Gregarina typographi (Eugregarinorida: Gregarinidae) in the bark beetle Ips typographus (Coleoptera: Curculionidae): transmission in nuptial chambers

Changes in Gregarina typographi Fuchs, 1915 (Eugregarinorida: Gregarinidae) infection levels were studied in a population of the bark beetle Ips typographus (L., 1758) (Coleoptera: Curculionidae), which lives in association with Norway spruce. Beetles were repeatedly collected from three logs of trap trees during 2009 and 2010 at one study site in the Czech Republic with a high level of G. typographi infection (seasonal mean of 15.7% in 2009 and 19.8% in 2010). Infection levels did not differ statistically between sexes, logs, and trap trees but did differ among sampling dates. During the beetle reproductive period, the infection levels nearly doubled in 2009 (from 10.7 to 19.8%) and more than tripled in 2010 (from 9.3 to 31.3%). We infer that the continuous increase in the G. typographi infection level within each of the two years resulted from transmission among beetles in nuptial chambers during the May–June reproductive and egg-laying period.