This README file refers to the data reported in manuscript FE-2017-00991.R1 published in FUNCTIONAL ECOLOGY. Authors: Corinne Hertäg & Christoph Vorburger Title: Defensive symbionts mediate species coexistence in phytophagous insects The study design is explained in the publication. For queries please contact christoph.vorburger@eawag.ch. The file 'aphid_and_mummy_counts_for_DRYAD.txt' contains counts of two competing aphid species and counts of parasitized aphids from each species (mummies) on plants harvested from caged experimental populations. The file has 12 columns: treat: Experimental treatment. 8 different treatments.The treatments correspond to combinations of the three factors reg_a, reg_m and parasitoid (each either present or absent) in all possible combinations (factorial experiment) block: Experimental block. cage: Unique identifier for each caged population. Corresponds to one replicate in the experiment. reg_a: Regiella infection in Aphis fabae: present or absent. reg_m: Regiella infection in Myzus persicae: present or absent. parasitoid: Factor describing whether the aphid parasitoid Aphidius colemani was contained in the experimental cages: present or absent. day: Time (in days) when plant was harvested and the insects counted. The first count marks day 0 of the experiment. plant_cm: Stem length of the harvested plant on which aphids and mummies were counted. aphis: Number of Aphis fabae individuals (all life stages) counted on the harvested plants. a_mum: Number of Aphis fabae mummies counted on the harvested plants (only for treatments with parasitoids). myzus: Number of Myzus persicae individuals (all life stages) counted on the harvested plants. m_mum: Number of Myzus persicae mummies counted on the harvested plants (only for treatments with parasitoids).