Summertime is the best time to view and learn more about the fascinating creatures we call “bugs”. Stroll around your neighborhood or school yard and take a “safari”, you are bound to discover multitudes of these “misunderstood minibeasts”; the Arthropods. In order to appreciate them better, you will probably want to know a little bit more about them, and whether or not they could possibly be harmful.
- So, then, what are they? Invertebrates are the animals without backbones and are the largest group of animals in the world. They include groups such as annelids (segmented worms), mollusks (snails and slugs, clams, octopus, etc.), echinoderms (sea stars & sea urchins), and arthropods (insects, arachnids, millipedes, centipedes, and crustaceans).
Arthropods are the most extensive phylum in the animal kingdom, composed of more than three fourths of all known species. There are approximately 900,000 species of arthropods that have been recorded, and many more remain yet to be classified. Arthropods are more widely distributed throughout all regions of the earth than are members of any other phylum. They are found in all environments, from ocean depths to very high altitudes, and from the tropics to both polar regions. Arthropods have adapted to survive on land, in the air, and in fresh, brackish and marine waters.
All arthropods have:
- an exoskeleton (skeleton on the outside)
- jointed legs
The arthropods have five main classes:
Many people classify these critters into two groups: “good” and “bad”. Some people will generalize all of them as just “bugs”. Every one of these animals, though, is an integral part in the web of life and serves its purpose appropriately.
The insects are the largest group of of the arthropods. In fact, they are the largest group of animals in the world. With the exception of the ocean, insects have adapted to live in almost every type of habitat and niche. All insects have six legs, three body parts (head, thorax and abdomen), and one pair of antennae in their adult stage. There are approximately 1 million species of insects in the world, and many more are continuously being discovered.
O.K., now, face it. For many people, just the mention of “bugs” conjures terror and trepidation invoking images of a Steven King novel or a horror movie. But insects and their relatives are some of the most vital animals on Earth! Without them, our blossoms would never be pollinated and we would have no bounties of fruits or vegetables. Many species of birds, fish, reptiles, amphibians, and mammals (including humans in many countries) devour them with relish (and maybe a little catsup, too).
Insects can be our best friends or our worst exasperation. We have all had our share of annoyance with aphids, ants and other abominable, diminutive animals. But, how many times have we been awed at these same ants scurrying to and fro as though their lives depended on this apparent chaos? Or the bees skipping from blossom to blossom with their buzzing filling our ears with this sound of a summer day? How often have we marveled at the butterfly emerging from its chrysalis and taking flight in its endeavor to add additional colors to our existing palette of flowers? Who has never taken the opportunity to relax in the yard and watch the butterflies flutter and frolic. Who has never delighted in sounds of the chirping crickets or, (in some parts of the country), has not been thrilled at the fabulous “fireworks” display of the firefly on a warm, balmy summer evening. How can it be that we hold some of these creatures so dear, and yet are so repulsed by others that we are sometimes tempted to drench the entire piece of land in poisons to rid it of a few “miscreants”.
Many insects are very beneficial. We are all familiar with the ravenous appetite of the Aphid-craving Ladybird Beetle and the super pollination occupation of the Honey Bee. But, they aren’t our only useful allies. Other helpful insects include: Trichogramma Wasps which parasitize caterpillar eggs; lacewing larvae that devour aphids, mealybugs, scales, whiteflies, insect eggs, and mites; and Preying Mantises who consume many, many pests.
Others, though not exactly “beneficial,” aren’t really harmful either. A good example of this is the Green Fig Beetle, also called the Green Peach Beetle. Sometimes mistaken for the destructive Japanese Beetle, to which it is related, this innocent beauty only feeds on over-ripe and rotting fruit. In return, he gives us the pleasure of delighting in his iridescent emerald green body and deep green velvet wings. The larvae (grub) of this same beetle is commonly found in our compost heaps (he’s the big, fat whitish “C”-shaped “worm” with the brown head). As “ugly” as some people deem him to be, he really is quite the helper. He assists with decomposition by digesting the compost, and his feces add nutrients to the pile.
Another common garden insect, one for whom I get many inquiring phone calls, is the Jerusalem Cricket. Many people call him “Potato Bug” and in Mexico, (where he is mistakenly considered to be deadly) he is called “Niño de la Tierra, or “Child of the Earth”.
