Short story with crab-like aliens who inhabit humanoid robots to study earth

Question

Pretty sure this is a short story, where a crab-like alien comes to Earth in a humanoid robot. He meets a regular human woman, but also finds another fellow crab-like (who he catches during feeding time).

Answer 1

"The Reality Trip", a novelette by Robert Silverberg, first published in If, May-June 1970, available at the Internet Archive. You may have read it in one of these compilations. I found it in the anthology Aliens Among Us edited by Jack Dann and Gardner Dozois.

Alien on Earth meets human woman:

I am a redemption project for her. She lives on my floor of the hotel, a dozen rooms down the hall: a lady poet, private income. No, that makes her sound too old, a middle-aged eccentric. Actually she is no more than thirty. Taller than I am, with long kinky brown hair and a sharp, bony nose that has a bump on the bridge. Eyes are very glossy. A studied raggedness about her dress — carefully chosen shabby clothes. I am in no position really to judge the sexual attractiveness of Earthfolk but I gather from remarks made by men living here that she is not considered good-looking. I pass her often on my way to my room. She smiles fiercely at me. Saying to herself, no doubt. You poor lonely man. Let me help you bear the burden of your unhappy life. Let me show you the meaning of love, for I, too, know what it is like to be alone. . .

He reveals his crab-like body inside the humanoid robot:

I push myself forward, stepping between the levers and struts, emerging halfway from the human shell I wear. I have not been this far out of it since the day they sealed me in, on Homeworld, I let her see my gleaming carapace. I wave my eyestalks around. I allow some of my claws to show.

"See? See? Big black crab from outer space. That's what you love, Elizabeth. That's what I am. David Knecht's just a costume and this is what's inside it." I have gone insane. "You want reality? Here's reality, Elizabeth. What good is the Knecht body to you? It's a fraud. It's a machine. Come on, come closer. Do you want to kiss me? Should I get on you and make love?"

He meets a fellow alien:

To sidestep prolonged conversation and possible entanglement I get off the elevator one floor below the right one. Let her think I'm visiting a friend. Or a mistress. I walk slowly down the hall to the stairs, using up time, waiting so she will be in her room before I go up. A maid bustles by me. She thrusts her key into a door on the left: a rare faux pas for the usually competent help here, she forgets to knock before going in to make up the room. The door opens and the occupant, inside, stands revealed. A stocky, muscular man, naked to the waist.

"Oh, excuse me," the maid gasps and backs out, shutting the door.

But I have seen. My eyes are quick. The hairy chest is split, a dark gash three inches wide and some eleven inches long, beginning between the nipples and going past the navel. Visible within is the black shiny surface of a Homeworld carapace. My countryman, opening up for Second Feeding.