Whether as water striders, bloodsuckers, or colorful garden dwellers, bugs are known for their wide variety of forms, lifestyles, and habitats. They exist as plant suckers, as predators, and also as parasites. They live in a wide variety of biotopes, including meadows, forests, and human homes.
But these arthropods, often considered useless, are characterized by much more potential: Their diversity has produced phenomena such as foul-smelling secretions to protect themselves from enemies, shrill sounds as a mating call, special breathing to survive in water, and, in addition, they all possess extraordinary immune defenses. Some species also exhibit perfect camouflage costumes or enter into symbiotic relationships to even eat poisonous plants.
All bugs are considered insects.
But how did these numerous species of bugs with their special adaptations evolve? Which species can be found in the home garden? And isn’t it a fallacy that humans often think of bugs only as pests? Couldn’t we even take advantage of the potential of these insects?
Common features of a typical bug
There is no chance of displacing them. Thanks to their survival skills, enormous food spectrum, low land requirements, and defense mechanisms, bugs have an enormous biodiversity and are widespread worldwide. And although bug species differ greatly from one another, they all have a few things in common.
Insects belonging to other orders, such as ants, bees, beetles, and butterflies, are not considered “bugs.” The term “bug” is only used for the order Hemiptera or Heteroptera.
Of the approximately 40,000 known species of bugs worldwide, about 3,800 live in the United States, and 3,000 live in Europe. Like the related cicadas (Auchenorrhyncha) and plant lice (Sternorrhyncha), bugs belong to the order Hemiptera. The name describes their commonality: Beak-like, piercing-sucking mouthparts. Biologists divide bugs into 23 subfamilies and seven suborders. The species can also be divided into water bugs (Hydrocorisae), water striders (Amphibiocorisae), and land bugs (Geocorisae) according to their way of life.
They survive everywhere
Bugs are found in almost all habitats. It is true that most species of bugs like warmth and dryness. However, some species prefer wetter habitats, and others live in bogs, sandy habitats, or salty habitats. There are also aquatic species that live in water, as well as species that exist on the water’s surface. Sea skaters from the genus Halobates are the only insects that even live permanently in the open ocean.
The worldwide distribution of bugs is favored by their diverse feeding habits: Bugs primarily consume plant juices. However, there are also a number of assassin bug species that feed on other insects and fungi. A few species are ectoparasites that suck blood from larger animals, such as the bed bug (Cimex lectularius). Regardless of the type of feeding, however, all species of bugs can only eat liquid food. They have special tools for this purpose.
The mouthparts on the bug’s head are typically equipped with stinging bristles, which have sharp little teeth at their tips. With their help, the insects bore tiny holes in plants or prey. The food is then ingested via a proboscis, which is located directly on the underside of the head. It consists of two thin tubes with which the herbivorous bugs suck in the nutrient-rich juices.
In the case of carnivorous bugs that eat meaty foods, the intake of nutrients is somewhat more complex: the bugs pump digestive juice into their food through one tube, which, for example, decomposes the dead insect. Through the other tube, they suck up the predigested food pulp.
The feet of the bugs have claws, adhesive lobes, or hairs and can thus be used for running, jumping, or swimming, depending on the species. On the ventral side, the thorax has special scent glands. With this, many bugs spread a foul stench in case of danger, which deters attackers. At the same time, the bugs communicate via their scents. Larvae, for example, emit a community pheromone that leads to the formation of large groups.
The carapace varies greatly in color and shape among the different bug families; this usually allows the species to be distinguished. Their forewings are thickened and leathery at the base, and membranous at the back. The bugs owe their Latin name Hemiptera—half-wing—to this dichotomy. The hind wings are always membranous. However, there are also short-winged or wingless species of bugs.
Mating at will
Speaking of diversity: When it comes to mating, bed bugs have developed very different, sometimes bizarre methods. The most unusual is that of the bed bugs (Cimex lectularius), whereby the male attacks the female without advertising behavior and immediately mates. Sickle bugs, on the other hand, sit on the female for hours, clutching it with their legs. Many families of bugs, such as the tree bugs (Pentatomidae), red bugs (Pyrrhocoridae), marginal bugs (Coreidae), and stilt bugs (Berytidae), mate abdomen to the abdomen. Netbugs (Tingidae), on the other hand, sit perpendicular to each other. In bark bugs (Aradidae), the male sits below the female during mating.
To lay their eggs, females of several species of bugs have an ovipositor. This is used to drill the eggs into the soil or plant parts. Other species, on the other hand, have only a strongly deformed ovipositor. These females bury the eggs or stick them to plant parts, usually in groups of 20 to 30 eggs. The females of the Mediterranean marginal bug Phyllomorpha laciniata handle egg laying in their own way: They often glue their eggs to the wings of the males.
