Comparative life-history studies of these two species (selected for study because they experience no nymph mortality on either healthy or diseased celery plants) show no significant differences in the duration of nymphal stages between specimens reared on healthy celery and those reared on diseased celery. In Colladonus montanus the total duration of nymphal stages is shorter for the males than for the females. In both species, males were smaller than females. C. geminatus and C. montanus do not interbreed.
