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GUIDE TO INSECT FAMILIES, WITH EMPHASIS ON

PARASITOIDS & PREDATORS ^{1 2}

E. F. Legner, University of California, Riverside

(Email Contacts)

This key is in a form commonly used in North America. If the statement is true, proceed

to the designated couplet, whereas if it is false, go to the "b" portion of the couplet. Numbers

in parentheses refer to the previous couplet or couplets read. Details on families may be found

in <taxnames.htm>. See MORPHOLOGY to learn about insect structure. [For less powerful

connections, please try <insect1.htm> ]

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----Please CLICK on desired underlined categories to view pictures and to navigate in the key

[A will display all pictures for both pairs of a couplet]

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1a. Adults have well-developed wings................................................................................…................….......2

1b. Adults wingless or with wings vestigial or rudimentary (nymphs, larvae & some adults)….......….28

2a (1a). Wings membranous, not hardened or leathery..........................................................…….............….3

2b. Front wings hardened or leathery, at least at base (Figs.A-E); hind wings, if present, usually

membranous..... A….................................................................................................................................24

3a (3a). Only 1 pair of wings...............................................................................................................……..........4

3b. Two pairs of wings......................................................................................................................…....….....10

4a (3a). Body shaped like a grasshopper; pronotum ( = dorsal plate or sclerite of prothorax)

extends back over abdomen and is pointed apically; hind legs enlarged (Figs.A-F)

…………………………………………………......……. [pygmy grasshoppers... A......Orthoptera

4b. Body not shaped like a grasshopper; pronotum not as previous; hind legs not so enlarged

..................................................................................................................................…......................….....5

5a (4b). Antennae with at least 1 segment bearing along lateral process; front wings minute,

hind wings like a fan (Figs.A-B); minute insects [male twisted-winged parasitoids) A

………………………………………………………………........…........................Strepsiptera..…..217

5b. Does not fit previous description exactly.................................................................................…....…..... 6

6a (5b). Abdomen with 1-3 thread-like or bristle-like caudal (= tail) filaments; mouthparts vestigia........7

6b. Abdomen without thread-like or bristle-like caudal filaments; mouthparts almost always

developed, mandibulate (= chewing) or for sucking....………............................................….......…....8

7a (6a). Antennae long and conspicuous; abdomen terminates in one long style (rarely 2); wings

with a single forked vein (Fig.A); halteres (= knobbed modified hind wings) present

and usually terminating in a hooklike bristle; minute insects, usually <5 mm in length

[male scale insects] ........ A.......................................................................................…......Homoptera

7b. Antennae short, bristle-like, and inconspicuous; abdomen with 2-3 thread-like caudal

filaments; wings with numerous veins and cells; halteres absent; usually >5 mm in length

(Fig. A) [mayflies]...........................................................................................................Ephemeroptera

8a (6b). Tarsi almost always with 5 segments; mouthparts for sucking; hind wings knob-like, reduced to

halteres (Figs.A-E); body lightly sclerotized (= hardened) [flies]..... A..........Diptera...........88

8b. Tarsi with 2-3-segments; mouthparts variable; hind wings reduced or absent, not haltere-

like.........................................................................................................……..............................................9

9a (8b). Mouthparts mandibulate (Figs.A-E)[psocids]...... A...................................................Psocoptera

9b. Mouthparts for sucking (Figs.A-C) [some planthoppers & leafhoppers]............................Homoptera

10a (3b). Wings mostly or entirely covered with scales (Fig. A); mouthparts usually in the

form of a coiled proboscis (Fig.B); antennae with many segments (Figs.C-G)

[butterflies & moths] ... A................................................................................Lepidoptera….....227

10b. Wings not covered with scales; mouthparts not a coiled proboscis, antennae variable…….........11

11a (10b). Wings long and narrow, veinless or with only 1-2 veins, and fringed with long hairs

(Fig.A); tarsi with 1-2 segments, the last segment swollen; minute insects, usually <5 mm

in length (Figs.A-D) [thrips]....... A...........................................................................Thysanoptera

11b. Wings not as previously described , or if wings are somewhat linear, then the tarsi have more than 2

segments.…………...................................................................................................................…….......12

