Adaptations And Varying Species Of Insects Biology Essay

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Everyday, human beings interact with different species of insects. They can be found almost anywhere, inside the house, in the garden, even inside cabinets. Nonetheless, human-insect relationship has not made a very good record throughout history. Plagues of locusts in the Bible, giant insect villains in comic books and Hollywood movies, and insectoid enemies in computer games, for centuries most humans dislike insects. As the concept of pest emerged, this dislike became a war. Humans and insects have been fighting over resources provided by nature. "Pests" were condemned and considered as nuisance but behind all these, there is a reason why these organisms emerge as a major competitor of humans. That reason however, is simply an effect of the interaction of humans with these organisms. All these disastrous conditions regarding these organisms are all human-made. In this research paper, reasons how these happened will be stated and explained. As an overview we must first know what "insects" are.

Arthropods under the Class Insecta make up the biggest portion of Kingdom Animalia (Romoser 1994, p.1). Based from their unique characteristics, insects can be distinguished from other arthropods in many ways. Their bodies can be separated into three well-developed portions: the head, the thorax and the abdomen. The head is mainly used for sensing using antennae and for acquiring food while the thorax is for moving and is usually where the wings are attached, the abdomen is used in digesting food, and the one possessing the reproductive structures (Speight et al. 2008, p.2; Romoser 1994, p.1).

Insects can also be grouped according to their sources of nutrition. The detritivores are saprophagous which consume decaying plant and animal materials. The herbivores are phytophagous that eat plants. Some are mycetophagous and eat fungi. Carnivores are zoophagous and eat other animals. Others that can be classified in more than one of the categories are considered as omnivores. (Romoser 1994, p.220)

The insects have been very successful organisms of the animal kingdom. Their sheer numbers are proof of their adaptations and the diversity of their species shows their thriving evolutionary mechanisms. They have been the usual residents of almost any terrestrial environment and they are almost evenly distributed all over the planet (Romoser 1994, p.1).

Insects also play a major ecological role in the food web. Insects are sources of food of many organisms and also consumers that balance the food web (Romoser 1994, p.394). They also have symbiotic relationships with other organisms. It includes parasitism wherein the parasite benefits while the host suffers, commensalism wherein the symbiont has no evident effect on the host, mutualism wherein both organisms benefit from each other and lastly, on an insect's case, parasitoidism wherein an adult female oviposts in a living host and the offspring will eventually kill the host, e.g.,Cotesia plutellae deposit their young on larvae of diamondback moth (Schowalter 2006, pp. 230-231,248, Wajnberg et al. 2008, p.84).

However, because of their ecological triumph the insects have been clashing with the most successful organisms on earth, the humans. From the earliest records, insects have been the natural nemesis of humans. Even though only small portions of insect species are detrimental to humans, members of this group have been agricultural nuisance destroying crops, stored products, fruit trees and other plants causing famine, transporting microorganisms and viruses causing plagues and epidemic and unending terror to human life (Harwood and James, Davidson and Lyon as cited by Romoser, 1994, p.1, 2008, npag.)

Insects could be very protective of themselves and many people consider them as pests because they bite, sting and inflict to defend themselves when provoked (ANTS Documentary, 2007, npag.). This is evident in the Arcadia National Park case wherein swarms of European fire ants infested a nursery school playground stinging any person who gets close to them (Edgecomb 2002, npag.). These natural self-defence mechanisms are often misinterpreted as hostility.

Humans also regard insects as pests because insects damage things valuable to them. Some insects feed on crops propagated by humans. In fact, "crop losses averaged from many published studies reach almost 45% of total yield annually, a colossal loss on food and other products, with potential yield losses to pest (weeds and pathogens as well as insects) ranging from 50% for wheat to a colossal 80% in cotton"(Oerke as cited by Speight et al. 2008, p.29). Technically each developing plant we give importance to is shared with one or more insect species. We can take the apple tree as an example wherein there are roughly 400 insect species infesting it and 25 of which are economically important (Johansen as cited by Romoser 1994, p.397). Majority of the damage rendered by these insects are related with their feeding behaviour. Based on the species' life stage, they chew parts of the plant thus destroying clunks of tissue, drying the plant up by sucking its sap, and/or gashing every portion of the plant. Besides all plant parts, all life stages are in danger of insect attack as well. Razing insects not only damage the whole plant body but may also inject toxins from their saliva that may poison the plant. Resulting from their feeding, a number of insect species are held responsible for the application, transfer and spread of plant diseases principally caused by bacteria, fungi, viruses and some protozoans (Romoser 1994, p.397).

