SAND, DIGGING, AND -MASON WASPS.

Otago Witness, Issue 2660, 8 March 1905, Page 84

SAND, DIGGING, AND - MASON WASPS.

By Dinorxts.

Sand, ov digging, wasps are found in all tropical, sub-tropical, and temperate parts of the world. Xew Zealand has few species, perhaps not more than two or three, the one presently under notice being a glossy black insect, with bluish sheen, long, ra-ther than broad 1 in build, the thorax or chest separated from the abdomen by the narrowly constricted "waist" imitated by deluded woman, but naturally established in the wasp tribe.

This fine insect (known to science as Pompilus monachus) is usually to be seen during the hottest days of summer, flying to and fro in the near vicinity of clay banks and cuttings. It is in such places, common enough in many parts of Otago, that the narrow tunnel forming the nursery of its young has been neatly excavated. It flies low, and often alights to hunt about on foot, keeping up, meanwhile, a perpetual loud buzzing with its wings, and vibrating its ant-ennse in a singularly energetic manner. This sound, even when the insect making it is invisible, strikes terror into the arachnid heai't of the most savage spider that hears it, no matter vhat its size. The encounter that follows can seldom be described as a fight. As a rule the terrified spidiar gives in without a struggle, is duly stung, and dragged ingloriously away "to form by-and-bye a living meal for th,3 nursling wasp in its dark cell in the cla,y bank. Though commonly designated as spider,killing flies, these insects are in reality genuine members of the great group which includes the wasps and bees, the subject of our present remarks being, in fact, a solitary wasp, one among some 700 forms known . to science throughout the world. These wasps are invariably handsome and 1 vigorous, but not usually showy insects with regard to colouration. They are distinguished in much greater degree by the peculiar methods they employ in providing for the start in life of their young. Long before men thought anything* about the subject, and probably long before man existed on this earth, this wasp had successfully mastered the art of keeping meat fresh for weeks or months, not for its own consumption, but for the nourishment of its young. "The. digging wasps seize caterpillars or spiders ; 'they paralyse or kill the victim by a sting, sometimes in the neighbourhood of the ventral nerve-cords, and 1 then carry it to their nest before laying their eggs, that their grubs when hatched may devour it" ("Insects: Their Structure and Life," by G. H. Carpenter.) It is to be noted that the larval wasp requir.es animal food, unlike the grub of the bee, which is fed upon pollen and honey ■The social wasps feed their larvas direct with shredded insects, etc.. andi in Britain and elsewhere these wasps commonly frequent slaughterhouses and butchers' shops tor the purpose of stealing fragments of meat to be used in feeding their grubs. lh& temale of the solitary wasp, instead lays up a store of live food enclosed along with one or more eggs in a clay cell, the number of cells made during a season depending partly upon the measure of success in the quest for prey, andi partly upon the numbpr of eggs produced. It is essential in the circumstances that the food should be fresh, and' this is adequately provided for by the prey being stung into insensibility, but cot killed. As Lord Avebury (Sir John Lubbock) says in his delightful little book, "On the Origin and Metamorphosis of Insects," in allusion to a kind of digging wasp that buries beetles with its eggs: "If the ceroeris were to kill tne beetle before placing it i n the cell it would, decay, and the young larva, when Hatched, would find only a mass of corrution. On the other hand, if the beetle were buried uninjured 1 , in its st rubles to escape it would be almost certain to°destrov the egg. The wasp has, however, the instinct of stinging its prey in the centre ot the nervous system, thus depiiving it of motion and, let us hope, of suffering but not oi life ; consequently, when the voun/? iaiva leaves tiv> egg. it finds ready a" sufficient store of wholesome food." In Darwin's "Journal During the Voyage ot M.xU.ts ; Beagle," the great naturalist gives an interesting account of an allied species, a Brazilian "mason wasp" : "Certain wasp-like insects, which construct in the corners of verandahs clay cells for their larvse, are very numerous in the neighbourhood of Rio. These cells they stuff full of half-dead spiders and caterpillars, which they seem wonderfully to know how to sting to that degree as to leave them paialy&ed, hut alive, until their ej»£s am

hatched ; and the larvae feed on the horrid mass of po-vrerkss, half-killed victims — a sight which has been described) by an enthusiastic naturalist as curious and pleasing ! I was much interested one day by watching a deadly contest between a Pepsis f.nd a large spider of the genus Lycosa. The wasp made a sudden dash at its prey, and then flew away. The spider was evidently wounded, for, trying to escape, it rolled clown a little slope, but had still strength sufficient to crawl into a thick tuft of grass. The wasp soon returned, and seemed surprised at not immediately fir.ding its victim. It then commenced as regular a hunt as ever hound did after fox ; making' short semicircular casts, and all the time rapidiy vibrating its wings and antennee. The spider, though well concealed, was soon discovered ; and the wasp, evidently still afraid of its adversary's jaws, after much manoeuvring, inflicted two stings on the under side of its thorax. At last, carefully examining with its antennae the now motionless spider, it proceeded to dsrag away the body. But I stopped both tyrant and prey-"

NEST OP THE NEW ZEALAND MASON WASP, with cocoons and remains of spiders upon which the larval wasp 3 ha-e fed. (After Sir Walter Buller.)