Some females pack their eggs in special pads that also contain bacteria. The newly hatched nymphs suck these up as food – an example of this is the ball bug Coptosoma scutellatum. Several species of bugs practice brood care: The eggs are guarded by the mother until the hatching of the young and also for some time afterward and are temporarily covered with the body. In case of danger, even the nymphs can turn their abdominal backs with the scent glands towards their attackers.
Unlike butterflies or beetles, bugs do not pupate. Instead, they usually go through five stages separated by molts as they develop from embryo to adult. In the course of these, the nymphs gradually become more and more like adults. After their last molt, they are sexually mature and can mate again.
The most bizarre bugs
Bugs are among the most diverse insects of all: whether tree bugs, red bugs, striped bugs, or jumping bugs, they usually live up to their names. Despite their similar anatomy, however, quite different adaptations evolved.
The green stink bug or shield bug (Palomena prasina) is also one of the land bugs common in some countries. It owes its name “stink bug” to its foul odor, because, in case of danger, the stink glands on its abdomen secrete a foul-smelling and long-adhering secretion. In addition, the bugs are green in color in the spring and even undergo a color change: Before overwintering, they turn brown to bronze. Sometimes they also bear a dark transverse band on the neck shield.
The insects, which are up to 14 millimeters in size, prefer to live on deciduous trees such as basswood/linden and alder, but also on thistles and nettles. Despite their nickname, however, they hardly cause any damage.
Some species of bugs come up with very special adaptations and strategies. Some of them are to the detriment of humans: On the one hand, pests in agriculture are responsible for large crop losses. On the other hand, common bloodsuckers can transmit diseases.
Pest with bacterial helpers
A special pest in agriculture is the red cotton stainer bug (Dysdercus cingulatus), which belongs to the red bugs. It eats toxic cotton seeds and leaves permanent discolorations on the cotton fibers, which is why the pest is also called the cotton dyer. But how can this bug utilize the toxic secondary plant compounds of cotton as a food source?
The animal has invisible helpers. The cotton stainer bug carries bacteria in its gut that apparently help it utilize inedible food. Overall, cotton stainer bugs harbor a highly specific community of three to six bacterial symbionts in a specific region of the midgut.
The symbionts are transferred from the mother bug to the eggs. The newly hatched nymphs suck on the surface of the eggshell and ingest the bacteria there. This ensures that the bugs retain the symbionts throughout their lives and later pass them on to the next generation.
When the bugs were deprived of this bacterial helper in experiments, they showed clear signs of malnutrition. The symbionts make an important contribution to the food utilization of their hosts. However, it is still unclear whether the symbiotic bacteria detoxify the cotton seeds, or whether they just break down additional nutrients.
Camouflage and deception, lying and cheating—it’s the same in the animal and plant worlds. Some animals imitate their environment and are thus cleverly camouflaged from enemies. For example, the “walking leaf” is an insect (Phylliidae) that imitates a leaf unnoticed. Mimicry goes one step further, in which the animal sends out an imitated, i.e., fake, signal in order to deceive a third party.
And it is precisely this strategy that the bug Hyalymenus pursues as a representative of the broad-headed bugs. This bug species is highly visible, yet hardly recognizable. This is because it resembles ants in appearance and behaves in the same way. Predators that have learned to avoid ants because they are aggressive and spray acid also avoid their imitators, a promising attempt at deception.
The whimsical adaptations of bug species go back far into the past. Scientists discovered a petrified, fossil Tingidae in 2015. It was the first bug find of its kind in the North American oil shale deposit. There are a total of 53 species of fossil bugs worldwide.
The unusual thing about this fossil bug is its amazingly large antennae. At 4.6 millimeters long, they are as long as the entire body of the Tingidae and have an unusually thickened end. The antennae were interpreted as a tool used by male bugs to land with female bugs. Such optical features to increase attractiveness are widely known in the animal world, similar to peacocks. But the expert also considers the use of antennae to drive away male competitors possible. What is certain is that this feature was first described for the family Tingidae.
The team of scientists found a total of four bug fossils belonging to previously unknown species in the collections of the National Museum of Natural History in Washington. However, the classification of the finds has not yet been conclusively determined. The fossil bug is described as Gyaclavator kohlsi and is estimated to date from the Eocene, about 50 million years ago.
Hard to miss: the red bugs
Particularly large aggregations of larvae and adults can be found in the red bugs or “firebug”. (Pyrrhocoridae). They are named after their strikingly bright red-black coloration. They also have long antennae and short wings. For hibernation, the bugs hide in ground litter or in wall cracks and dare to go outside in sunny weather as early as February or March. The red bugs have a preference for mallows, but also for basswood/linden trees. They are often seen in large flocks of hundreds on tree trunks. However, they do not cause damage even in this quantity.
