CHAPTER 14

 

 

Beetles

This is by far the largest order of insects; it contains over 40% of all known insect species. Most entomologists think there are over 3 million undescribed species of beetles. Assuming this to be true and excluding other arthropods, there are over three times as many beetle species as all other species of plants and animals combined. Beetles vary in length from nearly microscopic to over 8 inches. One of the most distinctive features of the beetles is the front pair of wings (elytra) that are hardened or leathery and which meet in a straight line down the back of the abdomen (Figure 14A). These structures are strictly protective and not used in flight. When a beetle begins to fly, the elytra are parted, exposing the second pair of unfolding flight wings.

 

                                                          Figure 14A. A guitar beetle-approximately 3 inches in length. Right image showing elytra of beetle in flight courtesy  

                                                                                                                                                         Peter Chew.

Beetles possess chewing-type mouthparts. The mandibles are very large, heavily sclerotized, and used for gnawing and crushing. Very large beetles are capable of delivering a nasty bite. I once acquired several rather large stag beetles (Figure 14B) from Indonesia. At the time of purchase the dealer indicated we should be very careful. He explained that when a stag beetle bites, it is very painful and difficult to pry one’s body part from the beetle’s mandibles. He further indicated that one way to remove a clamped stag beetle was to apply heat (a match) to the abdomen). Within a week of my return home one of these beasts had clamped onto my finger and the match trick worked well. Because I had already sent 2 of the beetles to one of the prominent U.S. insect zoos, I decided I should warn them of this potential hazard. During my call, the director indicated that one of the technicians currently had her hand in the freezer in the attempt to freeze a stag beetle off her thumb-too late!

 

 

Figure 114B. Male Indonesian stag beetles with greatly enlarged mandibles.
The males use these structures to fight over females.

Ladybugs, Ladybird Beetles. The ladybugs are a well-known group of oval, brightly colored beetles with clubbed antennae (Figure 14C). Almost all are predaceous in both the adult and larval forms and the majority is host specific. Consequently, ladybugs are considered to be one of the more useful predators in biological control. Many ladybug species feed on aphids, but others attack mites, mealybugs, scale insects and whiteflies. One ladybug can eat 5000 aphids in its lifetime. This is why at times they have been called "aphid lions."

 

Figure 14C. An adult ladybird beetle.

 

The convergent ladybird beetle is one of the most notorious species (Figure 14D). Adults of this species commonly are sold by nurseries, department stores, and home and garden centers. Homeowners buy and release them in their yards for aphid control. Although this species can control aphids quite effectively in nature, the well-intentioned practice of mass-releasing the convergent ladybird beetle for aphid control is considered worthless generally.

 

Figure 14D. The larval stage of a convergent ladybird beetle.

The reasoning behind this statement is associated with the seasonal cycle of this beetle. In the valleys of Southern California and other areas, adult and larval beetles commonly feed on aphids in the spring. As the season progresses and the aphid population begins to disappear, the behavior of these beetles change drastically. In late fall the adult beetles fly to an elevation of about 5000 feet and follow the winds to the mountain passes. Soon after arrival the adult beetles enter into a condition called reproductive diapause. While in this stage, the beetles congregate into huge clusters (sometimes many thousands per cluster) and hang on rocks and trees (Figure 14E). In diapause, the physiology of the beetle slows down. They do not feed or reproduce, but are capable of movement when prevailing temperatures are above 50 degrees F. This condition allows the beetles to survive the winter without food and in freezing conditions. In early spring they emerge from diapause and fly back to the valleys to lay eggs and resume their feeding on aphids.

 

 

Figure 14E. Overwintering convergent ladybug adults. Image courtesy  James Solomon, USDA Forest Service, Bugwood.Org.

The main environmental factor that triggers these beetles into and out of diapause is day length. On a yearly cycle this is the only consistent factor in their environment. On a given date at any time of the year the amount of daylight and darkness is always consistent. Environmental conditions such as temperature on any given day of the year are inconsistent and, therefore, would be very unreliable as a diapause triggering factor. If this environmental condition were used, it could be disastrous to the beetles. A few hot days in December could trigger the beetles out of diapause, resulting in their flying back to the valleys where few, if any, aphids would be present.

Unfortunately, the beetles that are sold commercially are collected from the mountain passes and sold in the spring while they are still in diapause. So of course they do not feed or reproduce. Even f they are released in a yard and then emerge from diapause, they follow their natural instinct and fly away.  Typically when purchased directions include releasing the beetles at night in order for them to settle down. Of course the real reason is probably that they do not want the homeowner to see the beetles fly away.

