Meet Oxyrrhexis, a rare and fascinating genus of parasitoid wasps belonging to the family Ichneumonidae. These miniature assassins function as “koinobiont ectoparasitoids,” a scientific term for a truly sci-fi lifecycle: females lay their eggs directly on living cobweb spiders (Theridiidae). Incredibly, the spider continues its normal life and web-building activities while the wasp larva slowly feeds on it from the outside. Measuring between 3 and 8 millimeters, the adults exhibit massive size variation, which is entirely dictated by the size of the unfortunate host they were reared upon. I encountered this tiny wasp during my bicycle tour through northern Sweden. I initially mistook its delicate profile for a common sawfly, only to later realize I had crossed paths with a highly specialized, rare spider-hunter!