Electroretinograms recorded from slowly moving insects like the mealworm beetle Tenebrio molitor and the stick insect Carausius morosus are shown to be distorted by the use of electrodes of stainless steel and silver/silver chloride wires, unless they are used in conjunction with amplifiers having extremely high input resistance. Undistorted electroretinograms can also be recorded using micropipettes filled with a suitable electrolyte. The undistorted ERG of Tenebrio molitor is monophasic, as described by Autrum (1950) for Dixippus, and as expected from his rule.

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