Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosure
b. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosure
b.

Placing a MALE SNOWY TREE CRICKET in enclosure B is part of the control group.

Placing a FEMALE SNOWY TREE CRICKET in enclosure B is part of the experimental group.

Explanation:

In scientific method of experimentation, a control group can be described as a group which is not changed so that it can be compared with the experimental group and changes in the experimental group be easily depicted. If male snow tree cricket are placed in enclosure B, this means that the experiment is a control group as no changes are being made.

An experimental group can be described as the one in which changes are made. It comprises of dependent and independent variables.

that is wrong, its not thymus.