He is neither a potato, nor a bug, nor is he deadly. He is, however a large (about 2-2-1/2″) insect, golden-brown in color with a bald head, and he does possess fierce looking mandibles that can inflict a painful bite if handled. Most humans, though, by virtue of his handsome countenance, have no desire to pick him up. Unfortunately, also because of his looks, he has often found the bottom of many a shoe. Ferocious features aside, he is a harmless scavenger.
The Arachnids include the spiders, scorpions, ticks and mites. Arachnids have eight legs and two body parts; the cephalothorax and the abdomen. They have no antennae.
Many arachnids are venomous, but only a small percent of the venomous species are dangerous to humans. The group of large spiders that we refer to as “tarantulas” are not considered to be dangerous! Their venom is usually only toxic enough to kill small prey. The bite would definitely be painful, but it would not be fatal. The only potentially dangerous spiders we have in California is the Black Widow and the Violin Spider, which have caused some human fatalities. Even then, the lethal bites made up only a small percent of the total. The Violin Spider and the “Brown Recluse” can have a serious bite which can cause some tissue necrosis and a wound that takes a very long time to heal, allowing a secondary infection to set in.
Spiders and other arachnids are regular inhabitants of our gardens. Spiders are well known for capturing and consuming all types of insects, including many pests. Besides being important pest controllers, they are fascinating to watch. Walk into your garden at daybreak and look at the orbweaver¹s web glistening like diamonds with the clinging morning dew. During your afternoon weeding session, marvel at the alert jumping spider who is watching you as attentively as you are watching him. While picking your bouquets, observe how well the Crab Spider camouflages itself on your daisies, or how the Green Lynx Spider seems to become one with the leaves. Imagine what your garden would be like without these useful friends.
Scorpions, likewise, are predators, feeding on many types of small invertebrates. They are periodically found in some localities under rocks, bricks, leaf litter and fallen branches. Even though they can have a painful sting, our local scorpions (here in California) are not dangerous. However, there are some Centroides species that can have a dangerous sting.
Mites are arachnids that can be either beneficial or a pest, depending on the species. In the gardens, some of the troublesome mites are the Spider Mites, Citrus Red Mite, Six-spotted Mite, Two-spotted Mite and Clover Mite. Many of these can be quite injurious to our economically important plants, especially citrus and avocado. Many mites, though, are beneficial. Soil Mites are abundant wherever leaf litter and deep soils occur. They are important in promoting soil fertility through their digestion of organic matter. Predatory mites, Phytoseiulus persimilus, feed on other pest mites such as Red Spider and Two Spotted Mites.
Millipedes are harmless, many-segmented, many-legged scavengers. They are characterized as having a long, usually cylindrical, multi-segmented body, two pairs of short legs per apparent segment and a short pair of antennae on the head. When disturbed, millipedes often roll into tight coils. Many can secrete noxious fluids from specialized glands along their body to repel predators. They are found in cool, moist areas (in rotting logs, under rocks and leaf litter etc.) where they feed mainly on decaying vegetative material and fungi. Millipedes cause little or no damage to our plants.
Centipedes are multi-segmented predators with the following characteristics: They have one pair of long, running legs on each segment. The first pair of legs behind the head are modified into “poison claws” used for capturing prey. He has one long pair of antennae on the head Although venomous, the toxin is rarely dangerous to humans. Most, however, have “fangs” that are too small to be able to pierce human skin. These interesting invertebrates inhabit the same kinds of habitat as the millipedes; cool, sheltered, moist areas under stones, rotting leaves, fallen branches, etc. They are easily distinguished from the millipedes by their longer cursorial (running) legs and the fact that they will run very quickly if disturbed; whereas, the millipede will coil into a tight spiral. Centipedes are beneficial hunters.
