Susceptibility of Screw-Worm Larvae and Prepupae to Desiccation

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Abstract
In the search for improved techniques for the mass production of screw-worm flies (Cochliomyia hominivorax (Coquerel)) for irradiation and release in an eradication program, one of the more elusive problems has been mortality of pupae caused by desiccation. It was found that the critical period of susceptibility to desiccation exists during the larval and prepupal stages (0 to 48 hours after larvae leave the rearing medium), and that losses sustained in the past can be attributed primarily to delay in providing protection. Screw-worms exposed as full-grown larvae to 90° F. and 40% R.H. for 48 hours suffered a weight loss of 53.5% and only 19.6% survived, compared with a weight loss of only 24% and 94% survival for controls protected with sand cover and room conditions of 85% R.H. A 24-hour exposure after pupation resulted in 31.9% weight loss and 61.4% survival in contrast to weight loss of only 16.1% and 93.7% survival for the controls. Screw-worms protected for 24 hours after pupation suffered minor losses when transferred to conditions of low humidity. Clarification of this critical period of susceptibility to desiccation should greatly improve handling of screw-worms after larval crawl-off and establish a firm basis for avoiding the serious loss from pupal mortality that occurred during the screw-worm eradication program in the Southeast.

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