Insect ecology
[5][6][7] Insects play significant roles in the ecology of the world due to their vast diversity of form, function, and lifestyle.
They are the major contributor to biodiversity in most habitats, except in the sea, they play a variety of important ecological roles in the many functions of an ecosystem.
In the case of nutrient recycling, insects contribute to this vital function by degrading or consuming leaf litter, wood, carrion and dung, and by dispersal of fungi.
Insects form an important part of the food chain, especially for entomophagous vertebrates such as many mammals, birds, amphibians, and reptiles.
Typically, some species of fly are the first to feed on the dead body, but the order of insects that follow is predictable and is known as the faunal succession.
There is even a species of dung-beetle that will roll feces into a ball, push it into a pre-dug hole, lays egg in the dung, and then covers it with fresh dirt to provide a perfect nursery for its larvae.
Predatory insects are typically larger as their survival is dependent upon their ability to hunt, kill or immobilize, and eat their prey.
They often have specialized mandibles (mouthparts) for this task, some causing excruciating pain, paralysis, or simply having a high bite force.
Parasites vary widely in how they survive in or around their hosts; some complete their full life cycle within the body, such as the females of most Strepsiptera species, while others may only stay in for the duration of their larval stage.
A kleptoparasite may opportunistically feed on prey that has been recently killed by a predator, such as many adult freeloader flies, or it may deceptively live in the host's nest, such as the majority of the ant crickets.
These species transmit viruses, disease, and even other, smaller parasites to the host, spreading these throughout the populations of many third world countries with poor health care.
[17][18] The majority of parasitoids insects consume their victims as larvae, while the adults often feed on nectar or other organic material.
A visual cue could simply be the outline of a certain type of leaf, or the high contrast between the petals of a flower and the leaves surrounding it.
The olfactory cue could be the scent of the nectar produced by a flower, a certain chemical excreted to repel unwanted predators, or the exposed sap of a cherry tree.
[11] After a herbivorous insect is finished feeding on a plant, it will either wait there until hungry again, or move on to another task, be it finding more food, a mate, or shelter.
Some diseases even produce a sweet smelling, sticky secretion from the infected plant to attract more insects and spread farther.
Both pleiotropy and epistasis have complex effects in this regard, with the simulations of Griswold 2006 showing that more genes provide the benefit of more targets for adaptive mutations, while Fisher 1930 showed that a mutation can improve one trait while epistasis causes it to also trigger negative effects - slowing down adaptation.
They also present some divergent examples, both delayed response – suggesting that food decisions were mediated by cognition and not just simple chemoreception – and unequal chemoreceptor stimulation – with gustatory cells firing equally when presented with any material, but deterrent cells firing to a greater degree for undesirable materials.
They find Manduca sexta's habituation to salicin to be cognitively mediated because deterrent sensory cell stimulation barely decreases even when avoidance ceases.
On the other hand Glendinning et al 1999 finds M. sexta habituation to caffeine to be due to change in chemoreceptor activation because it decreases significantly, and at the same time as cessation of feeding avoidance.
al 2011 finds no change in distribution in one example, but instead the same herbivore switched primary hosts due to altered flowering time.
[29] Recent behavioral studies on symbiont-infected and uninfected insects have shown that not only parasitic or pathogenic microbes but also commensalistic and mutualistic microbes can influence the host’s behavior in ways that seem adaptive and these symbiotic interactions can often shift from one form to another due to external factors or internal changes driven by the symbionts themselves.
[33] A specific example of such interactions is bacteriocyte-associated symbionts, which are passed directly from mothers to their offspring during the early stages of egg or embryo development.
For instance, in some cases, insects may engage in symbiotic relationships where one species benefits while the other is unaffected, this is known as commensal symbiosis.
The insect-symbiont interactions generate morphological adaptations and mechanism that insects use to protect, nourish, and transport their microbial partners.
The attraction of ambrosia beetle to its fungal symbionts indicate that some signaling by microbial volatile organic compound s(MVOCs) produced by the fungi leads to this partner choice.
[40] Since aphids’ diet of plant sap lacks certain essential amino acids and vitamins, Buchnera supplies these nutrients to them.
[43] In terms of inquilinism, insects commonly establish themselves in human garages or shelters of other animals for protection against predators and weather.
Micro-evolutionary changes include shifts in genome and alleles while macro-evolution is the emergence of a new species, also called speciation.
These roles include pollination, seed dispersal, improving soil fertility, act as a source of food for other organisms and involve in disease transmission.
