20 B. C. ENTOMOLOGICAL SOCIETY 



A SWARM OF VANESSA CALIFORNICA 

 AND SOME NOTES ON A SWARM OF PLUSIA CALIFORNICA 



By J. W. Cockle 



Commencing on June 17th of this year a very large number of 

 V. californica were to be seen on the lower slopes of the mountains 

 round Kootenay Lake. It is usual to see a few hibernated specimens 

 of this butterfly in the early spring, just as soon as the weather is warm 

 enough to permit them to emerge from their winter quarters, but what 

 amounted to a large swarm in the middle of June was most unusual. 

 All of the specimens were very fresh and looked as if they might be 

 freshly emerged, but my supposition was that they were part of a brood 

 that had hibernated at a very high altitude and consequently did not 

 leave their winter quarters until the snows had melted in the neighbour- 

 hood in which they had hibernated. This supposition is backed up by 

 the fact that the mountains round Kootenay Lake rise to an altitude of 

 over 9,000 feet and their only known food plant, Ceanothus sanguineus, 

 grows most abundantly up to near the summits. 



About the first week in August the new brood began to make their 

 appearance and in a few days they were to be seen in countless thou- 

 sands, not alone round Kootenay Lake but eastward across the mountain 

 range in the valley of the Columbia and westward into the valley of 

 the Arrow Lakes district. The emergence seemed to reach its zenith 

 about the 15th of August, at which time they were everywhere; along 

 the roads in the afternoon they were to be seen settled on the roadbed 

 in sufficient numbers to almost obscure the ground. 



I kept a good lookout for any aberrations but none were seen, 

 whereas in the swarm that was here in the summer of 1890 several 

 dimorphic specimens were captured by a collector here; these are, I 

 believe, now in the Cambridge Museum in England. 



The time of their arrival and subsequent emergence shows that 

 their entire larval and pupal stages were completed in five weeks ; this 

 is remarkable as those that occur here ordinarily will take from the 

 beginning of May until August to complete their life-history. 



I have also to record a swarm of Plusia californica which emerged 

 at the end of September. They were much in evidence in the afternoon 

 and early evening flying over the clover, as many as twenty or thirty 

 might be taken on the clover blossoms within a space of a square yard. 

 Though they were so plentiful in the fields, they were very scarce at 

 light, which is quite the reverse of their usual habit. It was curious 

 that P. californica was so numerous, when the scarcity of all other 

 varieties of Plusias was so marked, the only other species of this genus 

 that occurred sparingly here last summer was viridisignata, all other 

 members of this family were conspicuous by their absence, not a single 

 specimen was taken here by either of the collectors. 



