1200 Hymenoptera in America North of Mexico 



pendently a number of times in all aculeate superfamilies. However, these biological distinctions 

 break down in most of the more primitive wasps belonging to the Bethyloidea and Scolioidea. 

 Many of these behave as true parasitoids in that the larval prey may be only temporarily para- 

 lyzed, occasionally several eggs may be laid on a single prey larva, and frequently no nest what- 

 ever is made, the prey being left in situ, or at most a crude cell may be constructed around the 

 subterranean prey as in most Tiphiidae and Scoliidae. Parasitism of the egg stage of the host is 

 known only among the Amiseginae (Chrysididae). Polyembryony is unknown, but parthenogene- 

 sis occurs in some Aculeata. Usually this is of the facultative kind as is found in social insects 

 such as some ants, vespid wasps and honeybees. It may be obligate in some aculeates, such as 

 the tiphiid wasp Methocha and some species of the bee genus Ceratina, where males are rare or 

 unknown. 



The simplest kind of nest among the aculeates is made by the wasp dragging the paralyzed 

 prey into a crevice in or above ground or back into the prey's burrow; the opening is usually 

 sealed off by particles of the substrate to make a crude cell. A second type of nest is also made 

 in a pre-existing cavity, such as borings of beetle larvae in wood or twigs, or in old insect galls or 

 abandoned mud cells. The nest in this second type may be unicellular as in the first kind of nest, 

 or it may consist of a linear series of cells, each cell separated from its neighbor by a partition of 

 mud, wood chips, resin, masticated plant leaves, or other substances. A third kind of nest is ex- 

 cavated by the wasp or bee in the ground, in rotten wood, or in the soft pith of such shrubs as 

 sumac and elderberry. The subterranean nests are frequently unicellular but multicellular nests 

 in the ground, rotten wood or pith may have the individual cells arranged in a linear series or in 

 clusters with the individual cells sealed by a partition or closing plug of the substrate. Occa- 

 sionally a mud turret may be constructed over the entrance of subterranean nests. Next, there 

 are the nests constructed entirely from foreign materials. Usually these are above ground 

 although some Vespidae and Bombinae have subterranean nests. The nests of solitary species 

 may be made of mud, or a mixture of resin and pebbles, with the cells arranged in parallel tubes, 

 or in clusters or with separate but adjacent cells; some exotic social Vespidae make a mud en- 

 velope around combs of hexagonal cells. A number of social species make paper or carton nests 

 in which the nesting material consists of masticated wood fibers, bark or rotten wood. Finally, 

 there is the complex nest of the honeybees constructed from wax secreted from glands in the 

 abdomen of workers. 



Aculeate larvae are normally cannibalistic if they come in contact accidentally. This tendency 

 is prevented in multicellular nests by the existence of partitions separating adjacent larvae. 

 However, some species make brood cells in which several larvae develop amicably without the 

 occurrence of cannibalism. Such nests have been reported for a few North American Isodontia 

 (Sphecidae) and Megachile (Megachilidae), and for many exotic Allodapini (Anthophoridae). 



True sociality (eusociality) has arisen independently several times in the higher aculeates, the 

 Formicoidea, Vespoidea, Sphecoidea and Apoidea. All of the ants are eusocial or are social 

 parasites of other ants, but the majority of wasps and bees are solitary species. Wilson (1971) 

 considers that eusocial insects must possess three traits: "individuals of the same species 

 cooperate in caring for the young; there is a reproductive division of labor, with more or less 

 sterile individuals working on behalf of fecund individuals; and there is an overlap of at least 

 two generations in life stages capable of contributing to colony labor, so that offspring assist 

 parents during some period of their life." Presocial insects exhibit one or two of the above traits. 

 Solitary species have none of these traits. 



Most solitary aculeates practice mass provisioning, that is, the egg is laid and a store of food is 

 placed in the cell with it, then the cell is closed; in many species the store of food is provided be- 

 fore oviposition. Some sphecoid wasps, such as many Bembicinae (Nyssonidae), have taken the 

 first step toward subsocial status by adopting progressive provisioning. This behavior is charac- 

 terized by placing the egg on a single prey specimen and not furnishing additional prey until the 

 egg has hatched or by the hatching of the egg before any food is provided; after hatching the 

 larva is fed daily or at intervals as required. Other aculeates, e.g., Moniaecera (Crabronidae), 

 some Andrena (Andrenidae) and Exomalopsis (Anthophoridae), have achieved the higher level 

 of communal status, in which several females use a common burrow entrance but presumably 

 maintain separate cells. A higher level of presocial behavior (quasisocial) is found rarely in some 

 exotic bees where two or more gravid females of the same generation cooperatively construct 

 and provision the cells. Some of our Halictidae have attained the semisocial stage which is 

 similar to the quasisocial except that unmated females of the same generation associate with a 



