> 2) is there any explanation or research on this? Mutt dogs are not more aggressive, why would bees.

Mutts are just random mixes. So-called hybrids are crosses between distinct lines, with the aim of producing heterosis (hybrid vigor). Heterosis has been observed in the bee. Ruttner writes:


Effect of heterosis and hybrid breeding

Experience so far available with crosses between bees of different geographical origins impressively confirms the results from other fields of breeding. The heterosis effect occurs in honeybees frequently, but not always, and is _never predictable_. 

Greater vitality and increased brood rearing and honey yield may be noted as positive results of crosses between races, and increased aggressiveness and swarming tendency as negative results. 

A pronounced effect of crossing is present only in the first generation. There is general agreement that the third generation of controlled crosses, and all uncontrolled crosses, are definitely inferior to the parental strains. This is why crosses have to be constantly established anew. 

Table 1 gives a summary of the results of some crosses between races and strains; in most of these the queens of the hybrid colonies were of pure race, mated to drones of another race, the workers thus being F1.


* He notes that these crosses were very aggressive:

mellifera x carnica
mellifera x (carnica x ligustica)

some of the crosses produced 200% or more honey compared to parents or baseline (mean).

F. Ruttner (1968) Methods of Breeding Honeybees: Intra-Racial Selection or
Inter-Racial Hybrids?, Bee World, 49:2, 66-72, DOI: 10.1080/0005772X.1968.11097194

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