Transrectal ultrasonic planimetry of the prostate in relation to age and lower urinary tract symptoms among elderly men in Japan

We investigated the responses to insect prey (dead houseflies) in 24 "derivative groups" of workers of the ant Formica polyctena created by taking sets of 25 workers out of nine larger "initial groups" kept in laboratory without queens and brood during the preceding five months. In the derivative groups the ants ceased to retrieve flies to their nests after a period ranging from few days to several weeks. The duration of that period did not depend on the present size of the derivative group (decreasing as a result of worker mortality), but was positively correlated with the estimated size of the initial group of the tested ants. The readiness to display venom spraying was higher in smaller derivative groups. These data demonstrate that responses of F. polyctena to insect prey are strongly influenced both by the present and the past size of their group.