SCHOOL IN THE OPEN

Star (Christchurch), Issue 18615, 17 November 1928, Page 20 (Supplement)

SCHOOL IN THE OPEN

STUDIES IN THE GREAT OUT-OF-DOORS

(By

J. J. S. Cornes,

8.A., B-Sc.)

The “Star” has arranged with Mr J. J. S. Cornes. 8.A., B.Sc., to write a series of illustrated articles which will give teachers and others a fuller appreciation of the Great Out-of-doors. They will deal with various aspects of plant and animal life, as well as with inanimate nature. Questions and material for identification will be welcomed.

THE TIGER BEETLE. CCLVI. Many of the larvae (grubs) of beetles live on grass-roots or on wood, even though the adult is to be carnivorous. But there is a very common beetle throughout New Zealand, and with closely-related Species in far-away England, whose grub, like itself, is the tiger among the smaller insect peoples. On fairly dry clay or heavy soil banks you have surely seen many little round holes, not much above an eighth of an inch in diameter. Each opens into a horizontal tunnel, some six to nine inches in, where lives and lurks the “Penny Doctor,” or “Butcher” grub, the larva of the Tiger Beetle.

Suppose you are walking from the “Takahe” to the “Kiwi,” and step off the road to examine some of these holes in the bank. You may see no occupants, for the grubs have felt through the soil the vibration of your footfall, and have retreated deep into their caves. Yet, if you look carefully, you may detect the metallic violetpurple sheen of a head some half-inch You wait and (if it is a sunny day, at least) heads soon appear, level with the mouths of the tunnels. These steelylustrous heads fill up one-half of the openings:; the upper semi-circle is tilled by a fiat, soil-coloured, because soilcovered, crown on the first segment, which is greatly flattened and sharply kinked behind to bring it verticle. You bring a grass-stalk near the mouth of the burrow. With lightning swiftness the grub darts out on it, grasping it with sickle-shaped mandibles. Far into the darkness of the cavern the grub draws the straw, imagining that it has some tasty insect. Even when you begin to drag the strawout again it may hold on, and allow itself to be quite withdrawn from its retreat.

What a strange, Z-shaped, fat, yellowgrub it is! It has three well-developed pairs of pointed legs on the thorax—these are foundations for the long legs of the adult beetle—but. as with other beetle larvae, or grubs, there are no fleshy', blunt, hook-fringed pro-legs on the abdominal segments, as in caterpillars.

Midway down the abdomen, on the fourth segment behind the legs, and what appears the fifth from the end. there is a hump or tubercle on the back, deeply cleft by a groove into two mounds. On each mound are two curved, forward-directed hooks, one much larger than the other. When the grub, lying in wait at the cave-mouth, darts suddenly forward upon its prey, these hooks, catch in the ceiling and prevent it from over-reach-ing itself. In this they are assisted bya lintel above the door, for the shaft narrow's suddenly'- at the entrance (as you see if you cut away a quarter of an inch of the soil), and the hump catches in this. In any case, the hump with its spines must give a good leverage when the larva is pulling an insect along its burrow. But it also demands that the shaft be dug of greater dia meter than the body, to allow of rapid movement.

It is said that the grub digs its cave by carrying the soil out on the flat shield crowning the first segment, and tipping it over tHe bank. At any rate, this rimmed shovel is mud-covered, and helps to camouflage the head. When about to pupate, before becoming motionless while going through the wonderful transformation from grub to winged insect, the larva creeps to within one or two inches of the mouth of the burrow. There the body shortens, and soon all the future appendages can be clearly seen. For the beetle-pupa, unlike that of a moth, has no hard skin on the outside to hide, or at the most suggest by its ridges and grooves, the limbs tightly sealed down within. Here there is but the thinnest of gauzy veils, and even this is tucked closely into all the angles and tightly wrapped about all the limbs. The pupa is delicately and beautifully made —its legs, antennae, mandibles and wings are almost transparent, as if moulded with wonderful skill from glass. To hold it still and unharmed—for it is extremely tender—against the smooth

sides of the shaft, there are three rows of spines, one down the back, and one down each side. Thus, with head turned toward the door near-by, the pupa awaits its awakening. There are few beetles about yet, but the pupae already formed will be emerging any day now. Nearer Christmas there are great numbers of pupae in the tunnels, and many beetles on the banks and in the gutters. You surely know the beetle. On hot, dusty’ paths through tea-tree, or along the gutters and banks of hot country roads, they fly and run before you in friendly’ company, wasting no time on that preliminary unpacking and unfolding of the lower wings which is so characteristic of most beetles. The beetle, like the larva, lives on other insects, and is a greater hunter, now that he can choose his hunting ground. As we mentioned when describing the large Huhu beetle, a peculiarity of beetle-structure is that the upper, or front, wings are not used for flight, but as horny cases to protect the delicate flight-wings below. These hard “elytra” meet down the middle line, without overlapping. Next time you catch a Tiger Beetle, be sure you admire the beauty’ of its markings, especially’ of the unsuspected row of blue-green metallic buttons down the inner edge of each of the elytra. Children get much fun from observing the movement of the grub, and this becomes an intelligent interest when the many adaptations of structure to function are understood. In the North Island the children push straws down the tunnels, many’ of which are vertical, in the hard soil of paths. The grub, apparently regarding the straw as so much rubbish (compare its attitude toward a straw held in front of the burrow), pushes it upward. Seeing it move, the children, by' pulling gently, get the “penny doctor” right out. This species is Cicindela tuberculata. Here the common species, Cicindela latecincta, does not seem to hold as tenaciously as the northern one. But y’ou can get the larva thtis: Approach the bank softly; soon heads will appear. With a sheath knife make a quick, sloping stab from below upward, so as to cut off the

grub’s retreat, and lever out the piece or soil containing it. From other holes where no heads appear you may get pupae. (To be continued next Saturday.)