Behavioural changes in Tityus stigmurus (Thorell, 1876) (SCORPIONES: BUTHIDAE) exposed to a pyrethroid insecticide

Chemical control remains a major management tool in limiting indoor infestations of scorpions in urban areas. However, information about the overall behavioural responses of these animals upon contact with insecticides, due to their neurotoxicological effects remains unclear. This study describes a set of stereotyped behaviours in Tityus stigmurus following exposure to a synthetic pyrethroid Type-1 (bifenthrin 20% w/v). We also investigated whether juvenile scorpions were more responsive than adults, if scorpions would be able to recognize and avoid the treated areas, and possible symptom reversibility. Animals were exposed to environments with and without pyrethroid treatment and their general behavioural changes, alteration in locomotion, and variation in motor activity were compared. Comb, chelicerae, and pedipalp cleaning following contact with treated surface suggests recognition of the insecticide; however, only juvenile individuals evaded treated areas. The main symptom of pre-intoxication was the reduction of mobility, followed by the release of a mucous substance through the chelicerae. Alterations in locomotion and motor activity were the most common behaviours during the intoxication phase, indicating the pyrethroid's neurotoxic effects, although these alterations were mostly reversible, particularly in adults. These results provide the underlying neurotoxic response of the urban scorpion T. stigmurus to bifenthrin, showing an age-specific tolerance and reversibility of toxic symptoms. Thus, for generalizations about the use of insecticides in combating scorpions, it is essential to understand the direct and indirect effects of the product on these animals.