144 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



After the foregoing lines were written we fortunately observed a 

 female in confinement, June 29, while engaged in the process of oviposit- 

 ing; we should judge that the operation of sawing the slit and depositing 

 the egg required not less than five minutes, and perhaps not much more 

 than that length of time. The fly had been evidently at work for some 

 time previous, as a number of eggs had been laid along the shoot ; she 

 had begun at the farther end and worked down to the base of the new, 

 fresh , green shoot. She stood head downward while engaged in making 

 the puncture, and was not disturbed by our removing the larch twig 

 from the glass jar and holding it in our hand while watching the move- 

 ments of the ovipositor under a Tolles triplet. The two sets of serrated 

 blades of the ovipositor were thrust obliquely into the shoot by a saw- 

 ing movement ; the lower set of blades was most active, sliding in and 

 out alternately, the general motion being like that of a hand-saw. After 

 the incision is sufficiently deep, the egg evidently passes through the 

 inner blades of the ovipositor, forced out of the oviduct by an evident 

 expulsive movement of the muscles at the base of the ovipositor. The 

 slit or opening of the incision after the egg has passed into it is quite 

 narrow and about If mm in length. While engaged in the process the 

 antennae are motionless, but immediately after the ovipositor is with- 

 drawn they begin to vibrate actively, the insect being then in search of 

 a site for a fresh incision. 



After making the foregoing observations we found at Phillips, Me., 

 July 1, and at Errol, N. H., July 4, numerous twigs containing eggs, and 

 the flies were also o.bserved upon the trees ovipositing. Although the 

 slit is at first closed, as soon as the embryo increases in size the twigs 

 swell where they have been incised by the ovipositor, and the slits en- 

 large and gape more or less, becoming much larger and more conspicuous 

 than when the eggs are first deposited. It would thus appear that 

 oviposition takes place about a week later in the vicinity of Brunswick. 

 Me., than in Essex County, Massachusetts, and about a week later in 

 Northern Maine and New Hampshire than on the coast at Brunswick. 



When the larva hatches, the incision gapes open, leaving an oval hole. 

 Out of this gape the larva creeps, and it rarely eats the terminal shoot, 

 but crawls upon the leaves of the whorls next to the terminal shoot. 

 At first it nibbles one side of the needle or leaf, leaving it half eaten 

 and rough, serrate, and partly withered along the edge. The half- 

 eaten, withered leaves of unequal length in a whorl on the ends of the 

 smaller branches enable one to detect the presence of the young worms 

 on the tree. 



Usually after the young larvaB have shed their first skin, they collect 

 on the verticils of the larch and almost invariably begin to eat the 

 needles, one after another, beginning at the distal end and eating the 

 leaf obliquely until only a short stump is left; in this way one verticil 

 after another is eaten, and when the worms are half-grown they occa- 

 sionally collect around the main stem of the twig in singular clumps or 

 clusters, the hinder part of the body curled over their backs, and, owing 

 to their oblique posture in reference to one another, appearing like a 

 ball of worms. This singular appearance was briefly noticed by Katze- 

 burg. The castings or excrement are long, cylindrical, more or less 

 truncated at each end. Our saw-fly differs slightly, as has been de- 

 scribed, from the German in the eggs being laid at the base of the leaves 

 on the newly-grown shoots, rather than on or just under the epidermis 

 of the last year's shoots, where we have repeatedly and in vain searched 

 for them. The larvae were observed to hatch out from June 20 to 30 at 

 Brunswick, Me. 



