INTRODUCTION

1. INTRODUCTION Humans and insects • share the same world and interact intimately • Interaction could be described as • the closest between two animal groups • direct or indirect with reference to man • either beneficial or detrimental to man • inevitable and forced most of the time • Thus insects can be described as inevitable and formidable neighbor of man

2. Reasons for the intimacy in human-insect interaction • Remarkable and unequalled species diversity: Insects being at least 75% of the total number of animals described thus far (more than X3 of all other animal groups) remain an unbeatable group in terms of diversity. Dipteran types alone being more than all vertebrate types and coleopterans more than all invertebrates other that insects. This remarkable diversity ensure that a reasonable number of arthropods share same ecological niche with man, interact directly or indirectly with him or produce something valuable to him • Enormous and tumultuous insect population sizes: Insect numbers anywhere they occur are usually intimidating and readily noticeable. Attempts to estimate insect populations are usually beset with great difficulties occasioned by the excessively large numbers and great riotous mobility. Thus man who see himself as the most important species is always threatened by their presence in large numbers. He is usually very conscious of this fact and he recons with it in his deals with the insect

3. Reasons for the intimacy cont’d • Ubiquitous nature of habitat colonization: The occurrence of one insect or the other in virtually all locations and the fact that such insects have over time become strongly adapted to such environment remains fascinating to man. He is therefore forced to agree with the fact that insects are founding members of any community he intends to join and he is forced to relate with them. • Unlimited range of organic food: All forms of organic materials available within the ecosystem have at least one insect specialist consuming it. This to a large extent supports diversification and biological success of the group; a feature that readily bugs man when his interest is at stake but encouraged when his wastes are involved. Man being a strong dependent on organic substrates therefore see insects as persistent competitors

4. Reasons for the intimacy cont’d • Ability to make do with small food resource: Due to their small size and short life span insects do exceptionally well in terms of growth and reproduction utilizing a resource that is assessed as small by man. A cup of beans that may just fill man as his meal at a sitting will raise more than 500 weevils over three generations. Man recognizes, abhors but has accepted this as a challenge he always tries to tackle. • High regenerative and establishing rates: The rate of increase in insect population number after their appearance frequently fascinates man. Insects attain alarming and readily noticeable number within a short period of time. Man’s swift reaction to insect incidence or incursion is informed by this subconsciously borne fact. • High motility and dispersal rates: Insects ability to fly coupled with jointed limbs that have undergone various modifications aimed at improved functional efficiency gives them a viable and proficient leverage that enhances their distribution and active escape defense activities; both of which continues to interest man.

5. Reasons for the intimacy cont’d • Improved response and defensive abilities: Irritability and communication in insects aretwo spectacular lines that have witnessed tremendous advancements and have contributed enormously to the survival of insects. These have not only improved their survival instincts, as they are capable of responding to virtually all environmental alteration even when minute, but has ensured improved and effective defenses that remains challenging to man. • Enhanced survival rates with varying life forms and cycles: Insects present varying cycles and developmental stages that often require devotion to unravel. In most cases, particularly in those with complete metamorphosis, the stages have conspicuously dissimilar ecological niches that vary with insect type and favor the survival of each individual type. • Ability to tolerate wide range of environmental alterations: Insects have over time evolved adaptive features that ensure tolerance of alterations in their natural environments. To discourage them therefore man requires a level of alteration that is often beyond natural limits requiring extra cost to establish and beyond human tolerable limit too.

6. INTRODUCTION CONT’D Generally • Insects and man utilize the same abiotic environments to achieve their biological desires • Most of the time these abiotic components are adequate for the two but either of them, especially man, complain of the others (insects) activities • The insects seems to be doing better than man and man seems to need some help • Man therefore seek to solve some of the problems initiated by insects while encouraging the beneficial interactions using ecological information obtained from entomology in a study or approach termed Applied Entomology.

