CHAPTER ONE

INTRODUCTION AND LITERATURE REVIEW

1.1 :

Adult parasitoids are free-living and may be predaceous. They lay theireggs inside their hosts. The larval stages which hatch from the eggs developwithin a single host, ultimately killing the host. This is whyparasitoids are valued as natural enemies biological control agents. Parasitoids are often called parasites, but the term is more technicallycorrect. Most parasitoids are or flies, althoughsome rove beetles (see Predators) and other may have lifestages that are parasitoids. (Hoffmann, 1993).

Most insect parasitoids only attack a particular life stage of one or severalrelated species. The immature parasitoid develops on or within a pest, feeding on body fluids and organs, eventually leaving the host to pupateor emerging as an adult. The life cycle of the pest and parasitoid can coincide, or that of the pest may be altered by the parasitoid to accommodate its development.

The life cycle and reproductive habits of beneficial parasitoids can be complex. In some species,,only one parasitoid will develop in each pest while, in others, hundreds of young larvae may develop within the pest host. Overwintering habits may also vary. Female parasitoids may also kill many pests by direct feeding on the pest eggs and immature stages.(Hoffmann, 1993).

1 Majorcharacteristics of insect parasitoids:

• They are specialized in their choice of host

• They are smaller than host. • Only the female searches for host. • Different parasitoid species can attack different life stages of host. • Eggs or larvae are usually laid in, on, or near host. • Immatures remain on or in host; adults are free-living, mobile, and may be predaceous . • Immatures almost always kill host.

1.1.1. Relative Effectiveness:

Whereas insect predators immediately kill or disable their prey, pestsattacked by parasitoids die more slowly. Some hosts are paralyzed, whileothers may continue to feed or even lay eggs before succumbing to the attack. Parasitoids, however, often complete their life cycle much more quickly and increase their numbers much faster than many predators. Parasitoids can be the dominant and most effective natural enemiesof some pest insects, but their presence may not be obvious. It is oftennecessary, to determine the extent of parasitism, to dissect or rear samplesof pest insects to see if any adult parasitoids emerge.

Parasitoids can be parasitized by other parasitoids. This phenomenon, knownas hyperparasitism, is a natural occurrence, can be common, and may reduce the effectiveness d'f some beneficial species. Little can be doneto manage hyperparasitism.

2 1.1.2.Superfamily Ichneumonoide:

The Ichneumonoidea is a very large and important superfamily of the order . Its members are generally small insects, which are all parasitoids. The females are characterized by having long ovipositorsspecially those species whose hosts feed deep in plant tissues. Thereare two families: the Barconidae and the and both arevery important in natural and biological insect pest control. Members ofthese two large families are very similar and cannot be distinguished in the field. Their hosts include many insect orders as well as spiders and pseudo-scorpions. However, lepidopteran caterpillars are the most importanthosts of both ichneumonids and braconids. A few species are hyperparasitesof other parasitic species. Most ichnneumonids are endoparasites and they lay their eggs commonlyin or on the larval stage of the host. Generally the host does not develop beyond the larval stage and is prevented by the ichnneumonid hyperparasite from reaching the adult stage. Oocenteter (Ichnomonoidae) and Chelonus (Barconidae) both complete their developmentin the larvae of Diplazon which may lay its own eggs in that of its hover-fly host and the adult ichneumons emerge from the fly pupanum. Ichneumons rarely attack adult insects but may ovipositin adult beetles and attacks adult Ichneumonidae. Each parasiteis adapted to its host, e.g. the egg of many endoparasitic species ofBaraconidae is remarkabll for its increase in volume within the host. (Askew,1973) .recorded a one thousand-fold increase in volume of the eggof (Pertitus coccinellae) before hatching of the first instar . Such an increase could only be allowed by an exceeding elastic chorion and this also permitted the deformation of eggs of many Ichneumonidae duringoviposition.

3 1.1.3.Family Ichneumonoidae (Ichneumonid wasps): This is a very large group of species many of which parasatise otherinsects. Different species of ichneumonid can attack a single host species. The larvae of Lepidoptera, beetles and saw flies are the most commonlyattacked hosts. Ichneumonoidae are very important in natural biologicalcontrol of many plant pests. Rhyssapersuasoria

An example of the Ichneumonoidae is Rhyssa persuasoria, which is the largest British ichneumonid with a body length of four to five centimeter and an equally long . Its host is the larva of the wood- Sirex gigas that borrows in coniferous wood. The full length ofthe ovipositor, with its sharp and cutting apex, is required to reach and enterit through the wood by pressure and movement of the abdomen. The whole procedure of egg-laying may take about thirty minutes. At the time of egg-laying, Sirex injects spores of a symbiotic fungus into the wood and the fungal hyphae fill the burrow of the wood-wasp larva and the surrounding wood. A substance present in this fungus, guides Rhyssa to its host frass, which is very attractive to Rhyssa, specially, the fresh frass produced by a fully-grown wood-wasp. The following three species are members of this family and are parasitoids on pests,of crops in the Sudan: J- Microdus sp on Earias insulana.