There are other multiple cases of insect interference on the growth of plant crops in the field stated by Romoser (1994, p.397):

"Insects injure small grains in the field from the time the seed is planted until the grain is harvested. Both wireworms and false wireworms feed on the planted seed. In dry soil they may even destroy a crop before rains stimulate germination and growth. After the grain germinates, these pests devour the tender sprouts just as they push out of seeds.

Wireworms also kill seedlings by boring into and shredding the underground portion of the stems. Wireworms and white grubs feed on roots and sever them from the plants. Cutworms, white grubs, and false wireworms cut off young plants near soil level. In addition, the wounds left by soil pests allow rot pathogens to enter the plant.

Grasshoppers, Mormon crickets, and armyworms may devour young plants completely; they may strip the leaves from older plants, feed on maturing heads, or cut through the stems below heads.

By injecting toxic secretions while feeding, larvae of Hessian flies retard or kill seedlings and reduce the yields of older plants. Weakened stems of older plants are likely to cause the crop to lodge. Wheat stem sawfly, wheat jointworm, and wheat strawworm bore within culms and obstruct the flow of sap. This damage reduces the number and weight of kernels. Boring insects also cause grain to lodge.

Insects such as the chinch bug and various aphids impoverish plants by sucking juices from leaves or stems. Moreover, they produce fatal necroses by injecting toxic saliva. Small grain pests may transmit serious plant diseases, such as wheat streak mosaic by the wheat curl mite, striate by the painted leafhopper, barley yellow dwarf by several species of aphids, and aster yellows disease of barley by the aster leafhopper."

Because of these crop infestations, few insect species are regarded as archenemies of farmers as they retard, reduce or totally hinder agricultural production. Though there are some insects that are needed for plants to grow properly but there are others that would be better if they stay away from them (Korrow 2007, npag.)

Furthermore, some insects are deeply despised by humans because they contaminate and damage stored goods, domestic commodities, and building materials.

Stored goods are attacked simply because these products are virtually isolated in containers making them free from natural competitors. "Stored grains are particularly susceptible to attack and probably incur the most damage of any stored material. Stored-grain pests not only consume grain but also render large quantities useless by contaminating it with fecal material, webbing, odors, shed exoskeletons, and whole or fragmented dead individuals (Romoser 1994, p. 398)." Activities of these insects may also increase the temperature of the grain that causes moist air to rise where its temperature is lowered causing it to condense on the grain's surface. Because of this, the grain undergoes caking making it vulnerable to spoilage and emergence of molds (Wilbur and Mills cited by Romoser 1994, p.398).

Food that is packaged may be invaded by insects at any moment from the processing plant until the home of consumers. What is considered food for insects does not necessarily pertain to human food. Insects like the cigarette beetle and drug-store beetle, members of Anibiidae (Coleoptera), devour several nonhuman food materials such as tobacco and several drugs (Romoser 1994, p.398).

Several insect species have been living with humans and even their do little of no harm at all, their existence in the human home is highly unfavoured. A number of domestic items are in danger of insect attack such as household wares, clothes, reading materials and groceries. Any wooden structure may be seriously devastated by insect invasion (Romoser 1994, p.398).

Some insects are vectors that spread parasites and microorganisms that cause diseases. Romoser (1994, p.30) describes vectors as:

"A particular type of insect pest is one that is able to carry diseases from one mammalian host to another or from one plant to another. These hosts may both be human, or one may be another mammal such as another primate or a rodent. They may be wild plants that provide reservoirs of diseases for infection of crops, or they may both be crops. Both local and global epidemics are vectored in this way by insects; the rising importance of malaria, sleeping sickness, plague, encephalitis, and so on illustrate the vital need to explore the intimate ecology of insect-disease associations, in attempts to reduce the colossal and direct impact on human lives. "

Moreover, psychological anxieties caused by insects make human being condemn them. Occasionally insect presence causes disturbances that are possibly totally unrelated whether these insects are harmless of not. Some people have entomophobia. Entomophobia, derived from the Greek words "entomos"(insects) and "phobos"(fear), is the fear of insects or "bugs". Some people that suffer from Entomophobia are also afraid of anthropods and worms which are not scientifically classified as insects. Sufferers of Entomophobia also fear flying insects such as bees and house flies. To sum up the fear, Entomophobia is the fear of any type of "bug", and it can differ among sufferers as to what type of insects they are afraid of (deJongh 2006 p.1)." This is the illogical and constant fear of insect infestation (Romoser 1994, p.400).

