It is the Spanish fly, and the tincture is made of one part of dried Spanish flies and five parts of alcohol. Triturations are made of the powdered insect.

General action of Cantharis 

Peculiar eye symptoms
Objects look yellow.

Cantharis in facial erysipelas 
Erysipelas beginning on the dorsum of the nose and spreading to right cheek with the formation of large vesicles, which break and discharge an excoriating fluid.

Throat symptoms 
Burning from the mouth to the stomach ; throat highly inflamed and covered with plastic lymph ; spasm and intense constriction about the throat.

Cantharis in dysentery
Discharge of blood streaked mucus, looking like scrapings of the intestines ; cutting and burning in the anus ; the tenesmus of the bladder predominates over that of the intestines.

Urinary symptoms
Persistent and violent urging to urinate, with great tenesmus ; the urine is passed only in drops, and seems like molten lead passing through the urethra ; intense burning on urination, and aching in the small of the back.

Sexual symptoms 
Intense sexual excitement.
Gonorrhœa, with intense irritation and persistent erections ; the discharge is purulent and bloody ; useful when the disease has been sent to the bladder by injections.

Female symptoms
Nymphomania, with the bladder symptoms ; menses too black, too early, and too profuse ; it favors the expulsion of moles, hydatids, etc.

Skin 
It produces large blisters and bullæ, which are filled with an excoriating fluid, the skin burns like fire ; it is a useful remedy for burns and scalds when blebs form on a yellowish base.
In herpes zoster it is almost specific.