Map gene IDs to Ensembl gene ID
These are not gene ids, but groups of orthologous genes -- try to search for the ids on Google, I can find this page http://cegg.unige.ch/orthodb6/fasta.fasta?ogs=EOG6STSR2&amp;swaptree= and thus you should be able to download the sequences and ids from OrthoDB. 

Note that, strictly speaking, the are no Ensembl ids for Drosophila, only FlyBase ids that are also used by Ensembl.