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                          GUIDE TO INSECT FAMILIES, WITH EMPHASIS ON

 PARASITOIDS & PREDATORS 1

 

                                                                          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 more powerful

     connections, please try <insect2.key.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

 

22b.    Tarsi with 2-3 segments, basal segment of front tarsi not enlarged................................……….........23

 

23a (22b).    Cerci present; tarsi with 2 segments; wing venation reduced (Figs.A-D); moniliform

                  (= bead-like) antennae with 9 segments............. A...........................................................Zoraptera

 

23b.    Cerci absent; tarsi with 2-3 segments; wing venation not much reduced (Figs.A-D);                  antennae not

moniliform, usually long and hairlike, with 13 or more segments

.....................................................................................................................…...........................Psocoptera

 

24a (2b).    Mouthparts for sucking, beak elongated and usually segmented (Figs.A-B)... A ....…......25

 

24b.    Mouthparts mandibulate........................................................................................…................….............26

 

25a (24a).    Beak arises from front of head (Fig.A); basal portion of fore wing usually

thickened and leathery, but membranous at tip, the tips overlapping at rest (Fig.B)   A

[true bugs]..........................................................................................Hemiptera / Heteroptera.…...140

 

25b.    Beak arises from hind part of head, often appearing to begin at base of front legs; front

wings of uniform texture throughout, the tips not, or only slightly, overlapping at rest

[leafhoppers & some psyllids].....................................................................….......................Homoptera

 

26a (24b).    Abdominal cerci like forceps (Fig.A); front wings short, leaving most of

abdomen  exposed; tarsi with 3 segments (Fig.A) [earwigs]...... A........….................Dermaptera

 

26b.    Abdominal cerci not like forceps, or if cerci appear as such, then front wings cover most of

          abdomen; tarsi variable..........................................................................................................………...........27

 

27a (26b).    Front wings entirely leathery and without veins and usually meet in a straight line

                 down middle of back; antennae generally with 11 or fewer segments and have diverse

               shapes (Figs.A-I); hind wings narrow, usually longer than front wings when unfolded, and

               with few veins (Figs.J-O) [beetles].... A............................................................Coleoptera.…....152

 

27b.    Front wings with veins and either held like a roof over abdomen or overlapping over

                 abdomen when at rest; antennae generally with >12 segments; hind wings broad, usually

                 shorter than front wings, and with many veins (Fig.A), usually folded like a fan at rest

               [crickets, grasshoppers, cockroaches and preying mantids].....................…...................Orthoptera

 

28a (1b).    Body usually insect-like, with segmented legs and usually segmented antennae……............29

 

28b.    Body generally worm-like, body regions (except possibly head) not well differentiated, and

           segmented thoracic legs absent; antennae present or absent........................................…......……....74

 

29a (28a).    Front wings present but rudimentary; hind wings absent or represented by halteres;

           tarsi almost always with 5 segments [some flies]........................................................Diptera……......88

 

29b.    Wings entirely absent or with 4 rudimentary wings and no halteres; tarsi variable.........……........30

 

30a (29b).     Antennae absent; length 1.5 mm or less (Fig.A); usually occur in soil or leaf litter.   A

                       ..................................................................................................................................................Protura

 

30b.    Antennae usually present (sometimes small); size and habitat variable............................…….........31

 

31a (30b).    Ectoparasites of birds, mammals, or honey bees and usually found on the host; body

                   somewhat leathery and usually flattened dorsoventrally or laterally..........................................32

 

31b.    Free-living (not ectoparasitic), terrestrial or aquatic................................................................……......36

 

32a (31a).    Tarsi with 5 segments; antennae short and usually concealed in grooves on head;

                   mouthparts for sucking..................................................................................…...............…..............33

 

32b.    Tarsi with fewer than 5 segments; antennae and mouthparts variable.........................……..............34

 

33a (32a).    Body flattened laterally; usually jumping insects, with rather long legs (Fig.A)   A

                   [fleas]...............................................................................................................................Siphonaptera

 

33b.    Body flattened dorsoventrally; not jumping insects, legs usually short (Fig.A) [louse

flies, bat flies & bee lice]............................................................................................…............Diptera

 

 

34a (32b).    Antennae decidedly longer than head; tarsi 3-segmented (Fig.A) [bed bugs and   A

bat bugs]........................................................................................................Hemiptera / Heteroptera

 

34b.    Antennae not longer than head; tarsi with 1 segment...........................................................………....35

 

35a (34b).    Head as wide as or wider than prothorax; mouthparts mandibulate; parasites of birds

                 (with 2 tarsal claws) and mammals (with 1 small tarsal claw) (Figs.A-D)    A

…………………………………………………………................………….[chewing lice] Mallophaga

 

35b.    Head usually more narrow than prothorax; mouthparts haustellate (= for sucking);

           parasites of mammals with 1 large tarsal claw (Figs.A-B) [sucking lice]…………..........…. Anoplura

 

36a (31b).    Mouthparts for sucking, with a conical or elongated beak enclosing stylets...…….......…....37

 

36b.    Mouthparts mandibulate (sometimes hidden in head), not beaklike.......................……....................41

 

37a (36a).    Tarsi with 5 segments; maxillary or labial palps ( = segmented processes) present

