106 INSECTS INJURIOUS TO FOREST AND SHADE 'l'REES. 
are often destroyed by the maggots or larvee of two singular ichneumon 
flies (Rhyssa atrata and lunator). These are the largest known ichneu- 
mon flies; they are provided with long, slender borers or ovipositors from 
three to four inches in length, which they thrust into the deep holes 
made by the Tremex borers, in the bodies of which they insert an egg, 
(We have, however, observed one of these Rhyssw engaged in ovipos 
iting in an elm tree infested with the larvie of Compsidea tridentata. ) 
The following description of the larva is copied from our report ‘On 
the Insects affecting the Cranberry, with remarks on other injurious 
Insects.”* 
The larva.—A long, white, cylindrical worm, with the segment behind the head of 
the same width as the twelfth segment from the head; the thirteenth much narrower, 
regularly rounded behind, with a deep crease above, leading backward 
and a little downward to a small, sharp, terminal, dark-reddish horn. The 
horn is acute, with three teeth above, near the base, and two smaller ones 
on the under side. Each of the three last rings bulges out on the under 
side. The head is white, and about half as wide as the segment behind, 
into which it partially sinks. It is rounded, smooth, with the antennie 
represented by small rounded tubercles, ending in a minute horny spine; 
should the spine be regarded as indicating a joint, then the appendage is 
three-jointed. The clypeus is broader than the labrum by a distance equal 
to its own length. The labrum is a little more than twice as broad as long, 
with the front edge slightly sinuous. The large, powerful mandibles are 
four-toothed on one side and three-toothed on the other. The maxillx are 
three-lobed, the lobes unequal, ending in spines, the middle lobe with two 
spines, the outer lobe much smaller than the others. The labium or under 
Vic. 46.— lip is rather large, rounded, with a spine projecting on each side. The pro- 
Pane ie thorax or segment next behind the head is twice as long as the one behind 
columba, it, divided into two portions by asuture behind it. There are three pairs of 
oo8 abies small, soft, unjointed feet, of which the first pair are considerably the lar- 
Packard. oest; they do not project straight out but are pressed to the body and di- 
rected backward. There are ten pairs of spiracles, one pair on the hinder edge of the 
prothorax, twice as large as the others; the second pair between the second and third 
rings, and the eight others on the eight basal abdominal segments. Length, 2.25 
inches; greatest thickness, .28 inch. 
The larvee from which the above description was taken were found at 
Amherst, Mass., early in October, in a tree containing several of the 
adult insects, which had not left their holes and seemed likely to be 
destined to pass the winter in the tree. Clementi has in Ontario, Canada, 
taken several of the imago with the larvie from the oak in March, so 
that it undoubtedly hibernates as an imago. 
3. THE SIXTERN-LEGGED MAPLE-BORER. 
Dgeria acerni (Clemens). 
Order LErIpOPTERA; family AAGERIAD®. 
Following the work of the flat-headed borer, burrowing under the bark of the soft 
By F. V. Hayden, U.S. Geologist. Washington, 1878. 