12a (11b). Front wings relatively large and usually triangular; hind wings small and usually

rounded, the wings at rest held together above the body; wings usually with many veins

and cells; antennae short, bristle-like, and inconspicuous; abdomen with 2-3 thread-like

caudal filaments (Fig.A); delicate, soft-bodied insects (Fig.B) [mayflies]... A..Ephemeroptera

12b. Not as previously described......................................................................................…..….......................13

13a (12b). Tarsi with 5 segments......................................................................................…..................….........14

13b. Tarsi with 4 or less segments....................................................................................................……..........17

14a (13a). Front wings obviously hairy; mouthparts usually very much reduced except for the

palps; antennae usually as long as body or longer; somewhat soft-bodied insects

(Figs.A-F) [caddis flies.... A...................................................................….......................Trichoptera

14b. Front wings not hairy, at the most with microscopic hairs; mandibles well developed;

antennae shorter than body....................................................................................................…...........15

15a (14b). Body quite hard, wasplike insects; clypeus not elongated; the abdomen often

constricted at base, 1st abdominal segment fused to thorax; fore wings distinctly larger

than hind wings and with fewer veins; front wings with 20 or less cells (Figs.A-F)

[sawflies, bees and wasps]....... A................................................................Hymenoptera……...118

15b. Body soft, not wasplike, the abdomen not constricted at base; hind wings about the same

size as front wings and usually with about as many veins; front wings frequently with more

than 20 cells.................................................................................................................................…..........16

16a (15b). Costal area of front wings (= area just behind anterior margin) nearly always with

numerous cross veins per pair of longitudinal veins (Fig.A), or if not (Fig.B) then hind wings shorter

than front wings; mouthparts not prolonged ventrally into a beak

(Figs.C-G) [lacewings, dobsonflies, antlions] ... A.......................................Neuroptera……..194

16b. Costal area of front wings with not more than 2-3 cross veins per pair of longitudinal veins (Fig.A);

mouthparts prolonged ventrally to form a beak-like process (Figs.B-D)

[scorpionflies]....................................................................................................................….....Mecoptera

17a (13b). Hind wings as long as front wings and of the same shape or wider at base, the wings

at rest held above the body or extended out (never held flat over abdomen); wings with

many veins and cells; antennae short, bristle-like, and inconspicuous; abdomen long and

slender (Figs.A-B); tarsi with 3 segments; length 20-85 mm [dragonflies, damselflies) A

...............................................................................................................…….......................……...Odonata

17b. Not as previously described.................................................................................................…….............18

18a (17b). Mouthparts for sucking.................................................................................……...........................19

18b. Mouthparts mandibulate (= chewing).....................................................................…...............…..........20

19a (18a). Beak arises from front part of head (Figs.A-E) [gnat bugs..Hemiptera /Heteroptera...A..140

19b. Beak arises from hind part of head (Fig.A) [cicadas, some hoppers, aphids, some

psyllids and whiteflies].........................................................................…..............................Homoptera

20a (18b). Tarsi with 4 segments; front and hind wings similar in size, shape and venation

(Figs.A-E) cerci tiny or absent [termites]..... A........…………............................................…..........Isoptera

20b. Tarsi with 3 or less segments; hind wings usually shorter than front wings; cerci either

present or absent.....................................................................................................................……............21

21a (20b). Hind wings with anal area nearly always enlarged and forming a lobe, which is folded

like a fan at rest; venation varying from normal to very dense, the front wings usually with

several cross veins between Cu-1 and M and between Cu-1 and Cu-2 (Fig. A); cerci

present and often fairly long; mostly 10 mm or more in length; nymphs aquatic, and adults

usually near water (Figs.A-F) [stoneflies].... A.............................................................Plecoptera

21b. Hind wings without an enlarged anal area and not folded at rest; venation normal or

reduced, with no extra cross veins; short cerci present or absent; mostly 10 mm in length

or less; nymphs not aquatic and adults not regularly near water.........................................….......22

22a (21b). Tarsi with 3 segments, basal segment of front tarsi enlarged A

……………………………………………................………… (Figs.A-B) [webspinners].Embioptera