Insect guide > Wasps > Solitary Wasps

Solitary Wasps

To this group (Super-family Sphecoidea) belong nearly all of those insects which are known as the solitary wasps, in contradistinction to the social wasps which form communities and live in nests, usually constructed of a paper-like substance, and lead very much the same socialistic life which we see in the social bees. The solitary wasp, in the main, form burrows, just as do the solitary bees, construct cells within their burrows and in the cells provide food for their larvae. This food, however, is not the pollen and honey mixture which is found in the cells of the solitary bees, but it is other insects which have been stung and paralyzed by the mother wasp. To this super-family belongs a large assemblage of forms which comprise twelve large families, the habits of all being rather similar.

Nothing can be more fascinating than the study of the habits of the solitary wasps and no more readable book on a natural history topic was ever prepared, not even excepting the famous Natural History of Selbourne or the general volume of Kirby and Spence's Introduction, than that entitled, "On the Instincts and Habits of the Solitary Wasps", by George W. and Elizabeth G. Peckham, of Milwaukee, published as Bulletin No. 2 of the Wisconsin Geological and Natural History Survey.

The Peckhams, already noted for their interesting work on the habits of spiders, and attracted to the study of solitary wasps probably through observing these creatures carry off spiders to stow away in their cells for their young, have spent many summer days in close observation of these industrious, active and most intelligent creatures and have described their observations in the most charming style. They have entered into the lives of the solitary wasps and have shown them to be as interesting in their way as the much-more-written-about bees and ants. Their ingenuity in capturing their prey, the care with which they conceal their burrows, the differ- ent individuality among members of the same species, and more astonishing than all, the actual use of improvised tools by these creatures, and many other points which the Peckhams have brought out and described make one wish to drop all other occupations and immediately begin the study of the solitary wasps.

The active little wasps of the family Oxybelidae are known in Europe to burrow in the sand and to provision their nests with flies. European writers state that they do not paralyze the flies by stinging as with most other digger wasps, but that they crush the thorax just beneath the wings so as to destroy the great nerve ganglia at that spot. The Peckhams found one of our American species, Oxybelus quadrinotatus, burrowing in the sand and storing flies after the burrow was completed. There were sometimes a dozen flies in the same nest and all had the thorax crushed. This little wasp carries its prey by clasping the head of the victim with the third pair of legs, and flying thus, with the whole body of the fly sticking out behind her, she presents a remarkable appearance.

The wasps of the family Crabronidae are usually larger, but still are rather small insects. They burrow in sand and clay and many of them make their burrows in wood-in palings, posts, stumps and decaying logs. They store in their cells a great variety of insects. Xylocrabro (Crabro) stirpicola was found by the Peckhams to fill its cells with different kinds of flies. Others store spiders and plant lice. The interesting observation was made by the Peckhams on the species just mentioned that it works at night and that "her manners were an agreeable contrast to those of the wasps that we had been watching through the day. The feverish excitement of their ways seemed quite in keeping with the burning heat of noon, while Crabro's slow and gentle movements harmonized perfectly with the long shadows of evening." One specimen was seen to work industriously for forty-two hours, toiling from three in the afternoon on July 27, through that night and the day and night following until nine o'clock on the morning of the 29th. "Surely", say the Peckhams, "she takes the palm for industry, not only from other wasps but from the ant and bee as well." Her burrow was thirty-nine centimeters in length and was made in the stalk of a raspberry or blackberry.

The species which belong to the genus Trypoxylon and its close allies as a rule make use of the burrows of other in- sects. They sometimes store the insects which they collect in the deserted cells of a mud-dauber, and sometimes in the small round holes made by wood-boring beetles in old trees. Many of the species seem to store up plant lice but others capture and paralyze different kinds of spiders. There is a very important wasp which belongs to this group which does not occur in the United States but which I am trying to introduce.

