80 



egg do not find there the conditions requisite for normal development, 

 though the root-infesting generations can adapt themselves to the 

 native vines and to the local weather conditions. 



v" Stellwaag (F.). Die Schmarotzerwespen (Schlupwespen) als Para- 

 siten. [Parasitic Hymenoptera.] — Monographien ziir angeic. Ento- 

 mologie, no. 6, Beiheft no. 2 to Zeitschr. angew. Ent., Berlin, vii, 

 1921, 100 pp., 37 figs. [Received 6th December 1921.] 



In this discussion of Hymenopterous parasites, the systematic 

 position and habits of the adults are considered only so far as is 

 necessary, while development in the egg and larval stages and relation 

 to environment are dealt with at length. 



The female genitaha and the deposition of eggs form the subject of 

 the first chapter. It is pointed out that no insect host is in any way 

 protected against these enemies. The second chapter deals with the 

 development of the early stages, and contains information on the 

 physiological relation of the host to its parasite. The economic 

 value of these Hymenoptera depends on their relation to their sur- 

 roundings, and this subject is discussed in the third chapter. It may 

 be generally accepted that parasites can flourish wherever the conditions 

 permit the host to develop. When considering the influence of climate 

 on geographical distribution it is necessary to distinguish between 

 distribution areas as represented by climatic limits and specific areas 

 where the species have been actually taken. In the United States 

 many species of Pteromalus have been bred from Lymantria dispar 

 and Nygmia phaeorrhoea {Enproctis chrysorrhoea) , though they are 

 scarcely known in Germany, where they should be very common. 

 As a rule the adult parasite appears before the stage of the host which 

 is of importance to it. Monophagous egg-parasites with a host with 

 a one-year generation require about one year to develop \vithin the 

 host-egg. This is actually the case with Anasiaiiis hifasciatus, Boy., 

 the larva of which is full-grown in three weeks, but does not give rise to 

 the adult until ten months afterwards, when emergence from the 

 host-egg takes place. Ageniaspis fiiscicollis, Dalm., hitherto obtained 

 only from Hyponometita spp., has a one-year generation like its 

 hosts, but the subspecies, A. fiiscicollis praysincola, Silv., has three 

 generations like its host, the olive-moth [Prays oleelhis). 



Schwangart has drawn attention to the possibility of combating 

 vine-moths by growing the food-plants of intermediate host-insects 

 in vine-growing districts [R.A.E., A, viii, 353, 356]. This view is 

 supported by the fact that in the Palatinate and in South Tyrol, 

 both regions where other plants are grown close to vines, parasitism 

 may amount to 30 per cent, instead of only 1 per cent., as in the 

 Rhine Palatinate. 



Hyperparasites play an exceedingly important part, but as they 

 may also occur as primary parasites, or as superparasites, it is not 

 always a simple matter to assess their value. In cases of superpara- 

 sitism it appears that the larvae of Hymenopterous parasites can 

 occur together with more compatibility than is the case when Tachinid 

 larvae are present. 



The last chapter contains the following lists of parasitic Hymenop- 

 tera : Species with aquatic hosts, Chalcids infesting plants, species 

 bred from Prays oleelhis, species infesting the vine-moths (Clysia 

 ambiguella a.nd Poly chrosis hotrana) , Sparganothis {Oenophthira)pilleriana , 



