could have occurred in the early Pleistocene. In the case of E. meriana, there appears to be no obvious ecological factor that explains why the “flavescens” pattern occurs in 3 separate areas in the Neotropical region. Those in Brazil are almost identical to the ones in Nicaragua and El Salvador. Dressler suggests that E. meriana was once monomorphic with only the “flavescens” pattern, but has been replaced by the “bombiformis” patterns like its sister species E. bombiformis because it could be more superior as “warning coloration”. Sociality Mixed colonies in Apidae have rarely been recorded. Sometimes more than one species are observed in a nest, but this is more common in the bumble bees. Some scientists believe that parasites can be viewed as agents that promote sociality among bees in order to promote guarding behavior and cooperation in collective nest construction and maintenance. Roubik suggests that some advantages of colony establishment counters the evolution of eusociality. The mechanism of accepting other nest mates is unclear in E. meriana, but there is a capacity for joint nest maintenance and tolerance. This places limits on female sterility because there is no kin selection. Worker castes and non-reproductive females would not evolve if bees accept newcomers to the nest in order to offset costs of a small colony and risks from enemies. Polymorphism and social limits Eulaema show high polymorphism and high proportions of diploid males. After assays of 23 enzymes, Roubik focused on five polymorphic systems with six isozyme loci. E. Meriana had 35% heterozygotes for a HK loci, and 54% heterozygosity for the PGM loci. Diploid males were observed in rather high proportions. Diploid males were not observed to be larger than or more distinctive than haploid males, and responded to chemical baits in the same manner as haploid males. Homozygosity at the sex locus leads to 50% of the diploids being male in Hymenoptera, and diploid males are usually present at some stage of the life cycle. Euglossine polymorphism is almost twice that of bumblebees, stingless bees, and honey bees. Some scientists propose that euglossines lack the types of colonies formed by their relatives because of both high diploid male production and genetic polymorphism. Up to 50% of the bees that are intended to be females (diploids) would be males, therefore the supply of altruistic workers would not be stable. Without a stable supply of workers, colonies would not be