7. Applied Entomology • The interactions between man and insects seem to have improved the survival capability of insects and pose so much challenge to man • Man, recognizing this has put up and put in so much aimed at exterminating the insects but this have proved abortive, instead it has empowered the insects • Unfortunately the insects seems to utilize resources better than man in terms of • getting at it earlier, • multiplying faster, • concealing damage, • soiling the resource and • reducing its value. • These give an impression that insects have come to stay and that man may probably be living in an insect world. • Man therefore has always been in search of avenues to remove these challenges and the solution lies in Applied Entomology: a managerial science that entails exploiting the biotic interrelationship between man and insects to man’s advantage. This involves understanding insect ecology, i.e. their responses to abiotic and biotic factors in their environments, managing them, and taking advantage of them to please man.

8. Interactive ways Abiotic factors Other Biotic agents Humidity Insects pH temp humidity Humans O2/pH space Temp/O2 Food/space food

9. Ecological interactions in Applied Entomology In applied entomology attempts are made by man to reduce the negative impacts of insects by Destroying or killing insects identified to be working against human interest but this has been condemned Discouraging insect patronages that have direct impact on man Discouraging insect patronage of biotic agents of interest to man Discouraging insect patronage of abiotic components that are useful to humans Discouraging insects generally by adjusting abiotic conditions Encouraging insects identified to be beneficial to man Destroying/Discouraging and encouraging insects are mostly achieved by manipulating the abiotic and biotic situations around the insects. To do theses effectively there is a need to understand insect ecology

10. Insects and ecological factors • The various factors affecting insects can be categorized into three on the premise of limit of tolerance • These include: • Minimum factors: These include factors that affect insects adversely only at the lower limit, e.g. space, food, O2 availability, etc.. • Maximum factors: Those factors that affect insects adversely only at the upper limit, e.g. biotic factors such as competition, predation, parasitism, etc.. • Minimum and maximum factors: In this case the factor affects the insect adversely at both minimum and maximum limits, e.g. temperature, humidity, light, pH, population density, etc. Fortunately for insects natural variation range of these factors are within tolerable limits and do not last long.

11. Era in Insect life History The life history of a typical insect has three era, i.e. • Pre reproductive era (period prior to adulthood) i.e. duration of immaturity during which growth is usually experienced. This period is frequently relatively longer in most insects. In paedogenetic forms where immature forms engage in reproductive activities it is even longer. • Reproductive era: i.e. period after the former when the insect initiates reproductive activities that includes mate searching, courtship, mating and egg laying. It varies considerably amidst insects, as it may last few hours in some moths and mayflies and weeks in others like the beetles. The most varied being the oviposition (egg laying) duration, as some insects lay eggs at one sitting, e.g. moths, while others lay numerous eggs singly over several weeks, e.g. housefly and some over several months e.g. beetles. • Post reproductive era: i.e. period after oviposition. This is usually a narrow period, as most insect soon die after ovipositing. Some insects, however, undertake several cycles of reproductive activities with short breaks in between before death, thus they combine and prolong the last two era.

12. Life cycles • Insects present three basic forms of cycles: • Univoltine : a single complete life cycle or generation with a glaring break in a year, e.g. The pallid emperor moth, Cirinaforda. Eggs are laid in May/June, larvae are noticed ravaging sheabutter leaves between June and August, by September they pupate and emerge nine months later (April/May) and adults live for 72 hours. • Multivoltine: More than one complete cycle or generations in a year. Two types are recognized: i) Homodynamic type: produce numerous successive generations throughout the year without interruptions since environmental condition is favorable throughout the year. ii) Heterodynamic type: they have many generations in a year but they go through a break at a point in the season • Perennial: One complete life cycle in longer period than a year, e.g. the cicada, which takes 13 to 17 years to emerge after completing one cycle or the mayflies that emerge after two to three years

13. Insects and environmental sensitivity • Insects demonstrate a fascinating and complex degree of sensitivity to their environment • This they do so well that they are hardly caught unaware • They achieve this fete by adjusting their ways in the following respects: • tolerance level improvement • developmental rate adjustment • life span and cycle adjustment • fecundity rate, etc. adjustments Understanding some of this will go a long way to assist in their effective management