Both kinds of wasp are represented, each by one oi more species, in New Zealand, the nest here delineated having b°en taken from the woodwork of a house in Wellington. Some years ago, I received a similar one from a friend at Nelson. In this instance the nest had been built inside the .70oden lock of an outhouse. These nests are made of clay, which the wasp carries in little balls with, its feelers, all of the constructive work being done with skill and rapidity. Sometimes only a single row of cells is constructed, but the type of nest having two rows is very common. In parts of the North Island the mason wasp is occasionally so numerous as to be a nuisance. Sir Walter Buller mentions instances of a dozen or more nests having been destroyed in each of various houses, and how that the wasp will even commence building in ''the folds of tK cloth oi other similar article." He also mentions how a survey I" arty working a few miles inland were continually annoyed by the insects, three or four nests per day having been built in tbe spare garments of the party, or in the folds of the bag which held their bedding and provisions.

I have not heard of the mason wasp as being found about Otago, but the sand wasp is common, here, more so during some years than others. Last summer, my friend, Mr J. P. Maloney, Fortrose, sent me some fine cocoons containing insects just ready to emerge. While holding one of these to my ear, I could hear a faint sound inside, something between a rustle and a scratch, clearly denoting that the tenant was getting ready to quit. In a few minutes it had broken away a. segment of tbe casing and 1 showm its black, shiny head at the opening. In less than a minute it was out — a handsome and sturdy creature, black as coal, strong in limb and wing, and ready to tackle any spider up to or over three times its own bulk.

The depth to which our digging wasp extends its burrows probably varies considerably, but I am indebted to Mr W. B. M. Fea, the genial manager of Messrs W. Gregg and Co., Dunedin, for careful measurements made during a recent fishing excursion at the Waiau this summer. One burrow measured by Mr Fea had a depth of 18 inches, and was branched at the inner end. From the mouth there is a gentle slope upwards to minimise the risk of inundation; then a slight drop tcwards the bottom. When it is noted that the tunnel is as cleanly made as an augur-bore and nicely smoothed throughout, it seems amazing that a mere insect should prove capable of a piece of work so laborious 1 . Mr Fea observes- also that the actual work of excavating was done with the feet, much as the rabbit hollows out its retreat. It is interesting to compare here the method of the female sand wasp with tLat> of the larvae of our tiger beetles, which scoop out very similar dwellings, with their shovel-like heads, using the peculiar, hollow back to convey the debris to the opening.

With the. laudable desire no cloubt of doing well by its progeny, the sand wasp const antly^seeks for prey that is much too heavy to b<j borne upon the wing. Thus the habit of dragging its captives seems to have become fixed. A wasp wns seen by Mr Fca to drag a spider about three times its own size lor 20 feet along rough ground, then leave it and fly to its burrow 10 or 12 feet farther on. This practica of reconnoitring is habitual with these wasps .and with ichneumons, which make similar provision for their unborn young. On its return the wasp hawked about the spot for a little while, but soon found its senseless quarry and proceeded again to pull with a will. Arrived 1 at the burrow it entered "tail" first, as it had traversed the whole distance, only to find that ttie spicier was much bigger than the hole. However, confident in. its. own strength.

and in the belief that spideis are comliicssihle, it continued to tug until tba swollen abdomen of its captive slowly disappeared within the orifice

This was a good feat, and it is quite likely that a large proportion of the actual journey had been performed before the wasp and its prey were first obseived. Darwin, in the ''Voyage," quotes mention of another such instance in which a South American wasp of this kind was seen to drag a big spicier through tall grass, in a straight line to its nest, which was one 1-undred and sixty-three paces away. This wasp al&c made several tours of inspection before the end of its journey. Our mason wasp is also a veritable athlete, one mentioned by Captfin Gilbert Mair being seen by him "to fly to a paling fence, capture a' spider bigger than itself, drag it for a distance over the ground, and carry it up the side of a house and through an aperture to its nest. This nest, after several months building, was 16 inches long, threequarters of an inch in diameter, and contained twenty separate cells. Unfortunately, it was knocked down and broken, but the spiders were still alive, though nvmy of them had been imprisoned for months.

