Some burying beetles such as N. vespilloides, N. orbicollis and N. defodiens are multi-brooded with the adults producing more than one set of young per year while others such as N. vespillo only produce one. The adult beetles both the flies eggs and larvae when ever they can but sometimes are forced to abandon a carcass if the number of fly maggots becomes too great. As I said in the introduction males being involved in the care of the young is extremely rare in the insect world. The factors which make this an evolutionarily successful practice for burying beetles relate to the nature of the main resource, i.e. the carcasses. Carcasses are a highly nutritious resource which occurs in an extremely variable and unpredictable pattern of distribution.
Carcasses are the limiting factor in burying beetle reproductive success.
In other words it is the number of available carcasses which controls the number of young a male or female burying beetles can produce during its life. When a carcass is found therefore, it is worthwhile doing everything possible to maximise the number of young you father or mother at that carcass. Also a lone parent is prone to having their efforts aborted by the arrival of another individual of the same species. An intruder of the opposite sex will kill off the existing young before initiating another brood, broods started like this are always smaller than the first brood because some of the resource of the carcass has already been used up. A larger member of the same sex will simply drive the holder off and take the resource for themselves.