The red bugs with 300 species feed mainly on plants, but also on the juices of dead and living animals such as mites and aphids. Even their own conspecifics are sucked in by them on occasion. For humans, however, they are harmless despite their conspicuous warning costume: the red bugs are not human parasites and do not transmit diseases. However, they should not be touched because of the bad-smelling secretions they secrete in defense.
Care should also be taken with the dock bug (Coreus marginatus), which prefers to leave its digestive juices in blackberry bushes. If you mistakenly taste a blackberry that has been eaten by dock bugs, it will taste slightly bitter. Dock bugs are pure herbivores. In spring, larvae and adults suck mainly on sorrel leaves, and in summer they like to go after ripe blackberries. As with many species of bugs, adults and larvae of the brown dock bug often congregate in large numbers.
On the trail of bed bugs
In the world of bugs, herbivores as well as carnivorous representatives evolved. The bed bug (Cimex lectularius), on the other hand, has developed a completely different food source for itself: it feeds on human blood. But this was not always the case: originally, the blood-sucking insects fed on bats. So how did the change in the diet come about?
Bed bugs are considered a nuisance pest: During the day, they are invisible and lurk in mattresses of hotel rooms and apartments. But as soon as darkness falls, they dare to come out of hiding and become all the more active. Once they have found prey, the bugs attract each other by means of odorous substances and form larger clusters.
Then the nocturnal sucking begins: a bed bug needs up to ten minutes to ingest its bloody food, the amount of which can reach seven times its initial weight. The adult insects are initially paper-thin and reach a body size of up to nine millimeters when fully sucked.
The bugs are hairy and reddish brown in color. Their receding forewings, lack of hind wings, and flat physique allow them to enter narrow spaces particularly well, where they retreat into the dark after their blood meal. The next morning, only the traces of the stubborn bloodsuckers become noticeable: Violently itchy, red welts on the skin bear witness to the nightly blood meal.
The bad news is that the six-legged bloodsuckers are increasingly spreading around the world, especially from travels to southern countries. In large cities, some bed bugs are already developing resistance to insecticides.
Pests of the past
And bloodsucking has not only existed since modern times: the oldest fossil findings of the Cimicidae—the family of bed bugs—to date came from Egypt. There, the 3,500-year-old remains of such bloodsuckers were discovered in 1999. In the Paisley Caves in Oregon, archaeologists led by Dennis Jenkins and Martin Adams of the University of Oregon came across the even older remains of no less than three different species of bed bugs.
The researchers estimated the age of their finds at 5,500 to 11,000 years. This makes them by far the oldest known relatives of the common bed bug, Cimex lectularius. But unlike the bed bug that preys on humans today, the three fossil bed bug species, Cimex pilosellus, Cimex latipennis, and Cimex antennatus, had a different prey in mind: they apparently sucked the blood of bats exclusively.
But why do some species of bed bugs suck human blood today? At that time, people in Europe, Asia, and Africa still lived primarily in caves and often shared this habitat with bats, the first prey of the tiny predators. During this close coexistence, bed bugs eventually transitioned to humans as hosts and continue to do so today. The species in Paisley Caves have not yet made this leap from bats to humans.
Bugs that live in water
Some species of bugs have also conquered oceans and other bodies of water. The water bugs, such as backswimmers and water boatmen bugs cavort in ponds and lakes. Five representatives of this family even drift their entire lives on the high seas.
This way of life requires special equipment for the insects: All species of water bugs have a streamlined body shape and clearly developed swimming legs for locomotion. In addition, the rudder organs are usually covered with bristle hairs to increase their surface area. Less buoyant species prefer to crawl and climb around on aquatic plants or stones.
Another characteristic feature of water bugs is their often well-developed forewings. However, they usually cannot fly. The antennae of aquatic insects are strongly shortened and are not visible from above. Water bugs are almost universally predatory animals that prey on stagnant water with the help of their proboscis.
Some water bug species have specific breathing tubes on their abdomens that extend out of the water. The bodies of other bug species are instead covered by a film of air held on the back by the wings and on the underside by water-repellent hairs. This air supply is used for respiration. To catch their breath, the bugs appear on the water surface for only brief moments. They leave the water only when they make a change of location or go ashore for hibernation.
Moving on and in the water
Some species are even adapted to live permanently underwater. They take in oxygen via skin respiration directly from parts of the water that are rich in currents. They feed on fish eggs and tiny creatures, which they catch and hold with their short front legs. They use their long middle and hind legs to row and steer. Females lay their eggs on driftwood, bird feathers, or algae.