Symptoms of entomophobia mainly depend on the degree of a person's fear. Common symptoms are increased anxiety, panic assaults, breath shortness, hyperventilation, increased heart rate, queasiness, perspiration and a feeling of terror. Even though insects do not threaten them, entomophobics literally avoid them in any way possible. "To avoid insects they will seal off windows and doors, constantly clean, and spray insect killer. Whatever repels insects is a solution to the sufferer because it means that there will not be any insects around them to throw them into a tantrum (deJongh 2006, pp. 1-2)."

Many subjects of fear are cockroaches, bees. Some even fear ants like army ants which have extremely longlegs and highly predatory (National Geographic 2009, npag.)

On the other hand, some people hallucinate of insect infestation. This is "a condition in which the subject imagines he is being molested by small and difficult-to-locate forms which reach and localize on the body despite all sorts of extraordinary preventive measures (Romoser 1994, p.400)."

However, in terms of biology, nothing can directly identify an insect as a pest and these pest situations are all human-made (Romoser 1994, p.396).

The term "pest" is created solely on a subjective human basis. It tends to brand organisms based on their ecological activities resulting to a dilemma for humans and their products. "Ecologically, an insect pest is merely a competitor with humans for another limited resource", and this labelling only occurs because these plants or crops were propagated for human use and these herbivores which naturally eat plants are then declared as pests (Speight et al. 2008, p.29).

Pest situations develop because of the modification of the environment. "Human activity has modified the environment, sometimes to advantage, often to disadvantage (Romoser 1994, p.396)." One unfavourable effect created by human activity is the emergence of relatively uncomplicated ecosystems, "generally, the simpler the system of interacting organisms, the less the system's inherent stability and the greater the likelihood of large fluctuations of populations of the component species (Romoser 1994, p.396)." Because of this, it is not easy to comprehend why there is a myriad of problems concerning the great monoculture of organisms particularly in plants that have been developed by humans. Agroecosystem are very much simpler than the previous ecosystems before them thus making it easier for pest situations to surface.

Apart from that, as humans store materials edible to insects such as crop harvests, they create a perfect "habitat" for certain insects and as they keep those materials close to them, they make an ideal way for the dissemination of insect-borne pathogens (Romoser 1994, p.396).

Insects' habitats are being occupied by humans. "Various of the foregoing factors that influence insect species richness can be altered, usually detrimentally, by human activities such as agriculture, forestry, urbanization, and so on. In general, the diversity of insect communities in habitats such as grassland is often negatively correlated with management intensity (Nickel & Hildebrandt as cited by Romoser 1994, p.21). Due to these human activities, insects population increase and are forced to live closer to humans because their natural habitats are crossed by human beings.

Pest situations spread because of transportation improvements. Improvements of public and private transportation give rise to the spreading of endemic pests to other regions, "with the many forms of modern transportation, insects are no longer limited in their dispersal capabilities by natural geographic barriers such as mountains and oceans, but are carried about as hitch hikers (Romoser 1994, p.396)."

Additions to that, transportation improvements catalyze the growth of pest situations. When an exotic insect is introduced to a region away from its ecological nemeses, it would bring destructive results. An example is the European corn borer which became a major corn pest in the United States but only a minor one in its homeland (Fronk as cited by Romoser 1994, p.396).

Lastly, pest situations appear because of human attitudes and demands. Human attitudes and demands may result to a pest problem or may greatly overstate a minor one.

People only want blemish-free produce thus when a very slight manifestation of insect damage will drastically affect the economic value of the vegetable or fruit although its quality was never really changed. This mentality is often referred to as cosmetic effect.

Furthermore, "many insects are considered to be pests not because they attack us or destroy any of our goods but simply because we find them distasteful (Romoser 1994, p.396).

Based on its ecological origin, insect pest situations were never present but only evolved because of the dominant control of humans to natural resources.


Pest situations are not naturally occurring and all human-made. These happen because as advancements in human lives happen, they tend to intrude the natural balance of other animal lives such as insects. These factors are the improvements of agriculture, emergence of modern transportation, change in human attitudes and demands. Pest situations also occur because of habitat expansion of humans forcing insects to live with them and agricultural discoveries lure insects to attack a dense collection of food propagated by humans.