It does look like a flatid bug---so Order Hemiptera, Family Flatidae---so far.

Have you caught this insect yet? Are there others like it on your lemon? This insect may just sit there while you sneak up on it. And it may jump and take flight, too. If you can see more of these bugs on the tree, you have a better chance of catching at least one of them.

Do you have---or can you borrow an insect sweep net? Lemons have spines which can interfere with net use, however. Another idea.....do you have a white or light-colored dish pan? Sneak up on the insect, position the pan just under it and whack the branch the insect is on. If/when it falls into the pan, clap a small empty food container (cottage cheese cup?) over it. Take the pan indoors where it's likely cooler and there's a place to set down the pan. Slide a stiff piece of paper or light cardboard under the food container where the bug is, then turn over the food container using the cardboard as the 'lid.'

So now what? If you want it alive, you'll have to make some fresh cuttings of your citrus twigs, put them into a jar of water inside a 'cage' of some sort, releasing your live insects inside the cage. Jumping, flying insects may not be so easily caged or cared for. Keeping insect colonies alive takes a lot of work, and it may not work.

If you need the insect(s) for students to ID, once you catch it (or them) put them into your freezer. An overnight stay will kill them. If you don't need the insects right away, they could stay in the freezer longer---BUT---when they come out, if they are still reasonably pliable, you'll need to pin them with insect pins right away. If they are dry and stiff, you'll need to relax the specimens.

Find the lid for your cottage cheese cup. Tear off about 1/4 sheet of paper towel and moisten it with water (not soppy wet, though). Put that in the bottom of your cup. Turn the cup on its side, put the bugs inside and put on the lid, propping the cup so it won't roll off the counter.

An insect pin, size 1 or 2 would probably be about the right size. SEWING PINS OR QUILTING PINS WON'T WORK---TOO THICK, TOO SHORT AND THEY WILL RUST QUICKLY. Pin through the thorax and put it into your collection box for the students. They should be able to see the features needed for ID through their dissecting scopes. The less you handle the insect, the less white wax dust will wear off it.

If the students won't be looking at the specimens anytime soon, keep the specimen in the freezer until you need it. PR will have oodles of little pests ready to eat dead insects.  

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I have looked at 3 possible IDs for this insect. Since you can see details from the real insect better than I can see them in this photo---is the genus and species critical for students to determine? Or just take it to Family and call it good?
Here's the 3 IDs I found....there might be more...... 

Ormenoides venusta is supposed to have a faint orange tinge to the wing margins---according to Dr. Andrew Hamilton, an authority on this and related families. I imagine the color of the wing edges and eyes fades after death, however.

Flatormenis proxima is supposed to have a more angular edge on the forewing than Ormenoides. No faint orange on the wing edge either.

Metcalfa pruinosa also has the body and wings dusted with white waxy material, but note the 2 (sometimes more) tiny dark dots near the base of the forewings. This one is found on citrus as well as a variety of other trees and shrubs. It occurs as far west as New Mexico and I know it occurs on honeysuckle vines.

As you can see, I pulled some photos from bugguide. All 3 spp. occur in the eastern US and into SE Canada---where the collectors who contribute to bugguide live. PR is a little outside the usual area where insects are submitted commonly for ID---but I would keep all 3 as possibilities to compare with your specimens. Of course, the students can do that, too, if needed.

I hope this helps.......

  

Thank you Dr. Carol Sutherland!!!
By the looks on the pictures, I think is a Flatormenis proxima. By the way I collected in eppie tubes. Let me know if you want me to send one or two or as many as you need. 
Thank you again

I would be delighted to receive specimens (plural) if they aren't that difficult for you to catch. Ideally, I would like them 'dry'. They can be placed in a small box (little jewelry box?) padded with a wadded/crinkled Kleenex and covered with another crinkled Kleenex. Then put the whole thing into a larger box** with a bit of padding (crumple a sheet of newspaper?) inside to keep the Post Office from crushing, squashing or otherwise shaking them to pieces.

**Do your Post Offices in Puerto Rico have those handy Priority Mail/Flat Rate boxes that you assemble yourself? If so, the 'small' box would likely work fine here. Take all of your goodies to the Post Office with my address (below), get the box, follow the simple assembly directions, insert the goodies, seal and have them apply the postage. It works.[

Before sealing the box, could you write your name, city and date of collection on a slip of paper? We will use this to make specimen labels.

What I'll do with the specimens here is 'relax them' (add moisture) so they can be pinned or glued onto paper points. Labels are applied on each pin and the identified material goes into our NMSU Arthropod Collection where it will be kept (in good shape, too) forever. We have some specimens over 100 years old---done the same way. We use the collection for research, teaching and Extension work (I do the latter) as well as outreach to children and adults statewide. Add 4H and Future Farmers of America and that's our basic audience.

Yes, I would like to receive specimens---so please send them to:

Dr. Carol Sutherland
Extension Plant Science Department
Box 30003 MSC 3AE
New Mexico State University
Las Cruces, NM 88003-8003

Thanks so much.............