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Abstract Ormia ochracea (Bigot 1889) is a phonotactic parasitoid fly that targets a variety of field cricket species as hosts for their developing young. Female flies locate their hosts by tracking a male cricket’s courtship song. Viviparous larvae are then deposited on or near the host which they then pierce and penetrate, completing larval development within the cricket’s abdomen. Here, we describe Ormia male and female reproductive tracts exposed through micro-surgery and imaged with a variety of microscopic techniques. We also describe for the first time, both embryonic and early larval development that takes place within the female flies’ “uterus.” Special note is made of the phenomenon of intra-uterine embryonic growth, and prospects for accessing gametes or germ-cells for molecular engineering are discussed. 

Abstract In parasitoid systems, resource competition can significantly impact developmental outcomes. This study investigates how larval competition and host characteristics influence development in the acoustic parasitoid fly Ormia ochracea, using the house cricket Acheta domesticus as a host. We experimentally manipulated larval load (1 vs. 2 larvae per host) and recorded host sex and size to assess their effects on pupation and eclosion (adult hatching) success, as well as pupal and adult fly size. While double infestations increased total yield (0.78 vs. 0.54 flies per host), larvae developing without competition exhibited higher relative pupation and eclosion success and produced larger pupae and adult flies, indicating greater individual fitness. Although female host crickets yielded larger pupae, resource competition was the dominant factor shaping developmental outcomes. These results highlight the trade-offs between reproductive yield and offspring fitness driven by resource competition and validate the commercially available A. domesticus as a viable host. 

Receivers of acoustic communication signals evaluate signal features to identify conspecifics. Changes in the ambient temperature can alter these features, rendering species recognition a challenge. To maintain effective communication, temperature coupling—changes in receiver signal preferences that parallel temperature-induced changes in signal parameters—occurs among genetically coupled signallers and receivers. Whether eavesdroppers of communication signals exhibit temperature coupling is unknown. Here, we investigate if the parasitoid flyOrmia ochracea, an eavesdropper of cricket calling songs, exhibits song pulse rate preferences that are temperature coupled. We use a high-speed treadmill system to record walking phonotaxis at three ambient temperatures (21, 25, and 30°C) in response to songs that varied in pulse rates (20 to 90 pulses per second). Total walking distance, peak steering velocity, angular heading, and the phonotaxis performance index varied with song pulse rates and ambient temperature. The peak of phonotaxis performance index preference functions became broader and shifted to higher pulse rate values at higher temperatures. Temperature-related changes in cricket songs between 21 and 30°C did not drastically affect the ability of flies to recognize cricket calling songs. These results confirm that temperature coupling can occur in eavesdroppers that are not genetically coupled with signallers.