A homeowner might be fooled into thinking he or she has a hard working bunch of ladybugs after such a release because a few individuals still remain in the yard. However, these probably are members of the small percentage which have been parasitized by wasps. These unfortunate beetles never develop normally—they can't fly or feed well and they do not reproduce.

The winter-collected beetles can be artificially triggered out of diapause by exposing them to the photoperiod (amount of daylight vs. darkness) normally present during the springtime. Even when this is done, apparently the beetles still require an extended flight period prior to settling down to feed and reproduce.

A considerable amount of research has been conducted in the attempt to prevent the need for this flight period. Scientists have turned the beetles in large tumblers over long time periods, attempting to simulate flight. They have even tried gluing the elytra together to prevent this flight. Nothing has been successful.

The use of another ladybug, the vedalia beetle (Rodolia cardinalis), is one of the first examples in the United States of how humans can use predators successfully to control a pest species (Figure 14F). The cottony cushion scale was accidentally introduced into California on acacia imported from Australia. Once introduced into California, it became a major pest on citrus. Soon after its introduction, this scale threatened the existence of the emerging industry in California. During this period (1888-1889), there were no effective pesticides available for the control of this pest.

 

 

Figure 14F. A vedalia beetle consuming a nymphal cottony cushion scale.
Image compliments Charles Hogue, L. A. County Natural History Museum.

Entomologists from the USDA, realizing that this scale was not a pest in Australia, suspected that its non-pest status there probably was due to the presence of effective biological control agents (insects eating and controlling other insects). Based on this premise a team of scientists was sent to Australia to search for predators and parasites of the cottony cushion scale. Several were found and brought back to the United States to be colonized and released. The most effective of these was the vedalia beetle, a ladybug. Upon introduction, this beetle soon became established throughout California and reduced the scale to a non-pest level within a two year period. Since that time the cottony cushion scale rarely, if ever, becomes a pest due to the ever-present activity of this ladybug. This introduction was the first of many successful programs where biological control agents have been introduced into the United States and other countries following the accidental introduction of pests.

                    Scarab Beetles.  This is a very large group of beetles that differs greatly in size, color and shape. The scarabs are heavy-bodied, oval shaped with lamellate or feather-like, antennae (Figure 14G).

 

 

Figure 14G. Two of the more beautiful scarab beetles.

The rhinoceros beetles are a common group of scarabs and among the largest known Coleoptera (some South American species reaching 8 inches long). These beetles are so named because the males bear horn-like projections on their heads. One or more horns may also be present on the thorax. When 2 males of the same species come together in the presence of a female, they frequently will fight or joust with their horns. This is part of the mating ritual.

In Thailand and other countries rhinoceros beetles are frequently collected for the purpose of fighting. Two males are placed at each end of a 10-inch section of bamboo with a female in the hollow section of the plant (Figure 14H). Although smaller amounts are more common, Thai people sometimes bet large amounts of money (several hundred dollars) on the outcome of the males' battle. Generally the largest beetle wins by knocking its opponent off the bamboo. Fighting beetles are sold on many street corners; larger specimens can cost upwards of one hundred dollars.

When we were in Northern Thailand, we bought the losers for 40 cents. (We couldn’t afford the winners!) On another recent trip, we visited Malaysia prior to going to Thailand. In Malaysia, the fighting beetles are the same species but about twice the size of their Thai relatives. I brought one of these giants to Thailand with the idea of winning a fight. When this beetle was placed on a piece of bamboo with its smaller relative, it didn’t bother trying to throw the other beetle off. It lowered its center horn and trapped the other beetle between its two opposing horns, drove the center horn through its opponent and finally shook its head violently, throwing pieces of the other beetle in all directions.

 

 

Figure 14H. Two male 5-horned rhinoceros fighting over a female. Typically the larger beetle will win.

The green fruit beetle is one of the best-known scarab beetles in the United States. The adults are large (about one inch long) and green, with the lateral margins fringed with yellow or bronze (Figure 14I).

 

 

Figure 14I. An adult green fruit beetle feeding on a fig.

These large day flying beetles are commonly seen in summer months. Green fruit beetles feed on ripened fruit such as grapes, peaches, figs, plums and nectarines. Although their feeding habits can cause great stress to the homeowners, they are of little concern in agriculture. They are attracted only to ripe fruit. Fruit raised for agricultural purposes normally is picked green and allowed to ripen. The larval stage of this beetle, as is that of all scarabs, is a C-shaped, dirty white grub with well-developed thoracic legs and head capsule (Figure 14J). These larvae typically are found in the soil and feed on the roots of ornamental plants and decaying vegetation. The larvae of the green fruit beetle commonly are found in compost piles, accumulated horse manure, rabbit droppings, and chicken feces.