14. Tolerance level improvement • Environmental conditions of insects are rarely optimal at all times. • Insects therefore frequently face the challenge of coping with the challenge and this they achieve by tolerating the alterations • Fortunately for insects they seem to have worked on this over a prolong period of time and have evolved behavioral and physiological adaptations that enable them cope with the natural fluctuation range of these factors • Some of these behaviors include diapausing, migration, hibernating, etc • In insects with varied life stages some of the life stages of the insect are more susceptible to the alteration than the other. Hence insects frequently modulate their life cycle to encourage the occurrence of the more tolerant stage when the harsh situation is most likely to occur. • The variation of the factors are therefore usually within the tolerable limits of the insects and do not last long. • Most insects therefore experience prolonged exposures that does not result in desirable control under natural situations

15. Tolerance level improvement • To achieve an insect control mode therefore artificial means that go beyond natural limits are usually required and employed. • The length of time an insect can tolerate an adverse condition is inversely proportional to the intensity of the condition, hence both intensity and duration of exposure plays a paramount role in the efficiency of such exposures. • insects that survives exposures to situations beyond tolerable limit over time and generation develop resistance against the instituted control mode • This ensure they come out stronger and the ability is sustained across generations A Verse knowledge of insect tolerance styles to the various environmental factors is therefore fundamental to the design of an effective control measure, since killing of an insect is achieved by creating a condition beyond the tolerance level of the insect but this must be well managed otherwise it produces insects that will not only overcome the situation but will come out stronger and equipped to survive

16. Developmental Rate adjustment • Insects develop better within low range of environmental changes. • They are known to be sensitive to humidity, light and particularly temperature being poikioterms or ectoterms • Light (Photoperiod): Longer days have been shown to encourage continuous and faster development while shorter days promote diapauses and inactivity. Thus longer day encourage metamorphosis and prolong the activity of diurnal insects but the reverse may be the case with nocturnal insects. • Humidity: This factor usually has a pronounced effect on the immature stages and it goes a long way to determine the survival of the egg and pupal stages of most terrestrial insects. More so since these stages do not feed and therefore do not have avenue for water replacement. • Temperature : Reduced developmental rates results from variation above and below a certain acceptable narrow range due to reduction in metabolic activity (Fig 1a- Metabolic activity against temp) • further reduction or increase beyond the narrow range witnesses cessation of activity and lethal responses (Fig 1b - Developmental rates against temperature) .

17. Developmental Rates cont’d • A plot of the metabolic activity or developmental rate against temperature (Fig 1a) revealed that there is a minimum temperature for development to take place in an insect • This temperature is known as Threshold Temperature (TT) and it varies with insect species.  • Rate of development in insects is informed and proportional to the difference between the threshold temperature and the prevailing environmental temperature, i.e. Effective Temperature (EF) provided EF is within the active range, i.e. > TT and < ML • A particular insect therefore takes a fixed time to undertake a development at a particular EF a concept known as Thermal constant theory • This concept • Is 250 year old • is used to monitor and predict biological events in form of developments in poikioterms. • has several methods the most popular and comprehensible one being the Day-Degree method.

18. Developmental Rates cont’d The Day-Degree method assumes that: • An insect require to accumulate a fixed amount of heat (thermal constant) for a particular development to take place • the insect acquires or accumulates a fixed amount of heat, i.e. (EF-TT) for development daily • such developments are actualized when the heat accumulated totals up to the fixed amount required, i.e. Thermal constant(TC) for the development. • The unit for heat accumulated is Day-Degree or DD or 0D and Thermal Constant (TC) is DD/0C • Thermal constants and TT vary amongst insects and hence must be determined per insect species.

