The Black Belly of the Tarantula (1971) on Netflix

Plot summary

Maria Zani's husband Paolo interrupts her massage, saying he can prove she has been unfaithful; she denies it. That night a figure in black surgical gloves injects her with a chemical that keeps her awake but unable to move, then kills her. Tellini, the inspector on the case, questions Paolo and finds a photograph of Maria with a man's hand on her, half of it missing so the man cannot be identified. At home Tellini admits to his wife Anna that homicide work does not suit him. A clothing store owner with no link to Maria is killed next. Tellini traces the needles from the killings to a doctor who denies involvement, and Paolo, also claiming innocence, starts his own inquiry. A scientist shows Tellini how a wasp paralyzes a tarantula with a toxin and lays eggs in it.