absolutely agree with Marisol

That agarose gel can give a lot of information about your RNA in a short amount of time.  You can see the integrity of the rRNA bands and can also visualize genomic DNA contamination up at very high mw.  I find the best results if I use DEPC water to make up the gel; it decreases the amount of degredation during the run compared to making up the buffer with regular dH2O.  I try to run 1ug RNA per lane to look for the 28S and 18S bands, have also seen 500ng work well.  Not sure how low you can go with the amount you load per lane, it looks as if you have a low starting amount.  Good luck. 

Kindly check if you have this equipment. You can have lot of information with just a microlitre of RNA. It gives information about the quality, integrity and also quantity of RNA. 

http://www.genomics.agilent.com/en/Bioanalyzer-DNA-RNA-Kits/RNA-Analysis-Kits/?cid=AG-PT-105&tabId=AG-PR-1172

Thank you all for your  answer Even if I run a regular agarose gel ( I mean, non denaturating gel) I can see the 28 & 18 S Bands?

I have realized as well, that I made a mistake when preserving the larvae in RNA Later.. I Thought it was just freeze them... and did not perform a 24 hs  at RT....  This can influence in RNA degradation? 

Dear Shambhuprasad : Regarding the KIT, I need a Tape station to check it.... right? 

 Dear Sarah Bacon: are you use DEPC water for both gel and TBE buffer ? do you think if i use more than  1ug RNA make smire ?

I have run 100ng RNA on TBE gel with ddH2O for 50 mins. I got good results for detecting integrity