ON CONIFEROPHAGOUS SPECIES OF CHORISTONEURA (LEPIDOPTERA: TORTRICIDAE) IN NORTH AMERICA: V. SECOND DIAPAUSE AS A SPECIES CHARACTER

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Abstract
The newly named C. biennis has a two-year cycle characterized by a second period of diapause at the end of the third instar. Second diapause occurs to varying degrees in C. fumiferana, C. occidentalis, C. orae, C. pinus pinus, and many of their hybrids, but has not been recorded in C. viridis. Although the incidence of second diapause can be influenced by the length of photoperiod to which larvae are exposed after completion of the second-instar diapause, second diapause occurring naturally is not primarily under environmental control. Laboratory studies have demonstrated differences in the incidence of second diapause manifested by these species and by some of their hybrids that point to the existence of genetic differences between them. This evidence supports the newly gained taxonomic status of these insects.