Abstract: A species-selective field trap for flies which comprises a receptacle (1) having a removable lid (4), the receptacle forming a substantially closed chamber(s), when the lid is in place, within which a source of chemical attractant vapor attractive to the selected species of fly and unattractive to most other species of fly is positioned in use. The receptacle having a substantially opaque upper, in use, end (2, 4) which is colored as a visual attractant to the selected species of fly and having one or more small apertures (6) in a side or the lid, thereof adapted to closely accommodate passage of the selected species of fly therethrough. The apertures being the primary and preferably the only means by which the chemical attractant vapor is emitted from the receptacle.

Abstract: A method of tracing sewage effluent is described in which samples of fluid flows are subjected to high performance liquid chromatography with respective elution systems capable of eluting different selected compounds therefrom, and the concentration of each compound in the sample is determined spectroscopically. The method is used to determine sewage flow paths in natural water bodies, such as rivers, to check for contamination by sewage, to determine possible sewage sources, the detection of uric acid, for example, being indicative of a human source; and to monitor the effluent from sewage treatment plants.