2- Pristomerus sp on Earias insulana

3- Paniscus opaculus on Achaea catella Guenee.

4 Ichneumon wasps reach body lengths of ten to fifty millimeters. The colourationof their bodies varies .. The basic colour is often black or reddish-brown.Many species have markings in red, white, yellow or brown.The antennae of most species have more than sixteen segments. Thepresence and shape of the areole in the front wings is a major identifyingcharacteristic. The females of many species have a long ovipositor.The abdomen is clearly separated from the front part of the body.(Aubert, 1969).

Thefemale usually has a long ovipositor which is used to insert eggs intothe host's body. In some species the ovipositor is longer than the female'sbody. The length of the ovipositor allows the female to inject her eggs into hidden hosts such as leaf-rolling or stem-boring caterpillars.

(Aubert, 1969).

Some species lay eggs externally and attack the host frml1. outside. Th.e host will usually survive when the larvae are still living. When the larvae are fully grown, they either pupate inside the dead host or form a

. cocoon outside. (Aubert, 1969).

,

5 D Figl(a): Ichneumonoid ( LonJ Ovi poSI1 ()

Figl(b): Female oflchneumonoid .

6 Figl (c). Male offig wasp (LJ~Le~s)

7 .....•••,.~~------

1.2. Ficus sycamorus:

Ficus sycamorus, called the sycamore fig or the fig- mulberry (due to the leaves' resemblance to those of the sycamore, or sycomore, is a fig species that has been cultivated since early times. (Note that the name sycamore has been used for a variety of plants.) Ficus sycomorus is native to Africa south of the Sahara. It also grows naturally in the southern Arabian Peninsula and in very localized areas in Madagascar, and has been naturalized in Israel and Egypt. In its native habitat, the tree is usually found in rich soils along rivers, but also in mixed woodlands.

Ficus sycamorus grows to twenty meter tall and sixteen meters wide with a dense round crown of spreading branches.

The leaves are heart-shaped with a round apex, fourteen centimeters long by ten centimeter wide, and arranged spirally around the twig. They are dark green above and lighter with prominent yellow veins below, and both surfaces are rough to the touch. The petiole is point five to three centimeters long and pubescent.

The fruit IS a large edible fig two to three centimeters III

diameter, ripening from green to yellow or red. They are borne III thick clusters on long branchlets or the leaf axil. Flowering and fruitingoccurs year-round, peaking from July to December.

The bark is green-yellow to orange and exfoliates III papery strips to reveal the yellow inner bark. Like all other figs, it contains latex. (Zohay and Hoff, 1993).

8 The fig Ficus sycamorus reqUIres the presence of the symbiotic wasp Ceratosolen arabicus to reproduce sexually, and this insect is extinct in Egypt, (Zohay and Hoff, 1993). They have no doubt that Egypt was "the principal area of sycamore fig development." Some of the caskets of mummies in Egypt were made from the wood of this tree. In tropical areas where the wasp IS common, complex mini-ecosystems involving the wasp, nematodes, other parasitic wasps, and various larger predators revolve around the life cycle of the fig. The trees' production of fruit in such environments assures its constant attendance by the insects and animalswhich form this ecosystem (Zohay and Hoff, 1993).

1.2.1Gall Flowers In Figs:

Although some authors refer to the "fruit-like" structures on wild fig trees (Ficus) as galls, they are actually specialized structures called syconia bearing minute male and female flowers on the inside. A tiny female wasp enters an opening known as (ostiole) on the syconium to pollinate the flowers and lay her eggs inside the short-style female flowers. She inserts her ovipositor down the stylar canal and deposits an egg inside the ovary of each short-style flower. According to Condit, \ 1947), oviposition injures the stylar canal, thus inhibiting pollen tube growth and fertilization in short-style flowers. Because her ovipositor is too short, the fig wasp is unable to oviposit inside the long-style flowers. The latter flowers each develop a seed (with an embryo and endosperm) by normal pollination and double fertilization. Although there IS considerable disagreement in the literature, many authors continue to describe the short-style flowers as "gall flowers," presumably because

9 they are commonly occupied by a developing male or female fig wasp; however, they are fully capable of producing normal seed-bearing drupelets, and in this respect are no different from long-style flowers. In two to three months a new crop of male and female wasps emerge from the short-style flowers. After insemination by males, the fertile female wasps pack their pollen baskets with pollen and exit the syconium. These syconia produce seeds inside long-style flowers that provide the vital genetic diversity and perpetuation of fig trees.

