Because the tube has no additional glass to interfere with the image that arrives at the sensor it will be sharper, and because it holds the lens further from the sensor it magnifies the subject hugely.

Example with a Pentax A 50mm f1.7, however you have to get very close. To successfully shoot damsells and dragons you will need to be further from your subject for two reasons. 1. they are twitchy and 2 they tend to be quite large and so to get them all in the picture you need to be some distance away.

Tubes and an old 50mm is pretty much the cheapest option you will get. However dragonflies tend to be a bit more difficult to get close to so popping an old manual 300mm on a 31mm tube will give you a higher magnification. Your best weapon is stealth though.
There's a whack of good gear here if you want to get into macro.

I was going to say make sure you have WR for the same reasons as above

The horizon needs straightening too

That's the same single contact that I have on my 50mm f1.7 so no reason why it shouldn't work. I've just tested the combo on my 5iis and it's fine. Looks like a good clean of the contacts is in order.

Some more from this weekend...

1. Rooster tails



2. Tail wagging



3. Panning



4. Backlit spray

Another from this weekend's Celtic Challenge. I am still not sure whether Pentax is any good for fast action sport ..... I have another 800+ of these if you want further evidence of Pentax shortcomings
K-5iis coupled with DA* 50-135 - TAV 1/1000 F5.6 ISO 400 ... zero PP sharpening, shot as JPEG

The button layout is identical and the menu options are very similar with a few additions on the ii (Why oh why did you not go for the iis!) I went from the 7 to the iis and the difference is astronomical, it's like going from 1970's telly pictures to HD in one jump.

I always put in the long end, my reasoning is the camera needs to approximate the physical size of the lens. Surely it is this parameter that makes the difference when stabilising the lens, the longer the lens the more the element end will move around due to breathing or heartbeat. A 200mm lens will require more adjustment than a 50mm lens will it not? So if you have a manual 50-200 it will be just as twitchy at 50mm as it is at 200mm due to its physical size. I for one would guard against this by putting in the long end measurement.