We have seen that certain forms, for example, the poisonous spiders, not only secrete a toxine in their poison glands, but that such a substance may be extracted from other parts of their body, or even their eggs. There are many insects which likewise possess a poisonous blood plasma. Such forms have been well designated by Taschenberg as _cryptotoxic_ (κρυπτοσ = hidden). We shall consider a few representative forms. [Illustration: 42_a_. Blister beetle.] [Illustration: 42_b_. An American blister beetle. Meloe angusticollis. Photograph by M. V. S.] THE BLISTER BEETLES--Foremost among the cryptotoxic insects are the _Meloidæ_ or "blister beetles," to which the well-known "Spanish fly" (fig. 42_a_), formerly very generally used in medical practice, belongs. The vescicating property is due to the presence in the blood plasma of a peculiar, volatile, crystalline substance known as _cantharidin_, which is especially abundant in the reproductive organs of the beetle. According to Kobert, the amount of this varies in different species from .4 or .5% to 2.57% of the dry weight of the beetle. While blister beetles have been especially used for external application, they are also at times used internally as a stimulant and a diuretic. The powder or extract was formerly much in vogue as an aphrodisiac, and formed the essential constituent of various philters, or "love powders". It is now known that its effects on the reproductive organs appear primarily after the kidneys have been affected to such an extent as to endanger life, and that many cases of fatal poison have been due to its ignorant use. There are many cases on record of poisoning and death due to internal use, and in some instances from merely external application. There are not rarely cases of poisoning of cattle from feeding on herbage bearing a large number of the beetles and authentic cases are known of human beings who have been poisoned by eating the flesh of such cattle. Kobert states that the beetles are not poisonous to birds but that the flesh of birds which have fed on them is poisonous to man, and that if the flesh of chickens or frogs which have fed on the cantharidin be fed to cats it causes in them the same symptoms as does the cantharidin. Treatment of cases of cantharidin poison is a matter for a skilled physician. Until he can be obtained, emetics should be administered and these should be followed by white of egg in water. Oils should be avoided, as they hasten the absorption of the poison. OTHER CRYPTOTOXIC INSECTS--Though the blister beetles are the best known of the insects with poisonous blood plasma, various others have been reported and we shall refer to a few of the best authenticated.