Bio 355 Lecture 19 December 1, 2004 1

Insect predators and parasites Introduction Many species of insects eat other insects or arthropods Some species generalize and eat a broad range of species Many species are specialized, however, and their importance may be underestimated Some predators oligophagous, some may even be monophagous Predation has arisen multiple times in insects Parasitism as well

Kinds of predators Sit and wait predators Cryptic predators- mantids that look like flowers Others such as robber flies or dragonflies wait in prominent areas Trap-making predators Active foraging Random searching Syrphid larvae casting for prey When one is encountered, feed but otherwise cast further Do you believe this example from your text, after seeing the film of syrphids eating beetle larvae???

Directional searching Based often on multiple cues Stepwise searching approach Used by predators and by parasites (biting flies, etc) Cues Chemical Substances emitted by prey Frass of prey (feces) Sound Luring prey with light Phoresy- predator/parasite rides on another species and is transferred to prey bird lice transported by hippoboscidae bot flies transported by mosquitoes Bio 355 Lecture 19 December 1, 2004 2

Prey manipulation Raptorial legs Elongate spiny legs Prey captured and held by holding spiny segment against another one Mouthpart modifications Piercing and sucking mouthparts Suck fluids from insects Inject toxins and enzyme rich saliva Mandibles Hardened elongate mandibles that pierce cuticles Sucking tube may be formed (e.g. neuropterans) Modified labium-dragonflies

What are parasitoids? Larva of insect develops inside another one It pupates and emerges from the body Sometimes single parasitoids, sometimes many Parasitoids can develop slowly or rapidly in host Entering host Wasps Female lays egg in host Wasp develops inside Sometimes female must lay egg through bark or through a gall Flies Female sometimes lays egg in host Other times she deposits her eggs near them First instar larvae locate host and bore into them They then undergo hypermetamorphosis at the next molt and grow as sessile larvae inside Host use by parasitoids

Often specialize on one or a few hosts

Can discriminate between parasitized and non parasitized hosts

Host marking by previous parasitoid Superparasitism can occur under certain circumstances

Rare hosts, related to parasite number

High fecundity parasites with small eggs

Multiparasitism- host receives eggs of more than one parasitoid species Bio 355 Lecture 19 December 1, 2004 3

Hyperparasitism-

parasitoids of the parasitoid of the host found among wasps, bombyliid flies, and conopid flies

Insects as endoparasites of other insects: order Stresiptera

Few hundred exclusively parasitic species

Feed mostly on hemiptera and hymenoptera

Can switch hosts

Can sterilize hosts

Insect defenses against predation/parasitism (Ch. 13, pp 333-340)

Defense by hiding? Camouflage Treehoppers Moths on leaves Katydids Countershading Industrial melanism

Startle display Eyespots on wings Flashes of color when moths take flight Bio 355 Lecture 19 December 1, 2004 4

Chemical defense Class 1- irritate, hurt or poison Action of substances Immediately acting substances Delayed acting substances Alkaloids, cyanides, cardenolides Effective against vertebrates Often aposematic (monarch, some chrysomelids, bright moths) Class 2- antifeedant Antifeedant chemicals that simply smell or taste bad Ketones, aldehydes, acids, terpenes Stink bugs, some termites, beetles May work better against insects (e.g. ants) and not so well against birds Compounds often work together

Parasitoid encapsulation (back to Chapter 12)

Blood cells surround parasitoid Form a capsule that encloses and kills intruder How do parasites counter this? Avoidance Life stages (e.g. eggs) Tissues (e.g. ganglion or salivary gland Evasion Cloaking itself in a membrane of host tissue so it's not recognized Rapid development in host Destruction of host immune system Suppression of host response with viruses Subversion Parasitoid development despite host response Parasite can live in encapsulated mass feeding rapidly from one opening