Untersuchungen über die Eiparasiten (Hym.: Chalcidoidea) der rotgelben Kiefern-BuschhornblattwespeNeodiprion sertifer Geoff. (Hym.: Diprionidae)

Abstract

1. Four or five species of egg parasites ofNeodiprion sertifer have been found in central Europe. 2.Dipriocampe diprioni is a primary parasite which overwinters as a first instar larva within the host's egg, The larvae complete feeding in early spring and enter an obligatory diapause which lasts until July–August. Under the influence of the parasite, the egg shell of the host turns brownish. The adults emerge from mid-August onward. The univoltine parasite is thus well synchronized with its major host,N. sertifer. 3. A second species, or form, ofDipriocampe has been found, the taxonomic status of which is still unresolved. It is here referred to asDipriocampe sp. forma ignorata. Although not yet separable fromD. diprioni morphologically, its biology is quite different. The larvae mature before the winter and the adults emerge in April–May of the following year, being dependent on alternate hosts. This form is exceedingly rare in lowland areas but possibly common at high altitudes. It remains to be seen whether it is a separate species or a polymorphic, non-diapausing form ofD. diprioni. Host eggs attacked byDipriocampe sp.forma ignorata turn blackish. 4. Two species ofAchrysocharella have been found,A. ruforum andA. ovulorum. In lowland areas,Achrysocharella spp. attack the eggs ofN. sertifer in a hyperparasitic capacity, developing at the expense of the larvae and pupae ofDipriocampe spp. or of larvae and pupae of their own kind. There are two or three such hyperparasitic generations during the summer, the last entering hibernation before the new eggs ofN. sertifer make their appearance, thus failing to attack them in a primary capacity. In mountainous areas, where the eggs ofN. sertifer appear earlier,Achrysocharella spp. pass the first generation as primary parasites in the sawfly eggs, and the second (summer) generation as hyperparasites of larvae and pupae ofDipriocampe spp. or of larvae and pupae of their own kind. 5.Tetrastichus oophagus has been associated with the eggs ofN. sertifer in a few cases only, but has been more common as a parasite of the eggs ofDiprion pini. 6. The importance of the egg parasites ofN. sertifer has to date been underestimated. Egg parasitism is apparently density-dependent and can reach high values during, and immediately after, the break-down of the sawfly populations.