 

Figure 14J. A typical larval stage of a scarab. Frequently found in the soil
feeding on roots and other plant material.

The Japanese beetle is, without a doubt, the most damaging scarab beetle in the United States. The adults are about 3/8-inch long, and broadly oval with brownish elytra. The head and thorax are greenish bronze (Figure 14K).

 

 

Figure 14K. An adult Japanese beetle. One of the major pests in the eastern U.S.

This beetle was imported accidentally into New Jersey in 1861. Subsequently it has spread to most states east of the Mississippi River. Both the adults and larvae are extremely damaging to a wide variety of plants. The larvae feed on roots of grasses (turf) and other plants, while the adults skeletonize leaves and feed on fruit.

The Japanese beetle is such a major pest in the eastern United States, that several western states have rather extensive programs to prevent the accidental introduction of this pest. Commercial air flights (both cargo and passenger) that come to California and other western states from the east are checked during the summer months for adult beetles. Traps baited with pheromone-like chemicals that are attractive to adults are placed around the state in the hope that should this beetle become established in an isolated location, its presence would quickly be discovered. Control procedures could then be installed to eradicate the pest before it became established over a wide area.

Dung scarabs exhibit a unique behavior. A male and female beetle will select a likely dung pile (usually fresh), cut out a ball of the dung and roll it away with one beetle pulling while the other pushes (Figure 14L). The ball subsequently is buried in the ground and an egg is deposited in it. Subsequently the hatching larvae feed on the buried feces.

 

Figure 14L. A male and female elephant dung scarabs rolling a dung ball.

This behavior is considered beneficial because dung scarabs, in most areas of the world, are the first insects to attack the feces of wild and domestic animals. Apparently, without this initial burrowing, dung is not readily eaten or decomposed by fungi, bacteria or other animals.

Australia is a country where the importance of this beetle was recently demonstrated; cattle have become one of the three major industries there. As most people know (possibly not!), when a cow defecates the result is a rather large, moist pile of feces (known as a cow pie to some). The only naturally occurring mammals (other than humans) in Australia are marsupials; marsupial dung is rather dry and pellet-like; consequently, there were no native dung scarabs attracted to the cow pies. Much of the range land became covered by dried cow feces over time and large tough weeds of no grazing value developed around the perimeter of each pile.

The Australian government, being quite biologically control oriented, decided to import several species of dung scarabs for dung control (Figure 14M). This initial importation was quite successful as these imported dung scarabs readily destroyed newly formed cow pies. However, a separate problem developed when a moth became a pest on wheat. Australian officials decided to import toads to control the wheat pest. Unfortunately, the toads were attracted to the dung scarabs as well as to the moths. When a cow defecated, the toads would scurry over to sit next to the cow pies and wait for the dung scarabs’ arrival. Soon most of the imported scarabs were consumed.

Figure 14M.  Two of several dung scarab species.

Next, the officials decided to import a larger species of dung scarab with the idea that the toads wouldn't eat such large insects. Where do you go to find large dung scarabs-Africa (Figure 14L)?  When an elephant defecates!-anyway a large species of African elephant dung scarab was introduced. Unfortunately, the toads attempted to eat these scarabs also; but large beetles are quite strong and, after being swallowed, the scarabs simply ripped open the toads' stomachs and crawled out—thus killing most of them. The latter situation was not a totally bad development. The imported toad was the cane toad. This toad has become a major problem in several countries as it has extremely toxic poisons in its skin, which it readily exudes when disturbed. As a result there have been many cases of poisoning of domestic animals and humans.

Figure 14L.  A 3  inch giant African dung scarab.

Beetles, and more specifically scarabs, have been important in many ancient cultures, looming high as religious symbols. So called "pendants" in the shape of beetles are known from the late Paleolithic epoch (10,000 to 20,000 years ago). It is thought that beetles played this role partially because of their ability to fly and their importance as food. Shamans (medicine men) historically played extremely important roles in these societies and had great power. They were thought to be able to fly in the sky (in dreams and trances) and descend to subterranean hells to act as mediators between mortals and the "infernal powers." With such power being held in high esteem, it is quite apparent how a beetle such as a dung scarab could become an important religious symbol, as they also could fly and dig into the earth.

In current day shamanistic societies, the scarab still plays an important role. In some South American Indian tribes, a big dung scarab named Aksak was thought to have modeled man and woman out of clay. In a more remarkable Indian myth, an aquatic beetle plunges to the bottom of the original liquid chaos to scoop up subterranean matter to form the terrestrial earth. This original beetle was thought to be a cross between an aquatic diving beetle and dung scarab.

