How does such methodical & precise predatory behavior evolve in tiny insect?

[astro]

The behavior of this waspis fascinating and involves what amounts to complex, multi-step predation behavior on cockroaches. All this has to be wired into a “ganglion/brain” structure no bigger than the head of a pin. As a general question how would such precise and complex (seemingly almost knowingly intelligent) multi-step behavior like this develop as function of evolution?

Find roach
sting for limb paralysis
locate precise ganglia center - sting again
chew off half of antenna and “steer” to burrow
lay egg on roach
cover burrow

As early as the 1940s it was reported that female wasps of this species sting a cockroach (specifically a Periplaneta americana, Periplaneta australasiae or Nauphoeta rhombifolia)[1] twice, delivering venom. A 2003 study[2] using radioactive labeling demonstrated that the wasp stings precisely into specific ganglia of the roach. It delivers an initial sting to a thoracic ganglion and injects venom to mildly and reversibly paralyze the front legs of its victim. The biochemical basis of this transient paralysis is discussed in a 2006 paper.[3] Temporary loss of mobility in the roach facilitates the second venomous sting at a precise spot in the victims’s head ganglia (brain), in the section that controls the escape reflex. As a result of this sting, the roach will first groom extensively, and then become sluggish and fail to show normal escape responses.[4] In 2007 it was reported that the venom of the wasp blocks receptors for the neurotransmitter octopamine.[5]

The wasp proceeds to chew off half of each of the roach’s antennae.[1] Researchers believe that the wasp chews off the antenna to replenish fluids or possibly to regulate the amount of venom because too much could kill and too little would let the victim recover before the larva has grown. The wasp, which is too small to carry the roach, then leads the victim to the wasp’s burrow, by pulling one of the roach’s antennae in a manner similar to a leash. Once they reach the burrow, the wasp lays a white egg, about 2 mm long, on the roach’s abdomen. It then exits and proceeds to fill in the burrow entrance with pebbles, more to keep other predators out than to keep the roach in.

With its escape reflex disabled, the stung roach will simply rest in the burrow as the wasp’s egg hatches after about three days. The hatched larva lives and feeds for 4–5 days on the roach, then chews its way into its abdomen and proceeds to live as an endoparasitoid. Over a period of eight days, the wasp larva consumes the roach’s internal organs in an order which maximizes the likelihood that the roach will stay alive, at least until the larva enters the pupal stage and forms a cocoon inside the roach’s body. Eventually the fully grown wasp emerges from the roach’s body to begin its adult life. Development is faster in the warm season

.

[CalMeacham]

You think that’s impressive? How about complex behavior where there’s even less of a brain involved?

There’s the parasitic flatworm that causes the host snail’s eyestalks to take on the color, banding, and movement behavior of a caterpillar, thereby guaranteeing that it will be eaten by a bird (which then spreads the flatworm’s young):

Leucochloridium Paradoxum, common name green-banded broodsac, is a parasitic flatworm (or “helminth”) that uses gastropods as an intermediate host.

The worm in its larval, miracidia stage, travels into the digestive system of a snail to develop into the next stage, sporocyst. The sporocyst grows into long tubes to form swollen “broodsacs” filled with tens to hundreds of cercariae. These broodsacs invade the snail’s tentacles (preferring the left, when available), causing a brilliant transformation of the tentacles into a swollen, pulsating, colorful display that mimics the appearance of a caterpillar or grub. The broodsacs seem to pulsate in response to light intensity, and in total darkness do not pulse at all. The infection of the tentacles of the eyes seems to inhibit the perception of light intensity. Whereas uninfected snails seek dark areas to prevent predation, infected snails have a deficit in light detection, and are more likely to become exposed to predators, such as birds. Birds are the definitive hosts where the cercariae develop into adult distomes in the digestive system of the bird. These adult forms sexually reproduce and lay eggs that are released from the host via the bird’s excretory system. These droppings are then consumed by snails to complete the life cycle of this parasitic worm.

The resulting behavior of the flatworm is a case of aggressive mimicry, where the parasite vaguely resembles the food of the host. This gains the parasite entry into the host’s body; this is unlike most other cases of aggressive mimicry, in which only a part of the host resembles the target’s prey and the mimic itself then eats the duped animal.

