Influence of habitat structure on the phonotactic strategy of a parasitoid fly Emblemasoma auditrix

Abstract

Abstract. 1. Females of the parasitoid fly Emblemasoma auditrix find their host cicadas (Okanagana rimosa) using the acoustic signals produced by the host. The phonotactic behaviour of the parasitoid was studied with regard to differently structured habitats. 2. Habitats were modified experimentally within a distance of 2.5 m (approximately the natural range of phonotaxis) from a loudspeaker broadcasting a model of the host calling song. 3. Video analysis showed that in an open habitat (no landmarks) more than 60% of the flies performed a direct flight towards the loudspeaker. 4. In structured habitats (with one to three landmarks) more than 90% of the flies landed on their way to the acoustic target. 5. In about 50% of the landings flies paused for several seconds indicating re‐orientation during that time. Several flies included sequences of walking in their approach behaviour, whereby most walking occurred close to the loudspeaker. 6. In summary, the phonotactic approach and host finding depends on the habitat structure.

Phonotactic behaviour and vertical sound source localisation of the parasitoid fly Emblemasoma auditrix (Diptera: Sarcophagidae)

“…Emblemasoma auditrix seem to have a preference for using landmarks in its phonotactic approach, as more than 90% landed on their way to the target. Similar percentages of landings have also been reported for horizontal orientation in experimental habitats (Lakes-Harlan & Köhler, 2003). In the present study, we were able to show that landmarks are also used to adjust to the vertical height of the sound source.…”

“…The difference of the landing distances in the arena and the tree (see Fig. a) seem to be because of the natural landmark using behaviour (Lakes‐Harlan & Köhler, ). The flies tend to land closer to the target, if there is no prominent structure they could use as landmark (the second bin, 11–30 cm in the arena compared with the fourth bin, 51–70 in the tree).…”

“…Different experiments were performed: Use of landmarks for vertical orientation. Emblemasoma auditrix rarely flies directly to an acoustic target, rather they tend to land on vegetation at the range of 0.5–2 m from the target and stop at several plants on which they may perform a ‘rocking behaviour’ (tilting movements of the body from one side to the other; Lakes‐Harlan et al ., ; Lakes‐Harlan & Köhler, ) before they reach the target. In order to analyse the use of landmarks, we used a wooden stand with five perpendicular arranged sticks (1 cm in diameter, 40 cm long), each 20 cm apart (Fig.…”

Directional hearing: from biophysical binaural cues to directional hearing outdoors

“…A necessary word of caution should emphasize that the actual strategy of finding a host in nature may be more complex, as shown for another parasitoid fly Emblemasoma auditrix (Lakes-Harlan and Köhler 2003 ). In an open area, more than half of the animals flew directly to the loudspeaker (broadcasting a model song of their cicada host), but the presence of single landmarks reduced the percentage of direct flights to the target greatly.…”

The Auditory System of the Dipteran ParasitoidEmblemasoma auditrix(Sarcophagidae)

“…E. auditrix is a parasitoid of the cicada Okanagana rimosa (Say) and occurs in the Northeast of the United States and the Southeast of Canada during early summer. Gravid female E. auditrix acoustically locate the sound-producing males of the host cicada O. rimosa and infest them with a larva ( Lakes-Harlan et al 2000 , Lakes-Harlan and Köhler 2003 , Schniederkötter and Lakes-Harlan 2004 ). The larva feeds inside the cicada and eventually kills it before emerging to pupate in the soil ( Schniederkötter and Lakes-Harlan 2004 ).…”