Norwegian Journal of Entomology Norsk Entomologisk Tidsskrift EDITOR Dr. philos. Lauritz Semme, Zoologisk institutt, Universitetet i Oslo, Blindern, Oslo 3, Norway. EDITORIAL COMMITTEE Fsrstelektor Eivind 0stbye, Konsulent Per F. Waaler, Ferstekonservator dr. philos. Albert Lillehammer. PUBLISHER Universitetsforlaget: P. O. Box 7508, Skillebekk, Oslo 2, Norway. P. O. Box 142, Boston, Massachusetts 02113, U.S.A. CONTRIBUTIONS These should be sent to the Editor. Authors are requested to follow the instructions on page 3 of the cover. Artikler som snskes trykt i tidsskriftet sendes redaktsren. Bidragsytere ml fslge anvisningen pi omslagets tredje side. SUBSCRIPTIONS Non-members of the Norwegian Entomological Society should send their orders to Universitetsforlaget. The subscription price per volume (two issues annually) is for 1977 US. $ 15.00 (N. kr. 75.-). U.S. $ price is subject to change without notice in case of devaluation/revaluation. Notice of change of adress should be accompanied by the old address. Back volumes should also be ordered from Universitetsforlaget. NORSK ENTOMOLOGISK FORENING ser sin hovedoppgave i I fremme det entomologiske studium i Norge, og danne et bindeledd mellom de interesserte. Medlemskontingenten er for tiden kr. 40,- pr. ar. Medlemmer fAr tidsskriftet fritt tilsendt. Henvendelser om medlemskap sendes sekreta:ren: Cand. real. Trond Hofsvang, Zoologisk institutt, NLH, 1432 As-NLH. lC Univenitetsforlaget 1977 E. SEM A/S. HALDEN Cold storage tolerance and supercooling points of mummies of Ephedrus cerasicola Stary and Aphidius colemani Viereck (Hym. Aphidiidae) TROND HOFSVANG & ELINE BENESTAD HAGVAR Hofsvang, T. & Hagvar, E. B. 1977. Cold storage tolerance and supercooling points of mummies of Ephedrus cerasicola Start and Aphidius colemani Viereck (Hym., Aphidiidae). Norw. ]. Ent. 24, 1-6. EphedrUJ cerasicola Start, parasitizing Myzus persicae Sulzer, is well suited for storage at 0 ± 1DC as (}-2 day-old mummies. Subsequent emergence at 21 DC occurred from 60-90% of the mummies stored for 1, 2, 3, 4, and 6 weeks. Storage for 8, 10, 14, 18, and 22 weeks successively reduced the percentage emergence from 46% to 2010. The emerged females produced significant amounts of fertilized eggs at room temperature even after 14 weeks' cold storage of the mummies. When 4-5 day-old mummies were stored at 1DC, normal emergence occurred at 21 QC from those stored for 1 and 2 weeks. However, emergence was reduced to 30% and 0% after 4 and 8 weeks' storage respectively. Mummies of Aphidius colemani Viereck are not suited for long-term cold storage because of too low emergence at 21 DC after storage at O°C, 4°C, and 7°C and too fast development during storage at 7°C and lO°C. The average supercooling points of E. cerasicola and A. colemani were -26.1 DC, SD = 1.3 and -25.4°C, SD = 0.9, respectively. Acclimation for 1 week at -5°C lowered the supercooling point in E. cerasicola mummies to -29.4°C, SD = 1.9. Trond Hofsvang & Eline Benestad Hdgvar, Agricultural University of Norway, Department of Zoology, p.a. Box 46, N-1432 As-NLH, Norway. Successful storage of parasites at low tempera­ ceipes (Cresson) tolerated storage of low tures has practical importance in biological temperatures better than adults. control. It is a simple method to keep para­ In the experiments presented in this paper, sites alive when they are of no use, e.g. out­ mummies of the aphidiid parasites Aphidius side the greenhouse cultivating season. In colemani Viereck and Ephedrus cerasicola this way they may also be more easily ship­ Start were stored at low temperatures. Both ped, and the costs of transportation may be species readily attack the green peach aphid lowered because the time factor is less im­ Myzus persicae Sulzer in Norwegian green­ portant. Furthermore, the synchronization of houses. Parts of the biology of these two emergence for mass release programs is fa­ species, such as longevity, developmental rate, cilitated by such storage. It has been shown fecundity and oviposition pattern, have pre­ that low storage temperatures may increase viously been studied (Hofsvang & Hagvar the reproductive potentials in some parasitic 1975, a, b, c). In these papers A. colemani Hymenoptera (Legner 1976). Even tropical was named Aphidius platensis Brethes, but species seem to have some advantages by A. platensis is now considered as a synonym such treatment (Legner 1967). of A. colemani (Start 1975, 1976). Aphidiid parasites are easy to handle as The world distribution of A. colemani mummies, and mummies are well protected covers mediterranean Europe, parts of Asia, from external injuries. Probably the most Africa, Australia, and South America (Start common case of arrested development in 