Shaking and lunging: Analysis of signaling by silk-spinning insects (Antipaluria urichi; Order Embiidina)

Embiid females have been seen lunging within their silk domiciles in response to natural threats. Field evidence suggested that egg-guarders are more likely to lunge than other embiids, and thus these putative signals appeared defensive. The purpose of this study was to develop methods to record substrate vibrations (the lunges) generated by females and to determine the context in which they are elicited. Vibrations were recorded in lab using piezoelectric film (a detector) connected to a computer. The detector was placed in an arena where a female was allowed to spin a domicile and lay her eggs. To understand the context of signaling, two factors were varied: intruder threat level and reproductive state of the resident. Intruder threat level ranged from high (adult female and nymphs who can devour eggs) to low (adult males who are not a threat because they do not feed). Reproductive state of the resident was either pre-reproductive or egg-guarding. Our predictions were that egg-guarders would be defensive and that nymphs and adult females would elicit signals because they represent a threat. As each intruder entered the arena, a continual record was made of vibrations and behavioral activities. In this presentation, signals are characterized using Audacity software. Behavioral data and signal attributes have been compared using a multivariate approach that elucidates key differences among the resident females in the different treatments. Results show that pre-reproductive residents do not signal as frequently as egg-guarding females. Egg-guarders signaled most vigorously to female intruders who were more reluctant to retreat. Actual attacks were rare suggesting that vibrations serve to communicate while eliminating the need for a real fight. Adult males elicited few signals even though they often entered the resident’s domicile to court the female. This is the first demonstration of communication in the order Embiidina.