Parameters of the seasonal cycle of Corythucha arcuata (Say, 1832) (Heteroptera: Tingidae) in the plains and foothills of the Northwestern Caucasus

Development of the first generation of Corythucha arcuata in the climate of the foothills and lowlands of the Northwest Caucasus starts in the early May. With a natural day length and the threshold for post-diapause imago development of 11 oC, it requires 333–404 degree-days and at least 43 days. The death of the overwintered females in this zone is observed by the end of June, coinciding with the reduction of the total portion of females to 2–7%. In the highlands imagoes are dispersing in June as well, surviving until July on willows and birch trees. Peak of the first-generation imago outcome occurs at the end of June. Migration of fertilized females of the first generation to new forage plants is followed by mass egg laying (i.e. beginning of the second generation). During the formation of large nests in the foothills, the flight of bugs is observed even in treeless highlands. Development of the preadult stages of the second generation (without changing feed plants) takes place starting at mid-June. Metamorphosis requires 361–430 degree-days and takes at least 16–23 days. The peak of the emergence of the second generation imagoes at the end of July coincides with their dispersal, which is also dominated by females. The third generation develops in August. It requires 329–350 degree-days and takes 19–28 days. The peak of the emergence of the G3 imagoes falls on the first third of September. It is preceded by an earlier emergence of males, determined by their mass local and regional migrations since the end of August. The fourth generation is obligated and develops (without changing feed plants) from the end of August to the end of September. It requires at least 378 degree-days and takes at least 26 days. Late nymphs resulting from female immigrant of the third generation (on new trees) give imagoes only by mid-October. The last migration of bugs is observed in early to mid-October. Imagoes of the third and fourth generations with the predominance of females hibernate in the oak forests of the foothills and low-mountain. In the midlands they may be accompanied by the overwintering immigrants of the second generation, with the predominance of males, formed in September.

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