Easier to find and observe, on the other hand, is the water striders: among them, the sea skaters of the genus Halobates are native to the ocean, with nearly 50 species. They live mainly in warm waters near the coast around the equator. The fascinating thing is that, to this day, it remains unexplained how females find a mate in the vastness of the ocean.
On the other hand, the water strider species of the suborder Amphibiocorisae live on the water’s surface or on the shores of many ponds, pools, and lakes. They include the water striders and marsh treaders (Hydrometridae). The water striders, backswimmers (Notonectidae), and water scorpions (Nepidae) known in the garden pond also belong to the true bugs.
The loudest bug
Very special representatives of the water bugs are water boatmen bugs (Micronecta). These inconspicuously brown-colored insects, which are only two to 14 millimeters in size, can be found in almost all stagnant and slowly flowing bodies of water. However, they are usually only seen when they surface to renew their air supply in the cavity of their neck shield.
The so tiny water boatmen bugs are the loudest animals on Earth relative to their body size. The insect, which lives at the bottom of ponds and pools, makes a noise that reaches 99.2 decibels. The noise produced is thus equivalent to that of a truck passing close by. Although 99 percent of the sound is swallowed as it passes from the water to the air, the chirping is so loud that a person walking along the shore can hear these tiny creatures from the bottom of the body of water, according to James Windmill of the University of Strathclyde.
But what’s behind it? Chirping is only done by the males of the water boatmen, who use it to attract females. The “singing” is produced with the help of a special shrill organ. They do this by bristle fields on the inside of their forelegs brushing against a protruding, sharp edge on the side of their head. The sound-producing rubbing surface on the animal’s leg is only 50 micrometers in size—just as wide as a human hair. The high-pitched sound thus produced is amplified by the air bubble on their front body. However, it is still unclear why the animals achieve a record-breaking volume in the process.
Bugs are survival artists: they are the only insects that live on the high seas and have conquered most habitats. Most of them are harmless to us. Only a small minority are pests. Others, however, have great, undiscovered potential as beneficial insects and helpers.
The ones known as pests
A few species of bugs can cause damage to crops in agriculture when they occur en masse. Among the best known are the Bishop’s Mitre (Aelia acuminata), which enjoys cereals, the sloe bug (Dolycoris baccarum), which feeds on soft fruits, or the rape bug (Eurydema oleraceum), which poses a threat to cabbage crops (a.k.a. the cabbage bug).
In addition to the damage they cause to gardens and agriculture, blood-sucking bugs such as the assassin bug (Reduviidae) also cause problems: These insects, which are especially widespread in Latin America, can transmit dangerous pathogens to humans. Some of the approximately 200 different species could be vectors for infectious diseases, including Chagas disease, which is caused by unicellular parasites. Chagas disease is one of the six major tropical diseases.
As a syringe
Although assassin bugs are disreputable as disease vectors, they may even be beneficial to humans. Scientists use the bugs as “living syringes” because the assassin bug’s stinging proboscis is 30 times finer than the finest medical needle. This means that even the tiny capillaries of small animals such as rabbits, hamsters, or birds can be hit, which is hardly accessible to a conventional syringe. Biologists have already successfully drawn blood from 40 wild animal species, such as meerkats and kangaroos, with the help of the assassin bugs.
But bugs are also interesting for medical research for other reasons. Since bugs do not have an immune system with antibodies – as mammals do – researchers have studied how the bugs protect themselves against bacteria and other pathogens instead. They found that the insects produce effective antimicrobial substances. These defenses could potentially also protect humans from infections and render resistant bacteria harmless. The need is great, because more and more diseases can no longer be cured with common antibiotics.
A sustainability solution
In Mexico, bugs are appreciated for a completely different reason. During the Jumil Day Festival, locals head into the mountains to hunt for pine bugs. The harvested bugs are rolled up in tortillas, lightly salted, and then eaten raw.
Bugs and other insects have some benefits as food: They have protein, fatty acids, fiber, and minerals in them. They also require little space, can live almost anywhere, and reproduce quickly. This means that a large number of them can be grown in a short time in a small space. Insects also require proportionally less feed than other meat sources, such as cattle. For 2.2 pounds (one kilogram) of insect meat, only 4.5 pounds (two kilograms) of plants need to be fed, in contrast to 20 pounds (nine kilograms) of feed for beef.
Insects could therefore become increasingly important for human nutrition in the future, especially in poor regions. And there are plenty to choose from: more than 1,900 insect species are now considered edible, ranging from bugs to butterflies, termites, and grasshoppers to cicadas and cockroaches. Instead of destroying them as pests with insecticides, they could soon end up as a delicacy on the lunch table.