Overlaying scans or screen captures of two maps is possible (you would add them to the same map, georeference them, and then adjust transparency). However, there is a better way.
Go to antmaps.org and check the about page. They have a data download option.
https://antmaps.org/about.html
https://antmaps.org/data/GABI_Data_Release1.0_18012020.zip
This zipfile contains a CSV file with the data observations, including taxon and lat/lon.
Add the GABI_Data_Release1.0_18012020.csv to your map in ArcGIS Pro.
Use the XY Table to Point tool to make a set of points of all of the observations in your project geodatabase.
Use the Select by Attributes tool to select one of the taxa you're interested in.
Those points will get highlighted in cyan.
Right-click the GABI_Data_Release1_XYTableToPoint layer and export the selected points to a new feature class in your project geodatabase.
Clear the selection and select the other taxon, then repeat the export process.
Now you have two layers of the two taxa of interest.
You could symbolize each layer with different symbols to display the overlap of observations.
The download also contains a polygon shapefile (Bentity2_shapefile_fullres). You could use these polygons to summarize the point data for each layer and display counts.
https://support.esri.com/en-us/knowledge-base/how-to-count-the-number-of-point-features-within-a-pol...
You could use the Point Density tool to map the density of the observations of each taxon and overlay those layers.
https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-analyst/understanding-density-analys...
You could use the Minimum Bounding Geometry tool with the Convex Hull option to make a polygon for each taxon.
https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/minimum-bounding-geometry.ht...
You could make a Heat Map of each layer.
You could identify hot and cold spots in the distribution of each layer.
https://learn.arcgis.com/en/projects/de-identify-health-data-for-visualization-and-sharing/
Best,
Bob
