1.1. A hemolysin found in whole fly homogenates and in midgut homogenates of Stomoxys calcitrans (L.) is heat labile, has a slightly acidic pH optimum, and is non-dialyzable.2.2. Hemolytic activity is enhanced by dialysis but not by removal of Ca2+ alone.3.3. The hemolytic curves obtained are sigmoidal, which suggests some cooperative acivity.4.4. This hemolysin is activated by addition of trypsin to the homogenates.

An insect growth regulator, (E)-6,7-epoxy-1-(p-ethylphenoxy)-3,7-dimethyl-2-octene (Stauffer R-20458) with insect juvenile hormone activity readily penetrated the puparium of white pharate pupae of Stomoxys calcitrans. The quantity and the persistence of the chemical in the puparium and in the developing pharate adult were determined over a 168 hr post-treatment period. The loss of chemical from the pharate stage was almost total within 168 hr, but over 20 per cent of the applied dose was still present in the puparium after the same interval.

The alkaline phosphatase activity of stable fly pharate pupae treated with 10 ng of an insect juvenile hormone analogue (JHA), Stauffer R-20458, or untreated pupae was rhythmic and peaked 48 and 96 hr after larval-pupal apolysis. Those treated with 10 μg were not rhythmic and peaked at 48 and 120 hr. Acid phosphatase activity showed a general increase throughout pupal-adult transformation and was three- to four-fold higher than alkaline phosphatase activity. At 24 and 48 hr after larval-pupal apolysis, acid phosphatase was lower in the treated animals, but at 72 and 120 hr, it was higher. Neither inhibition nor enhancement of acid and alkaline phosphatase activity or by three other JHAs could be demonstrated in vitro.