Callirhytis pigra, n. sp.
The galls of this species answer perfectly to Baron Osten-Sacken's description of C. q. tumifica. They are large irregular swellings on the midrib of the leaves of Q. tinctoria [velutina], always on the under side and usually on the lower half of the leaf. Sometimes two distinct galls are found on the same leaf. Their presence is only indicated on the upper surface by a widening of the midrib and a slight depression of the leaf at that point. They are often an inch in length and in the middle half an inch in diameter, tapering more or less towards the ends. They are of a dense cellular tissue, with the woody fibre of the midrib along the axis. The cellular portion contains a large number of larval cells, which are inseparable from the enveloping substance. Having discovered a young oak nearly all of whose leaves had these galls upon them early in June last year, I made frequent visits to it to watch the development of the larvae. Quite sure that they would prove to be Cynips q. tumifica, I expected to find the insects fully matured early in July, but at that time the larvae could scarcely be seen in the soft, immature vegetable cells that surrounded them, and it was late in autumn when the perfect insects made their appearance. This extremely slow development suggested the specific name. The gall flies are all females, and differ widely from C. q. tumifica O S.”
- HF Bassett: (1881) New Species of Cynipidae©