National Geographic : 1937 Jul
POTENT PERSONALITIES-WASPS AND HORNETS villain in the story, the cause of many tragedies. It was a cuckoo wasp (Plate VIII, upper left and top), looking for a chance to place an egg in one of the cells. The grub, emerging from its egg, would have fed upon the baby mud dauber, finally killing it. Many young mud daubers every year are victims of these cuckoo wasps. HOW THE BLUE BURGLAR ROBS A HOUSE Quite as callous as this jewel-like villain is another wasp, much like the yellow-legged mud dauber, but dark steel-blue in color the blue burglar (Plate IV, figure 15; Plate VIII, on bottom of cell mass at upper left). These steely-blue wasps are habitual housebreakers. After a yellow-legged mud dauber has built a cell, stocked it with food, and sealed it, one of these burglars comes along, breaks open the cell, throws out the spiders, and proceeds to make itself at home. It cleans out the cell, then stocks it with a new supply of spiders, laying an egg on the last one. Then it seals up the cell in a clumsy and amateurish manner. These wasps are common about puddles. But you never see them standing on their heads and digging up the mud. Instead, they fill themselves with water. This they use to moisten the mud of the cell so that they may break it open, and also to soften mud for use in sealing. Sometimes, instead of breaking into fresh cells, they use old ones from which the mud daubers have emerged. THE. MUD. DAUBERS' . TENANTS Old mud-wasp cells are much in demand, being used by a number of other wasps, some bees, and different kinds of insects. One of the wasps (Trypoxylon clavatum, Plate VIII, lower left), being much smaller than the mud dauber, makes two cells out of a single mud-wasp cell by means of a mud partition. Both sexes of this little wasp cooperate in home building. But the lady does all the heavy work. Her husband remains al most entirely within the cell. His duties, as he interprets them, are almost wholly supervisory. Another little wasp (Ancistrocerus unci natus, Plate VIII, right center) also uses as nurseries the abandoned cells of mud daubers, dividing each into three by mud partitions. In contrast to the others, this wasp stores the cells with caterpillars. A third wasp (Pseudagenia adjuncta, Plate VIII, upper right) finds these aban doned cells useful as hiding places for its own mud cells which it constructs within them, storing them with spiders. A few other kinds of wasps also use these cells. In addition, some of the mason bees (as Osmia cordata,Plate VIII, lower right) find these cells useful. They divide them into compartments, sometimes as many as five, by partitions of a waxy substance. They then plug the opening with wax. Besides the mud dauber many other wasps make cells of mud. One, the com mon pipe-organ wasp, constructs a num ber of parallel mud tubes, usually opening downward. After a tube is finished the inner end is packed with food, provided with an egg, and closed with a wall of mud. Then another section is provisioned and closed off in the same way, and the process is repeated until the tube is full, when an other tube is built beside the first (page 55). The most accomplished masons are cer tain small tropical social wasps (as Polybia fasciata) that build large and very hard mud nests in which even the delicate combs are made of earthenware. JUG-MAKERS FASHION GRACEFUL URNS The most artistically inclined of our com mon mason wasps are the potter wasps, or jug-makers. On slender twigs or grass stems they construct symmetrical little urns with a narrow neck expanding into a broad, thin, flangelike lip (Plate II, upper). After the jug is made, the mother wasp stores it with paralyzed caterpillars, then lays an egg, which is suspended from the top by a slender thread, like a pendulum, and seals it. The young one, after emerg ing from the egg, consumes the caterpillars. In winter you often see these little urns on the bare twigs, usually singly, sometimes two or even three together. Inside each urn is a plump grub, chilled and motionless -dead, apparently. But with the warmth of spring it revives and changes to a pupa. Later the pupa changes to a wasp that bites a hole in the side of its mud prison and comes forth (page 54 and Plate II, lower, female left, male lower center). Other wasps related to these jug-makers construct more or less elaborate apartment houses-for children only. These, too, are often seen in winter, when they seem to be nothing but irregular lumps of mud wrapped around a twig (Plate II, upper, right).