Effect of age of the intermediate host Tribolium confusum (Coleoptera) on infection by Hymenolepis diminuta (Cestoda).

A cross-sectional study of 27 cohorts of Tribolium confusum aged 2-78 wk was done to examine effects of host age on exposure to eggs of Hymenolepis diminuta under standardized conditions. Pre-exposure, fasting, and postexposure mortality were low, sex ratio was equal, and fecundity of hosts was high during the first 30 wk, followed by increasing mortality and male bias of the sex ratio, and declining fecundity, in older beetles. These changes in the host were not associated with pronounced changes in infection results. Prevalence of infection was higher in females than males, but was unaffected by age in both sexes. Intensity of infection was similar between sexes in beetles up to 30 wk old, and thereafter declined in females, but not in males. Age-related changes in hosts were gradual, but unexpected levels of short-term variation in infection results suggest that some undetermined proximate factors may override general host age effects on the infection process.