                  .............................................................................................................................…..................................38

 

37b.    Tarsi with 4 or fewer segments; palps small or absent........................................................……..........39

 

38a (37a).    Body covered with scales; beak usually in the form of a coiled tube; antennae long

                   and with many segments [wingless moths]......................................................Lepidoptera…...227

 

38b.    Body not covered with scales; beak not coiled; antennae variable, but often short, with 3 or

           less segments [wingless flies]......................................................................................Diptera.………..88

 

39a (37b).    Mouthparts in the form of a cone located basally on ventral side of head; palps

                 present but short; body elongated, usually <5 mm in length; antennae about as long as

                 head and prothorax combined, not bristle-like, and 4-9 segmented; tarsi 1-2 segments,

               often without claws (Fig.A) [thrips....... A.......................................…............….......Thysanoptera

 

39b.    Mouthparts as an elongated segmented beak; palps absent; other characters variable.……........40

 

40a (39b).    Beak arises from front part of head; antennae with 4-5 segments and not bristle-like;

                 tarsi usually with 3 segments; abdomen without cornicles (= dorsal tubular structures on

               posterior abdomen ) [true bugs]. ... A......................................Hemiptera / Heteroptera.....….140

 

40b.    Beak arises from rear of head; antennae either with >5 segments (and tarsi with 2

segments) or bristle-like (and tarsi with 3 segments); abdomen often with a pair of

               cornicles (Fig.A) [aphids, hoppers, etc.]...............................................................................Homoptera

 

41a (36b).    Abdomen very constricted at base; antennae often elbowed; tarsi with 5 segments;

                   bodies hard, ant-like [ants & wingless wasps]................................................Hymenoptera.....118

 

41b.    Abdomen not very constricted at base; antennae not elbowed; tarsi variable..............……..........42

 

42a (41b).    Abdomen with 3 long thread-like caudal filaments and with style-like appendages on

some abdominal segments (Fig.A); mouthparts mandibulate, but often somewhat   A

               retracted into head; body almost always covered with scales; terrestrial [bristletails].….....…..43

 

42b.    Abdomen with only 2 thread-like caudal filaments or none; if with 3 [mayfly nymphs]

           then aquatic; other characters variable................................................................................……….......44

 

43a (42a).    Compound eyes large and usually contiguous; body somewhat cylindrical, with

                 thorax arched; ocelli present; middle and hind coxae often with styli; abdominal styli (=

               bristlelike processes) on segments 2-9 (Fig.A).... A..........................……..............Microcoryphia  

 

43b.    Compound eyes small and widely separated or absent; body somewhat flattened

 dorsoventrally, thorax not arched; ocelli present or absent; middle and hind coxae without styli;

 abdominal segments 1-6 (sometimes 7) without styli (Fig.A) [silverfish] ……......…..Thysanura

 

44a (42b).    Aquatic insects, often with tracheal gills (= protruding externally at spiracles ).….......…...45

 

44b.    Terrestrial insects, without tracheal gills.................................................................……...........….........52

 

45a (44a).    Nymphs; compound eyes and usually wing pads present..............................……...................46

 

45b.    Larvae; compound eyes and wing pads absent..........................................................……...................48

 

46a (45a).    Prehensile labium (= lower lip), folded under head at rest, and when extended much

                   longer than head (Figs.A-G) [dragonfly and damselfly nymphs]...... A...…................Odonata

 

46b.    Labium normal, not as previously described...............................................................……...................47

 

47a (46b).    Having 3 caudal filaments; tarsi with 1 claw; gills located on lateral margins of

                   abdominal terga (= dorsal plates or sclerites)  and usually leaflike or plate-like  A

                   (Figs.A-C) [mayfly nymphs]........................................................................................Ephemeroptera

 

47b.     With 2 caudal filaments; tarsi with 2 claws; gills mostly present, somewhat fingerlike,

            usually located on underside of thorax (Figs.A-D) [stonefly nymphs]..............................Plecoptera

 

48a (45b).    Having 5 pairs of prolegs (= fleshy abdominal legs) on ventral side of abdomen, the

                   prolegs with tiny hooks (crochets) [aquatic caterpillars].................................Lepidoptera.....227

 

48b.    Abdominal segments without prolegs or with only one terminal pair..........................…........….....49

 

49a (48b).    Mouthparts with 2 slender and elongated structures, longer than head; antennae long

                 and slender, or least 1/3rd as long as body; tarsi with 1 claw (Fig.A); live in freshwater

               sponges [Sisyridae larvae]..... A.........................................................Neuroptera.….................194

 

49b.    Mouthparts, and usually also antennae, short and not as described previously.........…...….......50

 

50a (49b).    Tarsi with 2 claws; abdomen with long slender lateral processes and a long slender

terminal process (Figs A & B) [Sialidae] or with slender lateral processes and a pair of hooklike structures

 apically (Fig. C.) [Corydalidae, fishfly and alderfly larvae]...... A...........................Neuroptera.....194

 

                  50b.    Tarsi with 1-2 claws; if with 2, then abdomen not as described previously.......................................51

 

 

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Key continues with <insect2.htm>

 

 

 

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NOTE:

 

     Illustrations were simplified, corrected and/or updated to suit the present key. 

       However, please refer to cited authors for greater detail.