Odd smoke formation in bomber stream. What is it ?

Found this picture online, and ... anyone know what the smoke trails crossing the aircraft contrails might be ? Rockets ? Flak of some kind ? The puffs hanging down at regular intervals is really odd to me.  I'm stumped.
 
 

I think they just contrails also, perhaps from fighter escorts.  It think these pictures have something similar, the  odd  "puffs" effect.   
 
http://www.fold3.com/image/#39014847
 
http://www.fold3.com/image/#37216269  and label
http://www.fold3.com/image/#37216309
 
I think this may be the same picture, only shown "right side" up.
http://www.fold3.com/image/#32442590
and the label:
http://www.fold3.com/image/#32442592
 
I think these contrails were  produced by water vapor in the engine exhaust (as opposed to the change in air pressure over the wings) and these were piston engines.   The exhaust would not be as "smooth/continuous" as a jet engine.  That may create the start of the "puff" effect which gets exaggerated as it disperses.  

Yes, contrails.  However, to me they look as though they are beyond the Fortresses -- you can see the newly formed contrails of the Forts overlay the contrails in question.  The contrails in question are dispersing as they have been in place for several minutes (or longer).