CHEMORECEPTION IN INSECTS AND THE ACTION OF DDT

¹ Department of Biology, Tufts College, Medford 55, Mass.

1. DDT appears not to stimulate sensory endings, but makes them capable of repetitive discharge following stimulation with toluene and benzene.

2. Pretreatment with DDT lowers about nine-fold the sucrose acceptance thresholds of DDT-sensitive houseflies and blowflies. Sucrose thresholds of resistant flies are unaltered.

3. Pretreatment with DDT does not change salt or alcohol rejection thresholds, either against sucrose or water.

4. Under certain conditions clean smooth surfaces can evoke feeding behavior similar to that in response to acceptable chemicals.

5. DDT-sensitive houseflies, given a choice, spend a greater amount of time on DDT-treated areas. Resistant flies do not. Surfaces treated with DDE and 1,1-bis (p-chlorophenyl) ethane are not discriminated from control surfaces.

6. It is concluded that acceptable and unacceptable compounds are perceived through different sets of receptors.

7. The proboscis extension reflex is not controlled by chemoreceptor activity alone, but also by tactile stimuli.

8. The failure of DDT to affect reflex behavior of this strain of DDT-resistant houseflies is not due to failure to penetrate the cuticle, but must be due to some mechanism intrinsic to the nervous system.