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Overview of Orders of Insects

Probably many first time visitors to Bugguide would benefit from an overview of all the orders of insects with some explanation of their main identifying characteristics. This is not a technical key but rather a series of tips for a “spot” identification of orders. It follows the one created by Arnett ((1), pages 63-68) for beginners.

Insects with:

1. Four large wings, covered by scales:
Order Lepidoptera - Butterflies and Moths


2. Four wings; the first pair thickened or hardened.
       a) First pair of wings usually as long as abdomen protecting second pair of wings that are membranous. Abdomen without forceps:
Order Coleoptera – Beetles


       b) First pair of wings reduced in size, hind wings are large:
Order Strepsiptera - Twisted-winged Insects


3. Similar to Coleoptera but with short wing covers and with abdominal forceps:
Order Dermaptera - Earwigs


Caution: If there are no forceps, it is probably a beetle, Family: Staphylinidae


4. Resembling Coleoptera, but the posterior half of the front wings somewhat translucent or thinner and with veins. They have sucking mouth parts:
Order Hemiptera (Suborder Heteroptera) - True Bugs



5. Four wings, front ones somewhat thickened.
       a) Jumping hind legs. Hind wings, when open, spread like fans:
Order Orthoptera - Grasshoppers, Crickets, Katydids


       b) Wings similar to Orthoptera but they have grasping front legs instead of jumping hind legs:
Order Mantodea - Mantids


       c) Similar to Orthoptera but with flattened body, long antennae and no enlarged legs:
Order Blattodea - Cockroaches and Termites


       d) Similar to Orthoptera but long, stick-like body and no enlarged legs:
Order Phasmatodea – Walkingsticks


6. Two pairs of membranous wings similar in size and texture.
       a) Wings held horizontally. They can’t be folded:
Order Odonata (Suborder Anisoptera) - Dragonflies


       b) Wings held folded vertically above abdomen:
Order Odonata (Suborder Zygoptera) - Damselflies


7. Four membranous wings, front wings larger than hind ones.
       a) Abdomen with two or three long filaments:
Order Ephemeroptera – Mayflies


       b) Similar to Ephemeroptera but wings are held over the abdomen. No abdominal filaments:
Order Neuroptera - Antlions, Lacewings and Allies


       c) Similar to Neuroptera but with two or three abdominal short filaments:
Order Plecoptera - Stoneflies


       d) Wings held rooflike over abdomen. Large head. Sucking, piercing mouth parts:
Order Hemiptera (Suborders Auchenorrhyncha and Sternorrhyncha)- Cicadas, Hoppers, Aphids and Allies


       e) Hind wings smaller than front wings with few cross veins. Mouth parts not piercing; head joined loosely to thorax:
Order Hymenoptera - Ants, Bees, Wasps and Sawflies


       f) Head shaped as a beak, with chewing mouth parts:
Order Mecoptera - Scorpionflies, Hangingflies and Allies


8. Wings not like those of any of the previous orders:
       a) Wings with setae or fringes, sucking mouth parts, usually very small. Some specimens wingless:
Order Thysanoptera – Thrips


       b) Front and hind wings similar, with few veins; many specimens wingless; chewing mouthparts; 3-10 mm. long:
Epifamily Termitoidae (formerly Order Isopoda) - Termites


       c) Under 3 mm. (See illustration):
Order Zoraptera - Zorapterans


       d) Under 5mm. (See illustration):
Order Psocodea - Barklice and Booklice


       e) Under 7 mm. (See illustration):
Order Embiidina – Webspinners


       f) Wings covered with hairlike setae; long antennae:
Order Trichoptera - Caddisflies


9. Only one pair of wings; membranous, with conspicuous veins. No abdominal filaments:
Order Diptera – Flies



10. No wings, usually with scales and long abdominal filaments.
(Note: some members of other orders are also wingless but body shape resembles that of winged members of the same order, e.g. ants, bedbugs, termites, etc.)

       a) Body cylindrical. Tip of abdomen with one long filament and two shorter ones:
Order Microcoryphia - Bristletails


       b) Body flattened. Lateral filaments at tip of abdomen usually as long as middle one:
Order Zygentoma - Silverfish


       c) Body cylindrical. Long antennae 28-50 segments
Order Notoptera – Rock crawlers


11. No wings, ectoparasites

       a) Laterally flattened, hind legs adapted to jumping:
Order Siphonaptera - Fleas


       b) Flattened top to bottom; chewing mouthparts; parasites of birds and some mammals:
Order Mallophaga - Chewing Lice


       c) Flattened; sucking mouthparts; ectoparasites of mammals:
Order Anoplura - Sucking Lice



(1)Arnett, Ross H. American Insects. Pages: 63-68


......................................................................

I will be very grateful for any suggestions, corrections, comments, etc. I have never been very good with keys and I am very ignorant about entire orders of insects; so I am sure that many of you have some good ideas that could help me improve this article.

Old Link
The link under Order Dictyoptera - Mantids does not seem to point to anything useful.

 
Thanks
I am glad you caught that. The taxonomy was changed a year after I wrote this article. This led me to finding three other problems. I wish I had known this sooner. I hope that there are no more changes at the higher taxonomic levels.

Very nice
Since this thread popped up...under Plecoptera, only two abdominal filaments (cerci) will be present. Mayflies can have a median filament, but stoneflies won't.

Hi Beatriz,
Since you mention under Orthoptera that the hind wings spread like fans when opened, how about adding this image ;)


Nice Work
Do you want to add a comment about spreadwing damselflies and/or add an image of a "typical" damselfly?

Do you want to add a caution, like your staphylinidae caution, to the fly section mentioning many mimics?

Great overview
Beatriz: Really enjoying this overview, and will eventually read all your articles listed in your Bio on BugGuide. Thanks, Roy

Megaloptera
The article shows Megaloptera in the Neuroptera area. Is there a reason for this that I do not see?

 
Good catch
One image is out of place and Megaloptera is missing. The article followed Arnett's key closely. The order Megaloptera was added to Bugguide after I did this article, and that changes things. After that taxonomic change the key should be completed by adding Megaloptera to it. Work, work, work, sigh!
Thanks, I will look into it.

The representative thumbnail images
within each taxon are most helpful, and similar to what now appear on the Hymenoptera, Coleoptera, and various other Info pages. Wouldn't this be more accessible on the Insects page?

A page of thumbnails -- like a museum drawer full of prepared specimens -- allows people to "let their eyeballs do the walking through the insect pages". To a casual observer (such as my niece, who once described a weevil as "has no wings, just a hard shell with a crack down the middle") Arnett's text may be confusing. His descriptions seem suitable for folks who are comfortable with handling specimens, but that rules out people like my niece.

 
Overview on Insecta page
I thought about it but I heard that some people complained about the slowness due to so many images when opening the Coleoptera page. Anyway, I put a link on the Insecta page, so this article is just one click away from it.
What I keep hoping is that the "Overviews" get their own section, which would be more useful than the sections "Browse" or "Images", or even "Info" in some cases. It would be a real guide, especially for beginners as you point out. I mentioned this to our leader and maybe I should do it again. We all know how busy he is.
Articles like this could be done by anybody (as Sam is doing for Cicadellidae), not just editors, and later on incorporated to the overview pages. That would be a great help.

Another

Very nice,
a great addition!

For someone like me.....
...this is great. Great addition to BugGuide for fairly new users. BTW, if you end up adding any example photos... my request would be a Tree Cricket under Orthoptera. :D

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