This section is from the book "The Engineer's And Mechanic's Encyclopaedia", by Luke Hebert. Also available from Amazon: Engineer's And Mechanic's Encyclopaedia.
Insects vulgarly called Spanish flies: they are chiefly used on account of their vesicating or blistering properties. The insect is about two-thirds of an inch in length and one-fourth in breadth, oblong, and of a gold shining colour, with soft wing sheaths, marked with three longitudinal stripes, and covering brown membranous wings. The genuine cantharides are sometimes mixed with other insects of a square form, with black feet, which possess no vesicating property.
 
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