it downward, 
causing it to adhere like a wet cloth to the belt of eggs, the gum 
upon which afterwards drying glued the leaf securely in this 
position. And thus the stem of the leaf came to form a band or 
loop over the cocoon, holding it securely in its place. It is truly 
wonderful how the worm which formed this little thimble-like 
cocoon could have known that this spot was so well adapted for 
its wants. Had it previously crawled over these caterpillar’s eggs 
when they were wet, and thus discovered that their gummy cover¬ 
ing then became soft and adhesive I And had it the intelligence 
to foresee that the leaf growing immediately above them would 
in a short time wither and lop downwards and become firmly 
glued to the surface of this gum 1 It would so appear, from the 
fact of its placing its cocoon crosswise of the twig, so that it might 
become bound to it in this manner, instead of attaching it length¬ 
wise as insects generally place their cocoons, and from the further 
fact that it imbedded the lower end of the leaf stalk in the outer 
surface of its cocoon, evidently for the purpose of holding the 
leaf steadily in such a position that when it wilted it must lop 
