Critical Reasoning

Insects can see ultraviolet light and are known to identify important food sources and mating sites by sensing the characteristic patterns of ultraviolet light that these things reflect. Insects are also attracted to Glomosus spiderwebs, which reflect ultraviolet light. Thus, insects are probably attracted to these webs because of the specific patterns of ultraviolet light that these webs reflect.
Which one of the following, if true, most strongly supports the argument?

(A) When webs of many different species of spider were illuminated with a uniform source of white light containing an ultraviolet component, many of these webs did not reflect the ultraviolet light.
(B) When the silks of spiders that spin silk only for lining burrows and covering eggs were illuminated with white light containing an ultraviolet component, the silks of these spiders reflected ultraviolet light.
(C) When webs of the comparatively recently evolved common garden spider were illuminated with white light containing an ultraviolet component only certain portions of these webs reflected ultraviolet light.
(D) When Drosophila fruit flies were placed before a Glomosus web and a synthetic web of similar pattern that also reflected ultraviolet light and both webs were illuminated with white light containing an ultraviolet component, many of
the fruit flies flew to the Glomosus web.
(E) When Drosophila fruit flies were placed before two Glomosus webs, one illuminated with white light containing an ultraviolet component and one illuminated with white light without an ultraviolet component, the majority flew to the ultraviolet reflecting web.


This is from an LSAT, OA: E

Why is it not D? If I understood the passage correctly it's not necessarily the UV component of the web that attracts the flies, but the specific pattern reflected by that web. That is exactly what D states. Two webs illuminated with UV. One has a patter, one doesn't. Flies pick the one with the pattern.

E on the other hand states two webs, one illuminated with UV, one without. Flies flew to the one with UV. Doesn't really support the conclusion.

The conclusion is that they fly to webs becuase of the UV patterns so E does support becuase if they have two webs to choose from and they choose the UV one then it is more likely they are attracted to the UV rather than something else about the web.

D doesn't support becuase both webs has UV but the fly chose the one web anyway, that means that the fly isn't really attracted to the UV because if that were true they would have gone to both equally.

Becky thanks for replying, but isn't the conclusion of the stimulus that they are attracted to specific patterns of UV, rather than simply UV. Or did I misread it? This line is what I thought was the conclusion:

Thus, insects are probably attracted to these webs because of the specific patterns of ultraviolet light that these webs reflect.

Becky thanks for replying, but isn't the conclusion of the stimulus that they are attracted to specific patterns of UV, rather than simply UV. Or did I misread it? This line is what I thought was the conclusion:

Thus, insects are probably attracted to these webs because of the specific patterns of ultraviolet light that these webs reflect.

Same confusion with me too.
Can someone throw light on why the "Specific Pattern" of the UV light is not considered the main conclusion?

yes, the conclusion is that they are attracted to the patterns created by the UV light - thus E works because when you put two of the same webs in front of the flies but one is in white light and one is in UV light (showing the pattern) most of the flies flew to the UV web, which means they are in fact attracted to the UV patterns, becuase they can only be seen under UV light. The patterns would be uniform across the Glomulus webs - becuase the argument says that the flies are attracted to the patterns these webs show under UV light thus the patterns are only visible under UV light. In D they put up two webs that show similar patterns under UV light and the flies chose the Glomosus web which means they are probably attracted by something else. The words "similar patterns" are there to show that the webs would refelct similar patterns of light. In E they do an experiment with the proposed cause and without the proposed cause and get the expected result, thus strengthening the argument.