When the queen bee lays her eggs, worker bees can determine whether the resulting larvae are to become an adult worker bee or an adult queen bee," Dr Hurd said.
The gunman killed his mother at the home they shared before driving to the school in her car and opening fire. Reports say the guns used in the attacks were registered to her.
Dr Boehlke thinks President Putin's is more emotional, with a sense of the weight of history and Russia's historic role as a power, compared with her pragmatic focus on economies.
They do seem to have the respectful relationship of old adversaries. In the past, they have not been warm and tactile with each other in the way, say, Mrs Merkel and US President Barack Obama were when he visited Berlin (before the revelation that his people were listening in on her phone). But that is not her way, or his.
