“Why is it so secret?” we asked.

“These little beetles,” the Major said, “are found only in one part of the Sudan. It’s an area of about twenty square miles, north of Khartoum, and that’s where the hashab tree grows. The leaves of the hashab tree are what the beetles feed on. Men spend their whole lives searching for these beetles. Beetle hunters, they are called. They are very sharp-eyed natives who know all there is to know about the haunts and habits of the tiny brutes. And when they catch them, they kill them and dry them in the sun and crunch them up into a fine powder. This powder is greatly prized among the natives, who usually keep it in small elaborately carved Beetle Boxes. A tribal chief will have his Beetle Box made of silver.”

“But this powder,” we said, “what do they do with it?”

“It’s not what they do with it,” the Major said. “It’s what it does to you. One tiny pinch of that powder is the most powerful aphrodisiac in the world.”

“The Spanish Fly!” someone shouted. “It’s the Spanish Fly!”

“Well, not quite,” the Major said, “but you’re on the right track. The common Spanish Fly is found in Spain and southern Italy. The one I’m talking about is the Sudanese Fly, and although it’s of the same family, it’s a different kettle of fish altogether. It is approximately ten times as powerful as the ordinary Spanish Fly. The reaction produced by the little Sudanese fellow is so incredibly vicious it is dangerous to use even in small doses.”

“But they do use it?”

“Oh God, yes. Every wog in Khartoum and northwards uses the old Beetle. White men, the ones who know about it, are inclined to leave it alone because it’s so damn dangerous.”

“Have you used it?” someone asked.

The Major looked up at the questioner and gave a little smile under his enormous moustache. “We’ll come to that in a moment or two, shall we?” he said.