An African species of sand wasp which abounds at Zanzibar utilises cockroaches for larder-stocking purposes. Cockroaches, as everyone knows who has been in their company, are active and wideawake insects wherever found Th,e African one alluded to is no exception, but in presence of the s-md wasp it yields paralytically, and submits to be stung and carried off without making any resistance. Another congener of our sand wasps is named Pompilus formosus. It is a native of Texas, and the victim chosen as nourishment for its progeny is the immense Tarantula spider known as the bird-killer. This spider wasp, it has been observed, paralyses its huge victim with a single sting before proooeding to bury it in a nest dug out of the ground to the depth of five or six inches. It is probable that the poisonous acid injected by sand wasps has an antiseptic and preserving property. According to an African observer, caterpillars and lociists "retain their colour weeks after being stung, and this, too, in moist situations under a burning sun."

' A few words upon the life history of the sand wasp, and lam done. Insects, like all of the higher animals, are produced from eggs, but- it is not an insect that is born from an insect &gg. What is produced is a larva — a creature usually very far removed in structure and habifc from the thing it is destined to become later on. The larva of the sand, or mason, wasp is in fact as unlike its pcrents as well could be ; a whitish, legless maggot, or little better. In the larval stage all insects eat ravenously and grow nacre or less rapidly. As is well krown, it is only at this period of their existence that the most highly developed insects do grow, no increase in size taking place after the larval period is finished. Owing to some peculiarity in their mode of development, however, insect larvce cannot do much in the way of putting on bulk without- getting uncomfortably tight. Not- tight in the figurative sense, from alcoholic excess — though insects at anyrate often do get very drunk, — but so tight within their skins that until they burst and cast these oft' they must cease both to feed and to expand. Truth to tell, Nature seems to have been in a somewhat absent-minded mood when arranging the economy of insect organisation. Like the rest of its relations, then, the sand wasp larva indulges in carnivorous gluttony upon the spiders, flies, caterpillars, beetles, cockroaches, grasshoppers, and so on, according to species and locality, until it has cast several skins and been endowed with a succession of newones. By the time the larder has become bare the larva has become big in a ratio to correspond! with the amount of provender consumed. If it thinks about tha future it feels quite comfortable about it, as every well-fed person in similar circumstances should do. Like the average well-fed person, it too is in prime order for protracted slumber. Before going to sleep, as if conscious of possible visi : from fierce enemies in the shape of prowling tiger-beetles, and such like predatory eremies, it proceeds to weave a tough, silky sleeping-bag ; and in this liermetic-allv-sealed receptacle, protected also by the walls of the maternal cell, it promptly changes form, and becomes a pupa, or chrysalis. If it has had origin from an egg laid early in summer, this resting stage may not last more than a few weeks, but if it has been hatched late in summer, or in autumn, then the whole winter is passed in this condition of restful torpidity. But, though not a sign of movement may be visible outwaidly, wonderful changes are slowly taking place insidie the smooth, tight-fitting cocoon. The greedy grub that was has become a quite different-look-ing creature as a pupa, but the changes that follow are f-till more extraordinary. Through all the changing season, from the summer that was to the spring that is to be, the embryo wasp has lain snug and warm in the cunning retreat provided for it by a thoughtful mamma upon whom, its eyes never have and never may look with the juvenile fondness begat of cupboaid love. As the cold of winter gives way to the warmth of spring, strange dreams of a sunlit world of light and life come to the drowsing occupant of the dark, restricted cell. Visions of sappy spideis, fat caterpillars, and other tasty morsels hover, mayhap, before the as yet unseeing eyes of the hu.ect now rapidly approaching perfect metamorphosis. It is a strange thing this, calling up questions of origin, heredity, instinct, which we hnve not room to discuss at present. W.o know for certain that within its tight swathing al! the changes from larva to perfect wa^p have been consummated, and it is ready and: •eager for free life in the outer world 1 Not alone equipped with four beautiful wings and the other appanages of a nt-rfect

insect, but with all its wits about it also, the newly-evolvedi insect proceeds to gnaw its way out of both cocoon and earthy cell. It has never been taught anything, nor is it endowed with a nervous system likely to be of much service as a means towards the acquisition of knowledge. It has, however, inherited powerful instincts, and these serve to guide it towards the unerring exercise of those strange proclivities wheh we have already tad under scrutiny. Confident in those instincts, it passes from its nursing home, andi becomes at' once intent upon the active practice of those strange, uncanny habits of which it has been my task here to give iom? imperfect account.