Unlike so many pests, which are content to trouble us only during a part of their existence, this twelve-spotted cuc.u.mber beetle is our enemy all its life long, for it spends its larval life eating the roots of corn and other field crops.

It is a wide-spread pest, with many relatives quite as bad as it is, and not only does it eat up the young and defenseless cuc.u.mbers and the roots of the corn, but it is the carrier of a germ infection of a serious nature to the cuc.u.mber. My friend, Dr. Erwin F. Smith, informs me that its kind has infested large areas in the South with this disease and dashed the hopes of thousands of boys who, instead of feasting on the melons they have planted with such care, must stand helplessly by and watch the leaves and flowers wilt and the vines decay. It must be remembered that this is a winged carrier of disease and anyone who still fails to understand the speed of travel of an epidemic had better watch the cuc.u.mber beetles busy spreading this destructive germ disease. A single beetle feeding on a diseased leaf can carry on its jaws enough germs to infect every melon or cuc.u.mber plant in a neighboring field, and that, too, in a single day.

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ONE OF THE SAWYERS

(_Monohammus t.i.tilator_, Fab.)

While standing on a street corner waiting for a street-car one day last summer my attention was attracted to this beautiful squirrel-gray creature at my feet. It was so evidently ill that, as I picked it up, I began to examine it to find out what was the matter. Cl.u.s.tered on its neck, out of reach of its feet or jaws were whitish bodies which evidently did not belong to its external skeleton but were probably the eggs of what I took to be some parasite whose growth within the body of the beast had brought about its pitiable condition. These are just visible between the creature's "horns" in the photograph. It was, in other words, a sick insect.

It is because biologists see these parasites so plainly all down through the scale of living things that they are so sceptical of accepting any other cause of human disease until all possibility has been excluded of its being caused by some parasite or other, too small to be seen even by using the best microscopes.

My sympathy for this long-horned beetle would be keener did I not read that its larval self is spent inside the wood of the pines and firs of our forests, doing great damage to them.

When one is puzzled to know why any living thing should be burdened by such antler-like antennae, let him remember the peac.o.c.k's tail and the bird of paradise's plumage and be content to know that the laws of evolution are not yet fully known, and that, given time and growth, almost any form can be evolved.

TWO-WINGED INSECTS

(_Diptera_)

Years ago in Berlin, my German landlady called me in as an expert to decide a controversy between her children and herself as to whether a frog had four legs or six. It seemed strange to me then that a grown-up woman should not know the number of a frog's legs. Yet there will be many who read these pages who do not know how many wings a fly has. And flies are much more important than frogs.

In fact the mosquito and the house fly, both included in the order of the flies, probably cause more deaths and are more dangerous to human life than any other creatures in the world.

These portraits are of a few only of the vast myriads of forms of two-winged insects which haunt the world. Were I to photograph just one individual of each different species which inhabit the globe, I would have to spend a lifetime doing it, and when it was finished it would make five hundred volumes about the size of this one.

There should never be the slightest difficulty in telling a fly from other insects for there are no other two-winged forms.

Although the flies are sucking insects, their beaks lap up liquid food and are not at all like the beaks of the bugs. In the great majority of flies, the beaks resemble a trunk with curious fleshy folds or lips. It is true some species, like the mosquito, have long, sharp-pointed stylets which, working up and down, puncture the skin of plants and animals.

The larval forms of many flies are maggots, those squirming, often almost headless creatures that abound in rotting carca.s.ses or decaying matter of all kinds, and this is one of the reasons why less is known about the flies than about some others of the insect world which have selected less revolting birthplaces.

Of course, in such a gigantic family no general rules apply, and still, a maggot, whether in an orange or a dead horse, is most likely to be the larva of a diptera or two-winged insect.

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THE CRANE FLY

(_Limn.o.bia sp._)

Every lover of the autumn woods must have noticed on some still October day, in the little clearings in the woods, these awkward, long-legged flies which, frightened by the approach of a human being, gather their ungainly hind legs together behind and their forelegs in front of them and slowly and laboriously flutter upward into the sunlight. They are well-named, these creatures, "the crane flies," for their legs are as long and apparently much more useless than those of the crane. In fact some entomologists have expressed themselves as wondering why they have such legs at all for they are so fragile that they break at the slightest touch.

They belong to a family with a thousand species in it and perhaps the most peculiar thing about them is that some forms of the family live and fly about when there is snow on the ground. This is a very rare exception in the insect world.

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AN INSECT HAWK: ONE OF THE ROBBER FLIES

(_Erax aestuans_, Linn.)

Her strong, spiny legs, her powerful body filled with strong wing muscles, and her sharp beak, make this robber fly one of the most dreaded enemies of the other winged insects for, like the hawk among the birds, she pounces on them in their flight and tears them to pieces with her beak, sucking the blood from them as she carries them in the air. A single one of these insect hawks, or robber flies, as they are called, has been known to catch and devour as many as eight moths in twenty minutes.

These robber flies are fearless creatures, for they attack and kill b.u.mble bees and wasps and even, it is said, that monster demon, the dragon-fly.

Tiger beetles, too, are said to fall a prey to this insect hawk.

Its other or larval self is also predaceous, boring into beetle larvae in the ground.

[Ill.u.s.tration]

A ROBBER FLY

(_Dasyllis grossa_, Fab.)

When I learned that this powerfully winged, hairy fly tears beetles' wings from off their backs with that wedge-shaped beak of hers, and sucks the blood of bees and wasps, it gave me a different idea of the great fly family, which hitherto I had thought was made up of defenseless creatures like the house fly.

Of all the insects we have photographed, few have seemed to be more thoroughly fearless or more ugly than the robber flies. I have never seen one capture and devour a creature larger than itself, but it must be as thrilling an adventure as to see a dragon-fly devour a gnat, or a spider pounce upon the prey entangled in its net.

[Ill.u.s.tration]

ANOTHER VIEW OF THE ROBBER FLY

(_Dasyllis grossa_, Fab.)

At first it looked as though this creature had two heads, one at each end of its body, but the great facet eyes, of which only one can be seen in the photograph, make it clear which is the head and which the egg-laying end of this strange, fearless robber of the air.

Just why it is called a robber fly when it really doesn't rob at all, but kills, is a mystery to me.

[Ill.u.s.tration]

ONE OF THE LARGE ROBBER FLIES

(_Mallophora sp._)

This robber fly is not so quick nor so savage as many of its family. It waits for some slow moving insect to come along then pounces upon it.

It probably breeds in decaying wood, although this is not certainly known, and it is very difficult to breed them artificially.

To the economic entomologist the ability to breed these monsters in captivity is one of the most important factors in studying out their life histories, as they are called, their various stages, the plants they feed on, their habits of moulting, of breeding and of feeding their young.