bind9 caches wildcard responses

[Hans]

> As per RFC1034, responses for queries, which contain wildcard characters
> like (say,  *.mydomain.com), should not be cached.....
> but my caching server caches this response....is this a bug to bind9
> or in real time scenario...it does not matter...

Your server is not caching the wildcard record.
It is caching the actual request and that has no idee of this an wildcard 
record.
The actual request is blabla.mydomain.com and there is way to detect that 
this wildcard record.
Only the DNS servers known it is wildcard record or not.