Since the series of behaviors and physiological interactions that control reproduction are coordinated by the nervous system, most insecticides affect insect reproduction to one degree or another (for example, mate location, courtship, and oviposition behaviors may be affected; Haynes 1988).

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The effect of malathion dosing on the mating behavior of the lycosid spider, R. rabida was tested in our laboratory. Adult R. rabida were exposed to 10 ul of 10^-4 malathion for 24 hours and their responses compared to control animals. In the first experiment, the effect of malathion on males was tested (dosed males, normal females). Males were first tested for response to female pheromone alone, then in an arena with normal females (Tietjen 1979, Tietjen & Rovner 1982).

In the second experimental series the responses of dosed and undosed females to a standard male was explored. The standard male was generated by videotaping a male’s courtship "dance" from a camera angle similar to a female’s point of view and then digitizing a sequence as a computer movie (an "AVI" file at 30 frames per second). This allowed us to position the video near the female during playback and enabled us to easily change the size to approximate that of a typical male. In addition, the file could be set to play in a loop so the female received a standard courtship sequence. These precautions eliminated variations in male courtship response as a confounding factor in the analysis. Courtship vibrations were played back using a speaker positioned under a false bottom of the females’ test arena; thus females were exposed to both visual and audio components of a standard male courtship display.

A female R. rabida responds to a video male.

In the third experiment both males and females were dosed with malathion and their responses were compared to those of normal pairs.

A female R. rabida rejects a courting male (both were dosed).

The pheromone-mediated responses of male R. rabida differed among dosed and undosed animals (SEMs of spider pheromone receptors can be seen here). In addition, normal females paired with dosed males killed 95% of the males without mating, while none of the normal males were killed (and all mated). It is interesting to note, however, that normal female interest in dosed males (first notice time and distance, time latency to accept the male, etc), was not significantly different from their responses to normal males. However, when dosed males were accepted by normal females, they did not switch to mating behavior but instead retreated from the female only to immediately resume courtship behavior. After three to five acceptance attempts, the females usually killed the males. Undosed males all began mating within 20 min while the two surviving dosed males did so only after 45 min. Dosed females tested with standard "video" males showed increased variability in response parameters (including approach times, distance when the male was first noticed, and time until they lost interest). When both males and females were dosed, 25% of the males were killed and 33% of the remaining dosed pairs never mated.