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The Tachinid Parasites of Archips cerasivorana Fitch. (2) Eusisyropa blanda O. S. (Diptera)

Published online by Cambridge University Press:  31 May 2012

W. R. Thompson
W. R. Thompson
Affiliation:
Commonwealth Institute of Biological Control
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Extract

This is the species referred to in the first Faper on the parasites of Archips cerasivorana (Can. Ent., Vol. LXXXV, No. 1, pp. 19-30) under the name Zenillia blanda. The genus Eusisyropa was created by Townsend (Smiths. Misc. Colls., Vol. 51, p. 97, 1908) with blanda O.S. as type. In it he also included boamiae Coq.. Aldrich and Webber (Proc. U.S. Nat. Mus., Vol. 63, Art. 7, 1924) placed these in Zenillia R.-D. but most workers agree that they collected a very heterogeneous assemblage of species under this name. As will be explained later, the efforts to subdivide the group on adult characters have not been entirely satisfactory. It seems best to use the restricted genera available until the matter has been studied in detail.

Type
Articles
Information
The Canadian Entomologist , Volume 85 , Issue 11 , November 1953 , pp. 393 - 404
Copyright
Copyright © Entomological Society of Canada 1953

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References

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.