It was an insect fully fifteen feet in height, three times that of a beetle, lurking among the fungi. He saw a hugely elongated neck, a three-cornered head with a pair of tentacles, and two pairs of legs as long as a giraffe's. But what gave the added touch of horror was that the monster, balancing itself on its hind legs, had its forelegs extended in the attitude of one holding a prayer-book! That attitude of devotion was so terrible that Tommy uttered a wild cry of terror. At the same time another cry broke from Dodd's lips. "God, a praying mantis!" he shouted, struggling madly to push off his shell and Haidia's. The next moment, as if shot from a catapult, the hideous monster launched itself into the air straight toward them. (_To be concluded in the February Number._) The Cave of Horror _By Captain S. P. Meek_ [Illustration: "_Suddenly, for no apparent reason at all, one of the men on guard was jerked into the air feet upwards._"] [Sidenote: Screaming, the guardsman was jerked through the air. An unearthly screech rang through the cavern. The unseen horror of Mammoth Cave had struck again.] Dr. Bird looked up impatiently as the door of his private laboratory in the Bureau of Standards swung open, but the frown on his face changed to a smile as he saw the form of Operative Carnes of the United States Secret Service framed in the doorway. "Hello, Carnes," he called cheerfully. "Take a seat and make yourself at home for a few minutes. I'll be with you as soon as I finish getting this weight." Carnes sat on the edge of a bench and watched with admiration the long nervous hands and the slim tapering fingers of the famous scientist. Dr. Bird stood well over six feet and weighed two hundred and six pounds stripped: his massive shoulders and heavy shock of unruly black hair combined to give him the appearance of a prize-fighter--until one looked at his hands. Acid stains and scars could not hide the beauty of those mobile hands, the hands of an artist and a dreamer. An artist Dr. Bird was, albeit his artistry expressed itself in the most delicate and complicated experiments in the realms of pure and applied science that the world has ever seen, rather than in the commoner forms of art. The doctor finished his task of weighing a porcelain crucible, set it carefully into a dessicator, and turned to his friend. "What's on your mind, Carnes?" he asked. "You look worried. Is there another counterfeit on the market?" The operative shook his head. "Have you been reading those stories that the papers have been carrying about Mammoth Cave?" he asked. Dr. Bird emitted a snort of disgust. "I read the first one of them part way through on the strength of its being an Associated Press dispatch," he replied, "but that was enough. It didn't exactly impress me with its veracity, and, from a viewpoint of literature, the thing was impossible. I have no time to pore over the lucubrations of an inspired press agent."