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I t is almost insoluble i n water but is soluble i n organic solvents, including propylene glycol. Wherever the term "wettable powder" is used it indicates a preparation of parathion a d ­ sorbed onto Attapulgus clay to represent the percentage indicated. " D u s t s " are prepared from the wettable powder b y further dilution with pyrophyllite. Experimental Acute Toxicity. T h e L D following oral administration of parathion, either i n propylene glycol solutions or i n aqueous suspensions of the 1 5 % wettable powder, has been determined for rats, mice, and guinea pigs.

Pigs, (Values in body of table represent number of deaths/number tested. Maximum observation period was 48 hours. /tnl. /Kg. 3 Method of Wilcoxon and Litchfield (il). Dermal Absorption. T o determine the t o x i c i t y of parathion following dermal application, the method of Draize, Woodard, and Calvery (3) was followed. Variables considered i n the design of these experiments were concentration as a factor of area, solvent, exposure time, and number of exposures. I n some cases the wettable powder was applied i n the dry form, while i n other cases sufficient water was added to produce a viscid paste.

7. M e a l worms. The three most common are the light meal worm, dark meal worm, and lesser meal worm. M a n y other insects are occasional casual invaders; the ones described are merely those most commonly seen. Ordinarily, when one or two specimens of an insect species invade a clean bakery, nothing is seen of them until they have bred and developed into a definite focus of subsequent infection; i n other words, until there is a colony i n the place where the original invader sought harborage.