The influence of temperature on the post-diapausal development and survival in the aestivating eggs of Halotydeus destructor (Acari : Eupodidae)

Abstract

After diapause development is complete, moistened aestivating eggs of H. destructor develop successfully within the temperature range 5-20.5C. The rate of development up to the deutovum stage increases with temperature up to about 20C and then rapidly decreases. Eggs will tolerate temperatures between 25 and 31.5C for up to 53 days without undergoing morphogenesis, but this treatment retards subsequent development at 16C. Exposure to alternating temperatures accelerates the rate of development but, if the higher temperature exceeds 20.5C, development is retarded. The effect of temperature on the rate of development within the deutovum stage is similar to that on non-diapause winter eggs throughout their morphogenesis. Air-dry eggs will tolerate temperatures up to 75C but moist eggs are killed by exposure for 1 day to 45C. This high temperature tolerance, together with the limitations on development imposed by temperature, ensures that the aestivating eggs do not hatch before early autumn, even in the event of unseasonal summer rain. The temperature response curve and its ecological significance are discussed briefly.

Predicting the timing of first generation egg hatch for the pest redlegged earth mite Halotydeus destructor (Acari: Penthaleidae)

“…Halotydeus destructor are not found in January or February as the oversummering eggs will generally not have had sufficiently hot conditions to terminate diapause (Wallace 1970a). Temperature has a profound influence on the development of aestivating eggs of H. destructor (Davidson and Swan 1943;Norris 1950;Wallace 1970b). Wallace (1970b) found that the pre-deutovum stage of aestivating eggs was more sensitive to higher temperatures than the shorter deutovum stage.…”

“…Temperature has a profound influence on the development of aestivating eggs of H. destructor (Davidson and Swan 1943;Norris 1950;Wallace 1970b). Wallace (1970b) found that the pre-deutovum stage of aestivating eggs was more sensitive to higher temperatures than the shorter deutovum stage. The favourable temperature range for morphogenesis in the pre-deutovum stage is 5°C to about 20°C, with optimum developmental rates occurring around 19°C.…”

“…1 Influence of temperature on the duration and rate of development up to the deutovum stage of moistened, post-diapause eggs of Halotydeus destructor, reworked from experiments by Wallace (1970b). Development rate profiles were provided for four different experiments; all data points were extracted from Fig.…”

“…Development rate profiles were provided for four different experiments; all data points were extracted from Fig. 2 in Wallace (1970b), using the graph digitiser software xyExtract (v 3.1, Wilton Pereira da Silva, Brazil), and a single line of best fit was overlaid Exp Appl Acarol (2015) 65: 259-276 261 (commonly pasture legumes and broadleaved weeds) that commence their growth in autumn or early winter. Because this pest attacks a wide range of legumes, grasses and broadleaved weeds (Ridsdill-Smith 1997), it is rarely limited, in the classical sense, by availability of host plants.…”

“…Swan (1934) observed that eggs require moist environments to complete development. Wallace (1970b) implied that some rainfall, followed by appropriate declining temperatures, is necessary to trigger egg hatch. Wallace suggested H. destructor has evolved strategies to avoid egg hatch following late summer or early autumn rainfall in the absence of declining temperatures to below 20.5°C.…”