1975). Its introduction into our laboratory aphidiids in cold winter areas is hibernal stocks was accidental (Hofsvang & Hagvar / quiescens inside the cocoon of a mummified 1975 b). It is uncertain if this species can / aphid (Stary 1970a). Archer et al. (1974) survive the winter outdoors in Norway. found that mummies of Lysiphlebus testa- E. cerasicola is widely distributed in Europe 1 - Norsk ent' Tids8k.r. 2 T. Hofsvang & E. B. Hagvar (Mackauer & Start 1967), most probably in­ tures were 10° and 4°C, and cold storage cluding Norway. It is assumed that this spe­ temperatures were 10°, 7°, 4°, 1°, and O°C. cies hibernates in Norwegian areas inside a At O°C the temperature was not constant, mummified aphid. fluctuating between + 1° and -1 0, but was on average about O°C. Acclimation and cold storage were performed in darkness. After storage, the mummies were trans­ MATERIAL AND METHODS ferred to an incubator at 21°C, 16 hrs photo­ The parasite species used in the experiments period, for emergence. In order to check their were taken from laboratory stocks at room reproduction ability after storage, some of temperature, in which they were parasitizing the emerging females and males were trans­ M. persicae on swedes (Brassica napus napo­ ferred to a cage at room temperature, con­ brassica (L.) Rchb.) or paprika (Capsicum taining an aphid-infested swede or paprika. annuum L.). The sex of the progeny was also determined. In the cold storage experiments, newly Tolerance to extreme low temperatures formed mummies from swedes, at most 1 day was tested by measuring supercooling points old, were placed in groups of ten in a dram of the mummies, taken from swedes at room vial plastic lid which was put on moistened temperature, by placing them in contact with filter paper in a petri dish (5.5 X 2.5 cm). a copper-constantan thermocouple connected Some mummies, kept in this way, were then to a recording potensiomefer (Somme 1964). put in cold storage conditions, some were The cooling rate was about 1°C per minute. acclimatized for two days prior to cold stor­ Supercooling points were first measured on age, and some were kept at 21°C, 16 hrs 20 untreated mummies of each species. The photoperiod, to obtain desired age at the age of the· mummies was unknown. start of cold storage. Acclimation tempera­ The effect of acclimation at low tempera- Table I. Percentage emergence at 21°C from mummies of E.cerasicola, taken from swedes and stored at low temperatures for different time periods. At each time period, n=50, except in series 1 where n=100. Series 1 2 3 4 5 Acclimation 2 days at 4"C 2 days at 4°C No accl. No accl. No accl. Storage temp. O"C l"C l"C 1°C l"C Age of mummies at storage (days) 0-1 0-1 0-1 1-2 4-5 -­ Weeks stored 1 90 82 82 2 79 60 76 82 80 3 64 4 71 70 86 60 30 6 69 8 46 48 42 40 0 10 31 46 34 14 16 38 30 18 3 22 2 no accl. or storage 62 Cold storage tolerance 3 tures on the supercooling point was tested for increasingly detrimental effect on the emer­ E. cerasicola only. Groups of 25 mummies, gence percentage. at most 2 days old, were kept at 0° for two Acclimation of mummies prior to the stor­ weeks or at _5°C for one week before the age did not affect the emergence (series 1, supercooling points were measured. During 2, and 3 in Table I). acclimation, the mummies were kept in small No effect of the age could be demonstrated glass tubes plugged with cotton, placed in for mummies stored up to 2 weeks. However, tight glass jars with moist cotton in the emergence was reduced with increasing age bottom. To control survival after acclimation, of mummies both after 4 and 8 weeks' stor­ 25 additional mummies were stored under the age (series 4 and 5). same conditions, but were then transferred Apparently, no development occurred at to 21°C, 16 hrs photoperiod, for emergence. O°C in E. cerasicola (series 1). After being Several experiments on supercooling points brought to 21°C, the adults emerged after 8­ with different acclimation conditions were 10 days, which is about normal time of de­ excluded because of low emergence from velopment for mummies at this temperature control mummies. Differences in supercooling (Hofsvang & Higvar 1975 a). points were tested by the Student t-test. In series 1, which was most complete and Some of the emerged adults were released based on most mummies, the 9-/ ~ ratio of on paprika plants and their progeny was emerging adults after cold storage was well counted and the sex determined. above 1 for mummies stored up to 10 weeks. Without cold storage, the sex ratio was 0.9. For practical application, it is important to RESULTS know whether cold storage of mummies inter­ feres with the progeny production of the Cold storage of mummies emerging adults.