This is the Ampulex which preys upon cockroaches. Perkins, quoted by Sharp, says that in West Africa cockroaches are stung by these wasps and placed in confinement in some such spot as a keyhole and in one case one was apparently prevented from afterward escaping by the wasp carrying some heavy nails into the keyhole. Rothney, also quoted by Sharp, says, "I saw two or three of these wasps (A ruficornis) collar a peculiar cockroach by the antennae and lead it off into a crack in the bark, but as the cockroach reappeared smiling each time I don't know what was up."

The genus Ammophila contains some of the most interesting forms in this family, and the habits of one or more species have been described in the most interesting way by the Peckhams, by the late William Hamilton Gibson, and Dr. S. W. Williston, and by Mr. Theodore Pergande. These are the insects which use tools. Their burrows are deep in the earth and are carefully concealed by the insertion of a stone, over which dry earth is scraped.
When the female returns with a caterpillar, (and she travels unerringly to this concealed burrow for a long distance,) the earth and stone are removed, the caterpillar is carried down into the burrow and the mouth is once more concealed until another caterpillar is brought. The solicitude exhibited by the maternal wasp for fear her burrow may be discovered has been vividly described by all of the authors above mentioned. When the burrow is complete the female wasp has been observed to use a stone as a tamping iron to pack the earth into the mouth of the burrow. This is the tool use referred to. Dr. Williston states that he feared to publish his observation at first, since he might not be believed. Pergande noticed that after the burrow was completed and filled the mother wasp revisited the spot occasionally to satisfy herself that everything was secure against intruders and to make surety doubly sure by placing additional disguising objects over the already disguised burrow mouth.

It was in their study of one of the Ammophilas that the Peckhams noticed a very distinct personality among the females which they watched at work. This personality was not of individual appearance but of such mental attributes as careful painstakingly carelessness and industry or laziness. One seemed to hurry tremendously and spent no time on non-essentials. Another was an artist, working for a long time on the closing of her burrow, arranging the surface with scrupulous care and sweeping away every particle of dust to a distance. Still another went to the extreme in carelessness, carrying the caterpillar in a very careless way and making a nest which was a very poor affair. Still a fourth was "the most fastidious and perfect little worker of the whole season, so nice was she in her adaptation of means to ends, so busy and contented in her labor of love, and so pretty in her pride of her completed work." In fact, they seem to have almost as much individuality as human beings and the result of these observations has a strong bearing on the discussion of instinct.

Fabre, the French entomologist, who studied the same insects, considered that they were inspired by autonnatically perfect instincts which can never have varied to any appreciable extent from the beginning of time. Deviation from the regular rule, he thought, would mean extinction. The Milwaukee authorities, however, found that variability was the one unmistakable and ever present fact, and this variability existed in every particular, in the shape of the nest and in the manner of digging it, whether it is left closed or open, in the manner of stinging the prey and of crushing it, in the manner of carrying the victim, in the way of closing the nest and in the condition produced in the victim by the stinging, some dying and others living for a long time, though nearly motionless. All this variability the Peckhams got from the study of nine wasps and fifteen caterpillars ! The mud-daubers of the genus Sceliphron (formerly and in most books placed in the genus Pelopaeus) are among the most interesting members of this super-family. They build their nests of plain mud in sheltered places under the eaves of barns or even in the attics of houses. The food supply with which the cells are stored consists almost invariably of spiders, as many spiders being packed into one cell as the cell will hold. A single egg is laid upon the last spider packed in and the larva eats rapidly, consuming the abdomen of the spiders first and subsequently the rest of their bodies, eating both dead and living spiders. After the egg is laid and the nest closed up new cells are constructed by the same female.

A curious observation has been made by Schwarz in the Washington parks and gardens. He found that one of the Sphegid wasps - Chalybion coeruleum - was engaged in capturing a certain kind of spider which hid itself so carefully that it was most difficult to find. Instead of spending her time in fruitless searching the wasp would entangle herself in the web of the spider when the latter would immediately dart out from her hiding place, thus exposing herself to the wasp who would easily free herself from the web and chase the spider to its retreat.