Most crustaceans live in fresh or salt water. They include the lobsters, crabs, shrimp, barnacles, crayfish and various tiny, sometimes microscopic aquatic and marine organisms such as copepods, Daphnia, and Triops. Crustaceans generally have 10, 12 or 14 legs and 2 pair of antennae. The most familiar terrestrial crustaceans are the Sow Bugs and Pill Bugs, sometimes called “roly-polies”. The Sow Bug is considerably larger than the Pill Bug and has two prominent tail-like appendages. It is incapable of rolling itself into a ball. Most of us were introduced to these critters as children. To this day, children around the world are charmed and delighted by the Pill Bug’s ability to roll into a tight ball when disturbed. Every gardener is well acquainted with these harmless little fellows. Commonly assumed to be insects, these are crustaceans, more closely related to shrimp and crab than to insects. Having descended from aquatic animals, they retain their gills and require a moist environment to survive. They are frequently found in any cool, damp location around the yard and are sometimes considered a nuisance by some gardeners. Both Pill Bugs and Sow Bugs are omnivorous and feed mainly on young and decaying plant material. Unless very numerous, they do little damage.
Now that we know about these wondrous critters, let’s find them!
Most insects, and the other arthropods as well, will be hiding (sometimes even hiding in plain sight!). You will need:
- jar and lid or other such vessel
- tweezers or forceps
- magnifying glass or jewelers loop
- butterfly net
- lots of patience and good eyes
Some of the best daytime places to find insects are:
- in and near water
- in grassy meadows
- under rocks, fallen logs, leaves and trees
- on the undersides of leaves
- inside flowers
- in shrubs and trees
The determined searcher may even want to build a trap. There are several kinds. The following is from The Regents of the University of California’s “How to Set Insect Traps.”
One step in the collection of insects in an area is to set insect traps. These will generally attract crawling insects such as ants, beetles, and the like. These traps will give you a fairly good guesstimate as to the numbers and varieties of ground insects in your area.
Large plastic cups (2 per trap)
Propylene Glycol (such as “Sierra” brand anti-freeze/coolant)
*Note – it is important to use propylene glycol as opposed to the more common Ethylene glycol. The Propylene is eco-friendly and also non-toxic, so if it spills, it will not hurt students, and animals can taste it without getting ill (NOT STUDENTS!).
Fine sieves for collecting
Each area or level of the site should have a separate collection. For example, when collecting in a Canyon, collect on the bottom, in the grasslands, at the middle level and the rocky ledges, and on the mesa top. 5 – 10 traps should be set in each area and the traps must be at least 10 meters apart.
For each trap, dig a hole large enough to set in two plastic cups (one inside the other) so that the lip comes to ground level. Pack the dirt around the cups so that the insects who are walking along the ground in that area will just fall into the cup. After the cups are set, empty the top cup of any dirt or debris, and then fill about 1/4 way up with the glycol. Set the top cup back inside the bottom cup. Use the flagging material to flag the site by tying some on a tree branch above the trap.
Traps can be set for any amount of time, but the longer the better. If a long term trap is set, then some sort of canopy or cover should be set up to prevent the traps from filling with rain water, etc. Tim uses plastic plant saucers with nails stuck through them that he can just pound into the ground around the traps.
COLLECTING: When collecting, students need a sieve to pour the liquid through, then the insects are dumped into a common collecting jar for later identification. If you are going to reuse the traps, you may also reuse the glycol after the insects are strained out. If you are through with the traps, be sure to collect all the cups as well as the identifying flags as these items are NOT environmentally friendly.
Copyright © 1998-2001 The Regents of the University of California http://www.lanl.gov/misc/copyright.html
Even though this one calls for propylene glycol (non-toxic anti freeze) which will kill your insects, or other animals that may enter it, you may substitute this for another bait. Try a sugar/water mixture, ripe bananas etc. which will attract, but not kill your insects.
In the evening, insects (especially moths and some beetles) can be found swarming around lights. You can also set up a “black light”: Drape a white sheet across a shrub, fence, or other vertical object outside in a dark place. Place a battery operated lantern on the ground a few feet in front of the sheet (bulb/flourescent tube may be replaced with a black light which attracts insects better). Watch the insects swarm around and dive bomb the sheet. Great fun!
Now that you’ve found some “bugs”, follow the curriculum project link and create a new home for your new acquaintances.
In future articles, I hope to include other equally unloved and uncherished creatures, but, for now, I hopefully have succeeded in answering many of your unasked questions and dispelled many myths and rumors of these, our most misunderstood friends.