http://rsbl.royalsocietypublishing.o...7-a8a03c101bd2

To quote from this scientific article detailing instances of parthenogenesis in pit vipers...

. In caenophidian snakes, a derived clade containing most of the extant species[18], FP results in the production of unusually small litters that are composed entirely of males with low offspring viability and large numbers of developmental failures [6,7,10].
We are actually both correct on the genders to a degree. MOST snake species produce all males during parthenogenesis (unless obligates), but apparently the boids like to produce all females.