¹ Townsend erroneously described the egg of this species (Manual of Myiology, pt. IV, p. 241) as having the chlorion absolutely plain. It is true that the sculpture is rather inconspicuous.

² An interesting problem in connection with ovoviviparous Tachinids is the internal determinism of oviposition, stimulated externally by the perception of the host, at least in most cases. Generally speaking the eggs should contain larvae ready to emerge at the time they are deposited, otherwise the eggs of forms such as blanda would be eaten and excreted while still undeveloped. In experiments on Blepharipoda scutellata R.-D. the writer found that unfertilized females having the uterus full of sterile unpigmented eggs will deposit them on leaves. This suggests that the stimulus may be mechanical and depends on uterine distension. But in that case the rate of devlopment must be such that when the last eggs necessary to distend the uterus are descending from the ovarioles, the first eggs must normally contain fully formed larvae, ready to emerge. In fact however, as stated above, some species such as Euexorista futilis O.S. may have the uterus distended with pigmented eggs which are still undeveloped, even at the lower end. The mechanism involved is not easy to conceive.

³ The egg of fimbriata in my material, is thin and only faintly pigmented, though it contains a fully developed larvae; in this respect also, it resembles E. blanda.