When an invading insect threatens an ant colony’s territory or food so

TheGraceful

In official questions, you will not find an option subjectively "superior" to another. There will always be only one correct answer.

When an insect threatens an ant colony’s territory or food sources, ants will attack it.
This deters even aggressive flying insects, such as wasps.
Ants do not attack all insects within their territory, however.
For example, riodinid caterpillars commonly live harmoniously among South American ants.
These caterpillars, which are a favorite prey of wasps, produce secretions the ants consume as food.

We need a conclusion/inference. This means there should be no new information in the correct option.

(A) The secretions produced by riodinid caterpillars are chemically identical to substances secreted by plants on which South American ants also feed.

Plants on which ans feed is new info.

(B) South American ants are more likely to be successful in defending their food sources and territory against intruders than are ants that live elsewhere.

Ants elsewhere - new info

(C) With the sole exception of riodinid caterpillars, South American ants will vigorously attack any organism other than ants that use riodinids as a source of food.

Not implied. We do not know anything about "all other organisms that use riodinid caterpillars as food". There may be another insect X that uses riodinid caterpillars' secretions as food but lives harmoniously with ants because of some other benefit it provides to the ants.

(D) Among insect species that inhabit South America, wasps are the only kinds of organism other than ants that use riodinid caterpillars as a source of food.

Not given.

(E) Riodinid caterpillars in South America that live among ants are less likely to be attacked by wasps than those that do not live among ants.

Correct. We know that the wasps are deterred by ants. If riodinid caterpillars are in ants' territory, it is likely that wasps will not enter the territory.

Answer (E)

Thank you VeritasKarishma,
Your explanation about answer choices made sense to me. More thanks for clarifying difference between GMAT official and LSAT official questions - it relived another bigger stress.

This is clearly an inference Question as there is no conclusion or claim in the passage.
fact 1) Native ants attack intruders except the R caterpillar, which lives peacefully with these native aunts
fact 2) This kind of attack also discourages the wasps, they stay away.]
fact 3) wasps eat R Caterpillar
Thus, if there are more wasps around then there will be less Rcaterpillar who live with aunts. If less wasps are around, then more R caterpillar will be able to live peacefully with aunts.

A) The secretions produced by riodinid caterpillars are chemically identical to substances secreted by plants on which South American ants also feed. = Plants? we dont know if they feed on plants and this isnt relevant. OUT

(B) South American ants are more likely to be successful in defending their food sources and territory against intruders than are ants that live elsewhere. = Elsewhere? How do we know? OUT

(C) With the sole exception of riodinid caterpillars, South American ants will vigorously attack any organism other than ants that use riodinids as a source of food. = ANY Other Organism? how do we know if these ants attack other organisms or not, as it is not given in passage. It only talks about ant intruders. oUT

(D) Among insect species that inhabit South America, wasps are the only kinds of organism other than ants that use riodinid caterpillars as a source of food. = we dont know if these are the ONLY kind of Organisms. OUT

(E) Riodinid caterpillars in South America that live among ants are less likely to be attacked by wasps than those that do not live among ants. = Exactly! R Caterpillar between Ants = native ants will protect RC because of the attack mechanism and thus wasps will stay away. elsewhere, RC will more likely be attacked.

Riodinid caterpillars in South America that live among ants are less likely to be attacked by wasps than those that do not live among ants.

I am a little confused about this choice. I understand that if wasps attack the caterpillars, the ants will protect the caterpillars. But that doesn't mean they are less likely to be attacked. The attack is very likely, but then how successful will the attack be is the next question.

Assumption: If wasps are smart then they learn a lesson and don't attack. Without this assumption, i don't know how this choice is correct.

Don't forget the second sentence. The text tells us that the ant attacks "can successfully deter" wasps. That means that in at least some cases, the wasps are kept away. Therefore, wasp attacks on the caterpillars are less likely than they would otherwise be.