1.2.2.Syconia of Ficus sycomorus:

The syconia of Ficus sycomorus are not galls. They are fleshy structures lined on the inside with hundreds of tiny male and female flowers (Fig). They are essentially an inflorescence. The inflorescence is formed of two types of flowers: short-style flowers on the inside and long-style flowers to the outside. A certain wasp Sycophaga sycomori does not pollinate the flowers but lays eggs inside the short-style flowers. The process of oviposition and the presence of nonpollinator wasp larvae not only initiate the development of endosperm tissue, but also the enlargement and ripening of the syconium. Thus the entire syconium could be viewed as a gall occupied by nonpollinator wasps.

The long-style flowers are pollinated by another species of wasp \ Ceratosolen arabicus According to Galil (1977), in its native habitat of eastern Central Africa and Yemen, F. sycamorus is pollinated by the wasp Ceratosolen arabicus, and the long-style flowers produce seeds.

10 Fig 2(a):Fruit or syconium

Fig (2)b:Wasp inside the syconium

11 Fig2 (c): Ficus sycamorus ripe fruits

Fig(2)d: Ficus sycamorus green fruits.

12 Fig2 (e ):Ficus sycamorus Oestium.

t

Fig2 (f): ostioium of Ficus sycamorus

13 1.3. Parasitoids:

Parasitoids are insects with a parasitic larval stage that by feeding on the body of a single host insect or other . Feeding by the larval parasitoid invariably results in the death of its host, and the resulting adult parasitoid develops is a free-living insect. Thus parasitoids occupy an intermediate position between predators and true parasites. In contrast to parasites they kill their host like a predator, but in contrast to predators they require only a single host to complete their development, as is the case for parasites. Nearly 100/0of described insect species are parasitoids and, as they often belong to poorly known groups of insects, it has been suggested that they are more likely to represent 20-25% of all insect species. Since the first accounts of insect parasitism at the beginning of the 18th century, parasitoids have attracted considerable attention because of their potential to regulate the abundance of insect hosts in both natural and managed ecosystems.(Mills, et. al., 2003).

Numerous insect pests have been effectively controlled through releases of insect parasitoids in biological control programs around the world. Although not always applicable or successful, biological control continues to provide some dramatic examples of sustained long-term control of invasive insect pests. As a result, of the research conducted through biological control programs, parasitoids have also become important model organisms for the study of ecology, behavior, and evolution.(Godfray et al,1994).

14 1.3.1.0RIGIN AND DIVERSfl'¥ OF PARASITISM:

About 74% of the known parasitoid species belong to the parasitic Hymenoptera, an arbitrary division of the suborder

Apocrita of the order Hymenoptera. It is generally believed that parasitism evolved just once in the Hymenoptera and that the together with the family Orrusidae form a holophyletic group that includes all of the known parasitic wasps. Although the larvae of some species may initially feed on microorganisms in the tunnels of wood- boring insects ,the young larvae of others feed externally and subsequently internally on larvae of the borers themselves. Many and wood wasps (sawfly superfamily ) carry symbiotic fungi in pouches located at the base of the ovipositor

(mycangia) that are inoculated at oviposition, allowing the larvae to feed on infected and partially digested wood. However, not all siricoids carry fungal symbionts and some may have evolved to kill those that did and subsequently feed on the more nutritious dead insect rather than the wood. This trait is seen among the present-day orrusids. Within the parasitic Hymenoptera there are close to 64,000 described species of parasitoids in ten super families "that are, with rare exception, exclusively parasitic However, parasitoids are also known from five other insect orders. In contrast to the Hymenoptera, parasitism has evolved repeatedly within'these orders, from a fungal-feeding (e.g., Rhipiphoridae), dead- organism-feeding (e.g., Phoridae, Sarcophagidae), predatory (e.g., Carabidae, dipteran families), or phytophagous (e.g., Lepidoptera) ancestor. For example, parasitism is estimated to have occurred twenty one times in the Diptera, producing nearly 15,000 described parasitoid species, and fifteen times in the Coleoptera, producing a further 3400

15 parasitoid species Parasitism is unusual and rare among the remaining three orders.

