Startle response in the Colorado potato beetle, Leptinotarsa decemlineata (Say)(Coleoptera: Chrysomelidae)

• Main Author: Acheampong, Susanna
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1994
• Subjects: Entomology; Neurology; Neurosciences; Zoology
• ISBN: 9780612111417; 0612111415

The startle response in the Colorado potato beetle, Leptinotarsa decemlineata (Say) was induced by dropping bell sinkers with weights varying from 14-134g on a support on which beetles rested and by controlled stimuli from a large acoustic speaker. Results from preliminary experiments showed that recovery from the immobile state was either preceded by leg or antennal movement. The time taken for beetles to come out of the immobile state (i.e. recovery time) was not dependent on age or sex, though pre-startle behavior did affect recovery time. The stimulus caused by a falling sinker was in the form of sine waves with a frequency of 110Hz for all sinkers used. A more controllable device was thus designed to startle beetles. The set-up involved the use of a loudspeaker, frequency generator, frequency counter, timer and amplifier. 30Hz was found to be the most effective frequency for startling beetles. Recovery time was not affected by stimulus duration, but was dependent upon displacement and satiation level of beetles. Starved beetles took a shorter time to recover than fed beetles. Repeated presentations led to a trend of sensitization followed by habituation. Eyes and antennae are not involved in the detection of vibration. A chordotonal organ is present in the trochantero-femoral joint of all three legs and a novel mechanosensory organ only in the forelegs. Results of amputation experiments showed that the novel organs were not the only organs involved in the detection of the startle stimuli.