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148 J. E. Brittain 1-3 NYMPHS 01 I I 1 I I I I I A M J J A S O N MONTH Fig. 12. Life cycle of Nemoz~ra ovicularis in Burudvann (loc. 29). found in the Oslo region (Fig. 11). Small nymphs appeared in August and had reached a length of 2.5-3.0 mm by October. From October until May there was virtually no growth, the second period of growth taking ~lace in the month or so before their emergente during June and July. 10- r r E-1 NIMPYS Caenis moesta Bengtsson From the data available the life cycle of C. moesta is very similar to that of C. horaria. There are only small differences in mean size and size distribution of the two species. This may be a reason for the absence of bimodality in Moon's (1938) results for 'C. horaria'. PLECOPTERA Amphinemura standfussi Ris Amphinemura standfussi is a univoltine species which emerges later than many other lentic stoneflies. In Heimdalen emergence is concentrated in the month of ~u~ust and most growth takes place in the two months prior to emergence. Brinck (1949) and Benedetto (1973) record a similar situation from the mountainous and northern parts of Sweden, while in southern Sweden (Brinck 1949) the species is more hiemal. From northern Norway Sobias & Tobias (1971) registered adults during August. Nemoura avicularis Morton This species has a one-year life cycle in a wide range of localities. Its life cycle has NYMPHS ABSENT 01 I J J I A S o 1 MONTH Fig. 13. Life cycle of Nemon~a cinerea in Damtjern (loc. 22). 1' indicates adults taken. been studied in a number of countries and reviewed by Brittain (1973). In the lentic habitats investigated emergence took place soon after ice break, during May and June. The nymphs of the next generation 'are first found in collections during August and growth is then fairly rapid during the autumn, a length of 5-6 mm being attained by the beginning of November (Fig. 12). Nemoura cinerea (Retzius) Field studies of N. cinerea (Brinck 1949, Hynes 1961, Svensson 1966, and Benedetto 1973) have reported this species to be univoltine with a long emergence period and often a large spread in nymphal size. However, from laboratory studies, Khoo (1964) concluded that N. cinerea was semivoltine and demonstrated the presence of extended egg hatching and nymphal dormancy.
Ephemeroptera and Plecoptera 149 Fig. 14. Life cycle of Nemoura cinerea in Lake 1205 (loc. 18). 1. indicates adults taken. In lentic localities around Oslo emergence began by the end of May. At 850 m in Vassfaret adults were common at the end of June, whereas in the mountain localities adults were most abundant during July. In the lowland localities up to and including Damtjern in Vassfaret, N. cinerea showed a clear univoltine life cycle. For example, in Damtjern (Fig. 13) emergence began 2-3 weeks after ice break and continued well into July. Small nymphs appeared in September and reached an average length of 3 mm by the middle of October. By the spring there was considerable spread in population size, resulting in a relatively long emergence period. Above the tree line, however, the pattern became rather different. Emergence did not commence until the end of June, reached a peak during July, and continued as late as September. Small nymphs were already present in June, at the same time as mature nymphs. This bimodality was especially noticeable in Lake 1205 (Fig. 14). Eggs of N. cinerea from Lake 1205 were incubated in the laboratory at 10' C where they hatched after 25-26 days. The earliest emergence which could have physically taken place in Lake 1205 was, owin~. to the cover of ice, the beginning of June. Even at a temperature of 10' C, which is higher than present in the field at that time, small nymphs would not appear in collections until early July. However, by this time the average length of the nymphs in the field was nearly 3 mm (Fig. 14), having been present in collections since mid-June. 'he obvious conclusion is therefore that N. cinerea takes at least two years to complete its life cycle in such habitats. Thus little growth takes place during the first 9-10 months after oviposition. Most growth occurs during the following summer, from approximately 2 to 6 mm in length. If the species were univoltine in al1 localities it would be difficult to explain the larger mean size of populations during September and October in the higher situated localities where temperatures and also probably available food are lower. It is unlikely that temperatures in a habitat such as Damtjern reach values that are inhibitive to growth for any significant period. In fact, maximum-minimum thermometers were located in Damtjern and Lake 1205 during the period 17 July to 8 September 1971. For this period the maximum and minimum temperatures were for Damtjern, 17.2' C and 9.8' C, and for Lake 1205, 15.1' C and 5.5' C. A median temperature more than 3' C higher in Damtjern would explain the shorter incubation period and the more rapid initial growth, enabling it to complete its life cycle within a year. The nymphs, originating from the eggs hatched in the laboratory from Lake 1205, were kept at 10' C for a period. By the middle of November their mean length was 3.3 mm, a length which corresponds well with the length in Damtjern, rather than that in Lake 1205. Therefore it appears that the two life cycle types are determined primarily by environmental factors, of which temperature is of major importance. Nutritional factors are also probably of importance. o I 1 1 I I J J A S o MONTH Fig. 15. Life cycle of Nemu~ella picteti compiled from the summation of results from Lakes 1171, 1205 and 1220 (locs. 19, 18 and 16, respectively). + indicates adults taken. 10 - Norak ent. Tidsskr.
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Page 6 and 7: Dry Weight , mg. Fig. 7. Correlatio
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Page 16 and 17: 130 A. Fjellberg HABITATS Until now
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Page 22 and 23: 136 J. E. Brittain Fig. 1. The loca
Page 24 and 25: 138 J. E. Brittain period was longe
Page 26 and 27: 140 J. E. Brittain Table 11. Ph~sic
Page 28 and 29: 142 J. E. Brittain Table IV. Physic
Page 30 and 31: 144 J. E. Brittain EPHEMEROPTERA Am
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Page 36 and 37: 150 J. E. Brittain Nemzlrella picte
Page 38 and 39: 152 J. E. Brittain ture and the inc
Page 40 and 41: (Nord-Norwegen) (Trichoptera, Pleco
Page 42 and 43: from anoxia. Drops of haemolymph we
Page 45 and 46: Notes on little known spiders in No
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Page 49 and 50: Symphyla and Pauropoda 163 Table 11
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Page 63 and 64: Nocturnal moths 177 Grimstad Amli 1
Page 65 and 66: Nocturnal moths 179 Am/i. Norway 19
Page 67 and 68: Nocturnal moths 181 Grimstad, Norwa
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Page 80 and 81: 194 F. E. Klausen REFERENCES Ardii,
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198 A. Lillehammer Results The numb
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200 A. Lillehammer Fennoscandian co
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202 A. Lillehammer parts of the are
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204 A. Lillehammer carnivorous spec
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Table IV. Species distribution, in
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210 A. Lillehammer The bottom of th
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212 A. Lillehammer Blatjemn Diura b
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220 A. Lillehammer same latitude as
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222 A. Lillehammer Table XI. The pH
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224 A. Lillehammer These species se
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226 A. Lillehammer Table XVI. The s
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228 A. Lillehammer Fig. 22. Stream
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244 A. Lillehammer streams and rive
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246 A. Lillehammer Blies (1953, 195
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248 A. Lillehammer streams are to a
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250 A. Lillehammer Muller, K. 1955.
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252 Bokanmeldelser produserende, en
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N orsk Entomologisk Tidsskrift Norw
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