Cordyceps & Leucochloridium Paradoxum

https://search.yahoo.com/search;_ylt=A0LEV1z_iWxVuhgAQzdXNyoA;_ylc=X1MDMjc2NjY3OQRfcgMyBGZyA3lmcC10LTI1MgRncHJpZANjbzlQSE9zdFFfYWt3MkR5TWRXX2lBBG5fcnNsdAMwBG5fc3VnZwM0BG9yaWdpbgNzZWFyY2gueWFob28uY29tBHBvcwMwBHBxc3RyAwRwcXN0cmwDBHFzdHJsAzMwBHF1ZXJ5A2Z1bmd1cyBzbmFpbCBjYXRlcnBpbGxhciBtaW1pYwR0X3N0bXADMTQzMzE3NjU5Mg--?p=fungus+snail+caterpillar+mimic&fr2=sb-top-search&fr=yfp-t-252&fp=1
Or the liver fluke that causes complex changes in an ant’s hevaior so that it gets eaten by sheep?

Dicrocoelium dendriticum spends its adult life inside the liver of its host. After mating, the eggs are excreted in the feces.

The first intermediate host, the terrestrial snail (Cochlicopa lubrica in the United States), consumes the feces, and becomes infected by the larval parasites. The larvae (or miracidium) drill through the wall of the gut and settle in its digestive tract, where they develop into a juvenile stage. The snail attempts to defend itself by walling the parasites off in cysts, which it then excretes and leaves behind in the grass or substrate.

The second intermediate host, an ant (Formica fusca in the United States[11]), uses the trail of snail slime as a source of moisture. The ant then swallows a cyst loaded with hundreds of juvenile lancet flukes. The parasites enter the gut and then drift through its body. Most of the cercariae encyst in the haemocoel of the ant and mature into metacercariae, but one moves to the sub-esophageal ganglion (a cluster of nerve cells underneath the esophagus). There, the fluke takes control of the ant’s actions by manipulating these nerves.[12] As evening approaches and the air cools, the infected ant is drawn away from other members of the colony and upward to the top of a blade of grass. Once there, it clamps its mandibles onto the top of the blade and stays there until dawn. Afterward, it goes back to its normal activity at the ant colony. If the host ant were to be subjected to the heat of the direct sun, it would die along with the parasite. Night after night, the ant goes back to the top of a blade of grass until a grazing animal comes along and eats the blade, ingesting the ant along with it, thus putting lancet flukes back inside their host. They live out their adult lives inside the animal, reproducing so that the cycle begins again.[13][unreliable source?][14][unreliable source?][15] Infected ants may contain 100 metacercariae, and a high percentage of ants may be infected. Typical infections in cattle may be in the tens of thousands of adult worms.[16]

Dicrocoelium dendriticum

There are other complex behavior-altering capabilities exhibited by parasitic fungi, which don’t have brains at all.
I look at it as a pretty long road of evolutionarily shaped changes. The wasps, parasitic worms, and fungi don’t think any of this out – they’re simply the most successful of a series of random changes that, pared by the statistics of survival, effectively programmed in every link of this complex behavior.

[astro]

Thanks for fascinating example!

[dracoi]

I think the the first thing to recognize is the massive varieties of behaviors that are out there. For example, I’m always reminded of a story about a poor Peregrine falcon that failed to mate because he insisted on offering the females a dead mouse when they wanted a dead bird. Even in a population with an established behavior, there are still a lot of individual outliers contained in a few fringe percentage points.

An example from my personal experience with gold fish: In every batch of 100 gold fish, 98 of them school like normal, but there’s 2 who want to be off doing their own thing. 90 of them will eat flakes or pellets, but there are 5 who will only eat pellets and 5 who will only eat flakes. In the wild, these outliers would probably die off or fail to reproduce.

If it so happens that a one in a million outlier reproduces more successfully than their peers, it won’t take long for that to become the standard behavior throughout the population, especially when many species have offspring in the thousands each generation. It’s not like humans where your two kids lead to four grand kids… it’s a case where their thousand kids lead to a million grand kids and a billion great grand kids. It might take longer to spread that mutation geographically than for it to dominate the genes in a particular local population. As long as conditions remain the same, that particular behavior dominates the population. The behavior remains the standard until some outlier does better or until an external change to the environment favors something else.