"Human foot odour was released from nylon socks (40 Den, 100% polyamide,
HEMA, The Netherlands) worn by WHS (laboratory experiments) or KJvR
(semi-field and field experiments) for 12 h prior to the experiments [6,12,13,26-29].
A clean nylon sock served as a control. Socks were placed along the
odour outlet tube of the MM-X trap without blocking the airflow and held
in position by odourless tape (3M™ Double Coated Tape 400; used in
laboratory experiments) or by a small metal wire (in (semi-)field