The deimatic reaction in the praying mantis Stagmatoptera biocellata

Abstract

When the mantid Stagmatoptera biocellata is shown a foe, the insect displays a characteristic response called the deimatic reaction (DR) (Fig. 1). A systematic study of the response is presented in this paper. 1. The full display is an assembly of seven independent and very stereotyped components. The lesser the strength of the reaction, the smaller the number of components. They disappear in a stereotyped order. 2. The occurrence of the DR proved to be highly predictable using birds as releasers (i.e. troupials, shiny cow-birds, Java sparrow and canarys). But the DR was also induced by the back projection of real or filmed shiny cow-birds silhouettes. Only a film taken and projected at 100 frames a second induced a DR as a “real” stimulus. 3. A DR is immediately induced by a bird presented for 2 minutes. The response duration exceedes the presentation interval. The leftover time ranged from few seconds to 45 minutes. When the insect and the predator were faced for long time, the DR was displayed as long as the stimulus was shown and a response that lasted 6 hours was recorded. Some conclusions were deduced from testing crude interferences in the nervous system (Fig. 3). Namely, that the DR can be elicited either by visual and tactile stimuli, and that the movements involved in the display are not coordinated with each other in a closed-circuit system. This finding is discussed in connection with an hypothesis put forward by Vowles (1961). 4. The survival value of the DR is analyzed and the paper concludes, unlike previous reports, that the over-all effect of the display is to frighten the foe.