In 1909, the entomologist C. Emery noted that social parasites among insects (e.g., cleptoparasites) tend to be parasites of species or genera to which they are closely related. Over the years, this pattern has been recognized in many additional cases, and generalized to what is now known as Emery's Rule. The pattern is best known for various taxa of Hymenoptera, but also in members of other kingdoms such as fungi, red algae, and mistletoe. The significance and general relevance of this pattern is still a matter of some debate, as a great many exceptions exist, though a common explanation for the phenomenon when it occurs is that the parasites may have started as facultative parasites within the host species itself (such forms of intraspecific parasitism are well-known), but later became reproductively isolated and split off from the ancestral species, a form of sympatric speciation. Kleptoparasitism or cleptoparasitism (literally, parasitism by theft) is a form of feeding where one animal takes prey from another that has caught, killed, or otherwise prepared it, including stored food provisions, as in the case of cuckoo bees, which lay their eggs on the pollen masses made by other bees. ... Suborders Apocrita Symphyta Many families, see article Hymenoptera is one of the larger orders of Insects, comprising the sawflies, wasps, bees, and ants. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Red algae Classes Florideophyceae Bangiophyceae Cyanidiophyceae The red algae are a large group of mostly multicellular, marine algae, including many notable seaweeds. ... Families Santalaceae(Viscaceae) Loranthaceae Mistletoe is the common name for various parasitic plants of the families Santalaceae (in the section of the family formerly separated as Viscaceae) and Loranthaceae. ... Sympatry is one of three theoretical models for the phenomenon of speciation. ...