1.3.2.PARASITOID LIFESTYLES:

Parasitoids are frequently categorized as having larvae that are either ectoparasitic (external feeders) or endoparasitic (internal

feeders) and either solitary (one per host) or gregarious (several per host) in their development. However, a more useful categorization of the lifestyles of parasitoids is the dichotomy between idiobiosis and koinobiosis. Idiobionts paralyze and/or Parrest the development of a host at oviposition, providing their Larvae with an immobilized static resource on which to feed. In contrast, koinobionts allow the host to continue to feed and/or develop after oviposition, such that their larvae feed on an active host that is killed only at a later stage. Although ectoparasitism and endoparasitism are distinct modes of parasitism, the separation of idiobiont and koinobiont lifestyles is less clear. There should be no problem in correctly categorizing parasitoids that attack an active stage of the host life cycle (larva or adult) or those that allow a transition between life cycle stages of the parasitized host (egg-prepupal and pupal-adult parasitoids). However, the distinction is not always so obvious for parasitoids that attack and complete their development in an inactive stage of the life cycle (egg or ). f 1.3.3.Idiobionts:

Idiobiont parasitoids frequently attack hosts that are concealed in plant tissues or exposed hosts that provide some other form of physical protection, such as the scale covering of armored scale insects. Thus, many have long to reach their concealed hosts and strong

16 mandibles to escape from concealed locations. The majority of idiobionts that attack concealed hosts have larvae that are ectoparasitic and feed on hosts in the later stages of their development. An ovipositing adult first injects a venom into the host, to induce temporary or permanent paralysis, and then oviposits on or near to the immobilized host. In a few cases (some , , and in the Hymenoptera), the parent female remains with the parasitized host either to defend her young offspring against competitors or hyperparasitoids or to ensure continued paralysis of the host. Ectoparasitic idiobionts are often long lived, feeding for somatic maintenance on honeydew, nectar, or other plant exudates. They are synovigenic, meaning that they continue to mature eggs throughout adult life and prod large yolk-rich eggs by using nutrients gained from host feeding (see below). Consequently, ectoparasitic idiobionts have a relatively low rate of host attack and a low fecundity. The hatching larvae are protected from desiccation by the host concealment, but develop continuously and rapidly to consume the host before it is attacked by scavengers or microbial decay. Endoparasitic egg and pupal parasitoids are also considered to be idiobionts, although as noted above, this categorization is less clear. In this case the hosts are frequently exposed rather than concealed, and in place of paralysis, development of the host appears to be arrested by secretions either from the ovipositing adult (egg parasitoids) or from the young larva (pupal parasitoids). Endoparasitism of host eggs is facilitated by the lack of an immune defense, but it is not known how pupal idiobionts avoid such defenses in their hosts. The absence of an intimate association between the juvenile stages of an ectoparasitic idiobiont and its host allows this group of parasitoids to have a broader host range, using a variety of hosts that share a common habitat or host plant. Some endoparasitic idiobionts are more restricted in the host range, however, perhaps because of a need

17 for more specific cues in host recognition or for detoxification of the chemical defenses of exposed hosts.

1.3.4.Koinobionts:

All dipteran parasitoids, the majority of coleopteran parasitoids, and many hymenopteran parasitoids adopt a koinobiont way of life. Koinobiont parasitoids attack both exposed and concealed hosts, and the majority of species have endoparasitic larvae. Endoparasitic koinobionts attack a broad range of developmental stages of their hosts. Access to concealed hosts is facilitated either by attacking the more accessible egg or young larval stage of their host (hymenopteran koinobionts only) or by production of a free-living first instar that can complete the location of a suitable host. Koinobionts typically oviposit into the body of their hosts with minimal disruption to the normal activity of the host. The hemocytic immune response of the host can result in the encapsulation of parasitoid eggs and larvae and is a significant obstacle to endoparasitism.

Parasitoids are known to be truly aquatic, using their legs or wings swim through the water to locate submerged host eggs. Parasitoid load is determined by a combination of phylogeny, feeding niche, abundance, and chemical defense. The absence of a pupal stage greatly reduces the parasitoid load of host, but even among the holometabolous insects, beetlesconsistently support far fewer parasitoids than the importance of host'phylogeny. The feeding niche of a larval host also has an important influence'on parasitoid load, being greatest among those hosts that have restrictedmobility and poor protection (e.g., leafminers, case bearers ) and reduced either by greater mobility (e.g., external feeders) or by greater protection(e.g., borers). The greater the abundance of a host the greater itsparasitoid load, because a number of less specialized parasitoids and

18 even incidental species are able to make use of an abundant resource. Then, finally, the sequestration of defensive plant chemicals by externally feeding host larvae appears to offer a further line of defense that can lead to a reduction in parasitoid load. (Resh et al,2003).

It has frequently been suggested that parasitoid diversity declines from temperate zones to the tropics. Such a pattern is evident for the very species-rich superfamily the Ichneumonoidea (Ichneumonidae and Braconidae), but is not upheld among the Chalcidoidea. Nonetheless, the decline, or absence of an increase, in overall parasitoid diversity in the tropics is an interesting anomaly in comparison to the increase III diversity of their insect hosts in the tropics. An increased level of predation the abundance of each host species due to fragmentation of resources, and a greater availability of plant-based chemical defenses for host insects to use for protection may all help to account for this anomaly. (Resh et al ,2003).

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