19. Thermal constant and Threshold Temperature determination • Several methods could be used • It is easily achieved by • Correctly identifying the insect and development of interest • Insects that are set but yet to initiate the development are collected • Introduce the insects into series of controlled chambers set at different but regularly increasing temperatures at the same time • noting the duration of actualizing development in the various chambers accurately • Compute the average time per the various temperatures of exposure • A plot of time of the development against temp shows a regression line with TT as the point of intercept with the abscissa • The thermal Constant (TC) is computed as a mean of means of the product of the difference between the temperature of exposure and TT and the duration for the development at that temperature, i.e. TC = (EF –TT)Duration

20. Day-Degree method cont’d • computation of the of the average daily temperature on the field is cumbersome • Quite a number of procedures have been proposed but the easiest of them is the simple average method • Here a mean of the maximum and minimum daily temperatures is used with the following guiding conventional rules to minimize errors: • When maximum temperature is below TT, no heat is accumulated • When maximum temperature is above TT but minimum is below it, the minimum should be set at TT for average calculation. • When maximum temperature goes beyond the point of cessation of activity it should be set at the point of cessation (ML)

21. Shortcomings of Day-Degree method: • It does not take surface temperature that may be slightly different from environmental temperature into cognizance • Insects that bask or retire to shade are not taken care of • An average that gives an EF below TT is erroneously assumed not to have accumulated heat for the day • Soil insects and their environmental temperature are wrongly assessed

22. Life span and cycle adjustments • Insects modify their life span and cycles to cope with challenges they face in the ecosystem. • The fact that life cycle shows a cyclical pattern, suggests an implicates genetic factor playing a role in the change within the population and this has been largely linked to the brain and biological clock of the insect that regulates metamorphosis. • Some of the frequently noticed challenges include: • food availability and sustenance, • differential growth rate created by the different diets especially in perennial forms, • Environmental/abiotic factor variation and • Easy and open access to humans • proneness to human negative responses, etc.

23. Life span and cycle adjustments Responses Insects respond to challenges occasioned by alterations of their environmental factors by • enhancing and improving fecundity rate • Taking to flight • Assumming a quiscent mode They also modify their life span to enable their survival in the face of the alterations by • a univoltine insect may change to a multivoltine form in cooler or humid climate. Such situations have been exploited in the encouragement of beneficial insects and discouraging insect pests. • a univoltine insect may change to a perennial, e.g. some insects are known to respond this change by way of prolonged dormancy that ensure their generation last more than a year, • A homodynamic may change to heterodynamicmultivoltine or vise versa when an unfavorable or favorable situation arises

24. Life span and cycle adjustments • They also adopt a life cycle that ensure their survival in the face of the change. • Insects frequently respond to these challenges by • Modifying the highly noticeable insect stage that will usually require prolong timing to a form that will • concealed damage • less noxious and most tolerable • No longer enjoy prolonged duration • Be less conspicuous and hidden • relatively inconsequential These examples are easily noticed with mosquitoes, weevils, housefly and lepidopterans. A good knowledge of the length of these eras in different insects is significant, as the noxious stage may not usually be the most auspicious stage for attack. Accessibility and duration of availability matter count more.

25. Fecundity • Describes the number of eggs laid per female and it is unique per species and dependent on the food situation and environmental conditions • This factor ensure that insects keep up their numbers and perpetuate themselves • Insects increase their fecundity when they are supported by the environmental factors and even better when they feel threatened and • such increases though sounding inconsequential can be colossal, e.g. an insect that lays 4 eggs, 50% of which develop into female adults will exceed 1 million population number in 20 generations, but if under a stringent condition it decides to respond by producing more eggs to the tune of 200 eggs, the same I million mark will be reached in 3 to 4 generations.

26. Conclusion These various modifications/adjustments/adaptations put up by insects have empowered them so much in respect of human efforts at controlling them, as they ultimately culminate in the advent of an improved, resistant and constantly evolving insect community with an overall consequence of improved survival capability and giving an impression that insects are uncontrollable. Thus constituting a serious and seemingly insurmountable challenge to entomologists