Global Biotic Interactions is sort of an aggregator for organism interaction data. so that could be a good general reference. for example:
- https://www.globalbioticinteractions.org/?interactionType=interactsWith&sourceTaxon=Asclepias&targetTaxon=Insecta
- https://www.globalbioticinteractions.org/browse/?interactionType=interactsWith&resultType=json&sourceTaxon=Asclepias
however, there are other plant guides and specific papers that sometimes give a good list of this kind of thing. just depends on the plant and geography… are you interested specifically in milkweeds?