  Kepler data from G-, K- and M-type stars are used to study conditions that
lead to superflares with energies above $10^{34} {\rm erg}$. From the 117,661
stars included, 380 show superflares with a total of 1690 such events. We study
whether parameters, like effective temperature or the rotation rate, have any
effect on the superflare occurrence rate or energy. With increasing effective
temperature we observe a decrease in the superflare rate, which is analogous to
the previous findings of a decrease in dynamo activity with increasing
effective temperature. For slowly rotating stars, we find a quadratic increase
of the mean occurrence rate with the rotation rate up to a critical point,
after which the rate decreases linearly. Motivated by standard dynamo theory,
we study the behavior of the relative starspot coverage, approximated as the
relative brightness variation. For faster rotating stars, an increased fraction
of stars shows higher spot coverage, which leads to higher superflare rates. A
turbulent dynamo is used to study the dependence of the Ohmic dissipation as a
proxy of the flare energy on the differential rotation or shear rate. The
resulting statistics of the dissipation energy as a function of dynamo number
is similar to the observed flare statistics as a function of the inverse Rossby
number and shows similarly strong fluctuations. This supports the idea that
superflares might well be possible for solar-type G stars.
