Dear Dammini

Could be A. craccivora based on the length of the Cauda and Cornicle (Cornicles longer than Cauda). Please check on this link i found it could be useful to a limited extent.

http://ucanr.edu/sites/CottonIPM/files/166555.pdf 

Regards,

Subramanian

Dear Subi,

Thanks for the information. I also thought that.

Dammini,

The apterae of both species can be easily distinguished as Aphis craccivora has a solid black dorsal abdominal patch contrary to Aphis fabae which has not. This is not evident on your photo and is best observed on slide-mounted specimens.

On this webpage you have keys to help you id aphids in herbaceous plants, shrubs and trees worldwide. You can start with "Key to Polyphagous Aphids" or the "Hot Lists and Keys" if you know the correct id of the host plant.

Best wishes,

Antonio

http://www.aphidsonworldsplants.info/

Dear Dammini,

There are 12-18 hairs on the cauda of both, apterous and alate females of Aphis fabae. However, in case of Aphis craccivora the number of bristles on cauda is only 4-9. Winter host of A. fabae in Europe are Evonymus europeus, E. verrucosus, Philadelphus coronarius and Viburnum opulus. As to A. craccivora, its eggs overwinter on perennial Fabaceae.   This was written by my late mentor, László Szalay-Marzsó, who the best aphid expert was earlier.  Our agricultural entomology textbooks use this information.  

Unfortunately, your photo is poor.

Dear Dammini,

The best identification tool for aphids is the work of Roger Blackman and Victor Eastop http://www.aphidsonworldsplants.info/

 is Aphis craccivora. But use the web site aphids on the world's plants 

http://www.aphidsonworldsplants.info/

Thank you very much for all your answers and suggestions. I will prepare the slides and try to identify.

Greetings,

You have to make a very clear slide to be able to see the taxonomic characters, and please  also see the following link.

http://influentialpoints.com/Gallery/Aphis_aphids.htm

I work with cowpea and I familiar enough with cowpea aphid Aphis craccivora. If I compare with pictures of black bean aphid, Aphis fabae, I found one of the differences between them is that cowpea aphid never having white markings on its dorsal abdomen. Aphid fabae having eight white marking on dorsal of its abdomen, each four white markings on left and right side.

Thanks.

Dammini