1741 



Superfamily APOIDEA 



By Paul D. Hurd, Jr. 



This superfamily contains the bees which, like many other aculeates, visit flowers for nectar. 

 However, unhke nearly all other aculeates, the bees and most wasps of the Masaridae provide or 

 feed their larvae with a mixture of pollen and nectar or, in some bees, the mixture is converted 

 into glandular substances which are then fed to their larvae as well as to certain adults. It is 

 presumed by many specialists that bees as a group evolved from flower-visiting wasps, most 

 likely the sphecoid wasps (but possibly also other groups of aculeate wasps), by developing a de- 

 pendence for food upon pollen and nectar (and sometimes other substances, such as plant oils) 

 and thereby have abandoned the habit of provisioning their nests with insect or spider prey. It 

 is not known when this dependency arose, but it could not have occurred before the advent of 

 Angiosperms which did not begin to flourish until the latter half of the Cretaceous period and 

 which then became the dominant flora of the earth by the Tertiary. In general, the evolution of 

 the entomophilous flower has resulted in the replacement of a shallow, flat or bowl-shaped 

 flower by a corolla-tube. The progressive increase in the depth of the corolla-tube conceivably 

 has resulted from coevolutionary interactions between the flowers and entomophilous insects, 

 especially bees, with progressively more elongated mouthparts. Although the earliest known 

 fossils of bees (Tertiary) are insufficient to establish ancestral relationships with other aculeates 

 or to demonstrate that the evolution of mouthparts proceeded from the short to the 

 long-tongued condition, it is probably significant that this sequence is being corroborated by stu- 

 dies on the systematics, morphology, biology, behavior and biogeography of the contemporary 

 bee fauna of the world. This fauna is at present considered to consist of eight famihes which in 

 most current classifications are usually arranged phylogenetically as follows: Colletidae, Ox- 

 aeidae, Andrenidae, Hahctidae, Melittidae, Megachihdae (including the Fideliinae), 

 Anthophoridae and Apidae. Even though there is some and sometimes much variation in the 

 length of the glossa within each of these families, the first five families listed above contain the 

 so-called short-tongued bees while the remaining families consist of the so-called long-tongued 

 bees. Although the short-tongued bees of only three families (Colletidae, Melittidae and Halic- 

 tidae) are present on all continents, only the Colletidae are exceptionally diverse and 

 well-represented on the southern continents, especially in Australia where other presumably an- 

 cient groups of plants and animals survive today. The glossa of the Colletidae, in addition to 

 being normally short and bilobed, is also usually truncate and bifid and therefore is more 

 wasp-like in structure than is the glossa of any other family of bees. Thus it is believed that the 

 initial evolution of bees resulted in the development of short-tongued bees which radiated 

 throughout the earth and this event was subsequently followed by the coevolution of the corol- 

 la-tube and the long-tongued bees which also have spread throughout the world. Consequently, 

 the Colletidae are regarded by most speciaHsts as representing the most primitive group of liv- 

 ing bees. Most, but not all, authors believe that the Apoidea represent a monophyletic assem- 



