386 ANNUAL REPORT OF NEW-YORK 



CHERRY. LEAVES. 



94. Black-calfed SAW-FLY, ^ematus swraf us, new species. (Ilymenoptera. 

 Tenthredinidae.) 



This comes from a cocoon 0.30 in lengtn by 0.14 in diameter. 

 The Hy 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 

 ©f 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 1 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 ? 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 