The dung scarab played its most famous role in ancient Egyptian culture. It was thought that a giant dung scarab was responsible for rolling the sun across the sky each day. This conclusion was based on the Egyptian priest-scholars' observation of the daily activity of the dung scarab, Kheper aegyptiorium (Figure 14M). They thought the scarab ball was something like the beetle’s eggs. They further observed that the scarab buried the dung-egg ball in the soil, which turned into worm-like creatures (larvae), eventually turning into a dead corpse-like form (pupae)—only to be reborn again as a beetle. They further concluded that what happened to the sun was not that much different than the scarab’s metamorphosis. After the giant scarab buried the sun at the end of the day (setting of the sun), the sun traveled underground from west to east, going through a metamorphosis which resulted in rebirth from a corpse like stage as the sun rose.

 

Figure 14M. Kheper aeqyptorium, the sacred scarab of ancient Egypt.

The priest further concluded that if the lowly dung scarab and the glorious sun could go through a metamorphosis and eventually be reborn from a corpse-like stage, why could this not be possible for humans? The recipe for rebirth then was to imitate, as closely as possible, what happens to the scarab once it enters the ground. Most crucial was the last stage (the pupa) which inspired the invention of the process of mummification. In all probability the mummy is nothing more than an imitation of a scarab pupa.

As mentioned earlier, Kheper aegyptiorium is the sacred scarab. Khepera is what Egyptians called scarabs. They were so honored as gods representing regeneration, virility and new life, that many of the kings (pharaohs) took Khepera as part of their own names. King Tut (Tutankhamun), for example, used the name of Neb Kheperu Ra. This was his "official" name. Sometimes a certain king's name would be inscribed on the back of many scarab amulets (in his honor). Some of these would be worn for hundreds of years after the king's death.

                                                                                          Giant Rhinoceros Beetles (Scarabs) of the World

These are some of the most sought after beetles by those who have insect collections and also contain some of the largest insect in the world.

Atlas beetle, Chalcosoma atlas.  This is a species of beetle found in southern Asia, especially Malaysia, remarkable for its size (2 to 6 inches). As common in many insect species, the male is larger than the female and usually two males will fight for a female for mating. The Atlas beetle is, like other beetles of the genus Chalcosoma, notable for its size and the horns. The Atlas beetle differs from other Chalcosoma species (such as C. caucasus) in the end of the cephalic horn of the Atlas, which is broadened.

The larva of the Atlas beetle is known for its fierce behavior, including biting if touched. Unverified reports exist of larvae that live together fighting to the death if there's not enough space or food. In addition the adults can give a nasty bite.  They also have a sharp ridge between the top of the thorax and base of the elytra.  I once caught a rather large specimen and made the mistake of handling it carelessly.  Needless to say it took a hunk out of my finger and in a hurry I grabbed it unfortunately in the ridge area.  It arched it thorax and took another chunk of of my hand.  Of course needless to say in trying to remove it from my now bloody hand it grabbed me with its sharp tarsal claws and strong legs (these guys are very strong) and proceeded to rake my arm as I pulled it off.

                                          

                                                                                                   Larva and Adult of Atlas Beetle.

The origin of the name of the Atlas beetle may be the Greek Titan Atlas or the Atlas Mountains. The fact that the Caucasus mountain range gives its name to another beetle of the same genus (C. caucasus) m

Elephant Beetles, Megasoma elephas.  They are classified with the Neotropical rhinoceros beetles. Elephant beetles are black in color and covered with a coat of fine microscopic hairs. The hairs grow particularly thick on the beetle's elytra. The hairs give the beetle's body a yellowish color. Males have two horns protruding from the head and another from the prothorax. Females have no horns. The horns are used for defense in competition among males for food and mates. In size, Elephant Beetles range between 70-120 mm; males are sometimes even bigger. Males are around 2 to 3 times bigger than the females. Elephant Beetles are located in southern Texas, southern Mexico, Central America, in South American rainforests, and in parts of Australia.

 

Elephant Beetle.  Image Courtesy of Derek Ramsey (Ram-Man)

 

Hercules Beetle (Dynastes hercules).  This is the most famous and largest of the rhinoceros beetles. It is native to the rainforests of Central America, South America, and the Lesser Antilles (Clemson University). Their title is well deserved, with some (exceptionally rare) males reaching 6.75 inches (170 mm) in length. It is the largest of the 6 species in the Dynastes genus, and one of the largest beetles known, being exceeded in length by only two other beetles in the family Cerambycidae, Macrodontia cervicornis (specimens of 170-175 mm are known) and Titanus giganteus

 (also up to 170-175mm; several seven inch specimens are reputed/alleged to exist). However, if the horns are excluded, this species drops considerably farther down in the size rankings. One reason for this is that the development of the horns is allometric