216 Observations on ri)ni)la pomorum 



It is noteworthy that all of some eighty unparasitised examples of 

 the host weevil, reared during this investigation, emerged from the pupa 

 prior to the appearance of the Pimpla, none issuing later than June 13th. 



After the emergence of the perfect insects, the subsequent life of the 

 species is a mystery. It is perfectly clear that there is no available supply 

 of the larvae or pupae of the weevil until the following year. It appears 

 improbable that the adult parasite awaits a period of about ten months 

 for the reappearance of its larval host. Most probably it utilises an 

 alternative species, and passes through a second annual generation, 

 though what that host is likely to be is hard to predict. 



A further point of interest is the fact that the parasite occurs in dis- 

 tricts where Anthonomus pomorum is unknown. For example in Suffolk, 

 according to Morley (1908, p. 77), this weevil is absent, nevertheless the 

 parasite is a common insect in that county, and may be frequently 

 beaten out of Coniferae. Nothing, however, is known regarding the host 

 which it utilises on such occasions. 



In this connection some clue may possibly be afforded if we take into 

 account the various hosts utilised by other species of the genus Pimpla. 

 There is no doubt whatever that Lepidoptera are usually selected and, 

 out of the forty British species of Pimpla, which are enumerated by 

 Morley (1908, pp. 51-118), the vast majority have been bred from various 

 members of this order of insects. The most usually parasitised species are 

 Retinia huoliana, R. resinana, Tortrix viridana, Orgyia cmtiqua, Odonestis 

 potatoria and Clisiocampa neustria. Many other species, however, serve 

 as hosts and great variation is exhibited in the size of the host selected. 

 Thus Pimpla rufata Gmeb. has been bred from Tortrix viridana and the 

 relatively gigantic Sphinx ligustri; and P. instigator Fab. from Psyche 

 viciella and Smerinfhiis populi ! Outside the order Lepidoptera there are 

 few reliable records; four British species of Pimpla have been bred from 

 the egg masses of spiders and about six species have been reared from 

 Coleoptera, almost exclusively Curculionidae. With the exception of 

 Pimpla pomorum. these latter species have been reared from Lepidopterous 

 hosts also. Of the species known to parasitise Anthonomus pomorum the 

 following host records are enumerated by Morley (1908, pp. 60, 81, and 

 99). Pimpla gram inellae has been reared from Odonest is potatoria, Epippi- 

 phora scutulana (or E. pjlugiana) and Clostera reclusa. Pimpla sagax has 

 been reared from Retinia huoliana, R. resinana, R. turionana, Coccyx 

 cosm,ophorana, Tischeria complanella, Conchylis posterana, and Litho- 

 colletis trifasciella. Morley (loc. cit. p. 81) also records an example bred 

 on April 26th from dried heads of Centaurea nigra gathered beneath 



