Vermont. November 1, 2011. Sometimes nature just flies up and gets your attention. The wasp that flew up that day started sticking small round pieces of mud to the wall and then flew off. After a while it was clear that the wasp was building a nest of mud tubes on the outside wall of the house. It took three weeks to construct a matched set of five parallel tubes 5 inches long.
This mud dauber wasp, Sceliphron caementarium, is also called the black and yellow mud dauber or organ pipe mud dauber wasp. The legs of this slightly over sized 1 1/8 inch wasp are bright yellow and there is a yellow spot behind its head. It is a rather handsome looking insect and it is a hard worker. It takes a lot of mud and spiders to create a successful nest.
Each of the 5 tubes required as many as ninety flights carrying a ball of mud the size of half a pencil eraser to build the outside casing. Of the hundreds of loads of mud it successfully brought to the tubes it dropped just 2 onto the porch floor. The female used her mandibles to shape the round mud ball into rope like strands that were stuck onto the next oldest strand. This shaping caused a distinct buzzing sound coming from the rapid moving mouth parts. Once dry the mud becomes hard offering protection for the new generation of wasps that would grow in the tubes.
Although the wasps were never observed picking up their material there was road construction to replace two culverts close by, one site 150 yards and the other 200 yards from the house. Each construction site offered disturbed soils of the clay sand type used to construct the tubes. Water was readily available and the soil colors were different at each site, tan at one and clay green at the other. By observing the color of the forming tube you could tell which construction site was in use as the materials depot that day.
Each of the 5 parallel tubes (looking like ragged pipes for a church organ) was segmented inside into four chambers. A chamber was sealed off when the outside casing had reached the proper length. The whole structure housed 20 members of the new generation of wasps. Each chamber housed an egg laid by the female into which she inserted two spiders and then each chamber was sealed off from its neighbor not only between tubes but from other chambers in the same tube. The favored species of spider was the garden spider, Araneus diadematus.
In spite of the numerous times the wasp delivered spiders to the chambers, she did experience some problems initiating a soft landing with a spider in her grasp. The wasp seemed to overestimate her braking ability to deal with the extra momentum of the spider and would thump into the wall. On most occasions it was just an awkward landing, but other times the wasp would stun itself and would drift out of control down to the floor. It eventually always managed to deliver the spider to the tube.
Only the female can sting. She uses her venom to stun but not kill the spiders. In one chamber where the egg did not developed properly the spiders had not been touched by the larva. When examined several weeks after being put into the tube, the untouched spiders not only looked whole but actually moved their appendages in a dazed and uncontrolled manner. The wasp venom is long lasting but not deadly to the spider.
Wasp larva eating the spiders was terminal for the spiders. In those tubes with feeding larva the spiders were in various states of ingestion. The larva uses their mouth parts, shaped in some ways like the mouth of a Sea Lamprey, attached themselves to the spider’s abdomen and sucked out the juices of the spider.
As the larva mature they weave a silk, soft, transparent, reddish brown cocoon in the early stages of metamorphosis. As the larva matures the cocoon hardens to the consistency of a thin shelled capsule, darkens in color and becomes waterproof. The cocoon has a cylindrical shape 7/8 of an inch long and 1/4 inch in diameter and float quite nicely on water. The larva pupates over winter in the cocoon. The spring brings the final metamorphous in the life of the wasp. Its appearance once it breaks out of the cocoon and then the mud tube will be as a winged adult insect with handsome yellow legs.
Our wasp gave her young a secure container in which to undergo their life changes from egg to larva to winged insect. Nature has given this species a unique strategy and a work ethic to match it in order to meet their survival imperative. The mud tubes insure the next generation of wasps and the continuation of their species.
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David Deen is River Steward for the Connecticut River Watershed Council. CRWC has been a protector of the Connecticut River for more than half a century.