Hi All,
I didn't see Layne's post but I would like to add to Garth's
explanation. Soap is a surfactant, eg. it changes the surface tension of
a liquid. In addition, soap also overcomes the natural repulsion of
water by an oily substance. Thus, soapy water "wets" the normally
waterproof exoskeleton of the insect, particularly the hairs covering
the spiracles or breathing holes. These hairs would normally prevent
water from entering the spiracles. The surface tension of water is not
breached by the hairs of the spiracles. Since insects respire directly,
that is, they cannot "hold their breath", they drown in soapy water.
Even aquatic insects will drown in soapy water.
Dave General
Cagayan de Oro City
Philippines
16-year beekeeper
 
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