166 
THALESSA, 
OR 
RHYSSA SP. 
Plate VII, fig. 2. 
Reference :—Provisionally determined as above. 
Classification:—Order, HYMENOPTERA. Family, |lchneumonide. 
Parasitic upon SIREX sp. and perhaps upon XY PHIDRIIDES. 
Description. 
@?. A fair-sized insect. Head black. Eyes black with a 
longitudinal oval orange mark on either side almost surrounding 
them. Antenne long, filiform. Thorax black with yellow spots, 
wings membranous,* yellowish, with black veins. Legs long, 
black, except coxa which is yellow, and trochanta which is yel- 
low above and black beneath. Body black, shining, with a pink 
cerise spot on either side of each segment at the posterior edge. 
In dead dry specimensthese spots are either a dirty yellow 
or pale greenish blue. The coxz and trochantas are also 
blackish. 
Length t inch. Length of ovipositor 14 to 14 inches. 
(Seentley lignicyec.) 
| Life: History. 
This insect appears on the wingin June towards the begin- 
ning of the month, the time of emergence depending upon the 
elevation... I have only as yet found the perfect insect but under 
conditions such that I have no doubt that it is parasitic upon the 
Strex sp. I have found them together plentifully in spruce 
trees, the smaller exit holes of the ichneumon being mixed up 
with the larger ones of the sirex. (See Pl. VII, fig. 1, f. The 
smaller holes and upper section of a gallery are those of the 
Thalessa.) Numerous dead ichneumons were also found both in 
the wood anc bark, but under different conditions, Many of 
those in the wood were in borings which did not reach to the 
outside and were facing outwards, seeming to show that they 
had not been able to bore their way out, the larve which their 

