| 
   
    | 1a.    Adults have well-developed wings |    
   
    | 1b.    Adults wingless or with wings vestigial or rudimentary
    (nymphs, larvae & some adults) |   \ 
   
    | 2a (1a).    Wings
    membranous, not hardened or leathery |    
   
    | 2b.    Front wings hardened or leathery, at least at base (Figs.A-E); hind wings, if present, usually
    membranous . . . . A |    
   
    | 3a (3a).    Only 1 pair of
    wings |      
   
    | 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  <Habits>; <Adults> & [Latest Classification[ |    
   
    | 4b. Body not shaped like a
    grasshopper;  pronotum not as
    previous; hind legs not so enlarged.  |      
   
    | 5b.     Does not fit previous description exactly  |    
   
    | 6a (5b).    Abdomen with 1-3
    thread-like or bristle-like caudal (= tail)
    filaments; mouthparts vestigia |    
   
    | 6b.     Abdomen without thread-like or
    bristle-like caudal filaments; mouthparts almost always developed,
    mandibulate (= chewing)  or for sucking |    
   
    | 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  <Habits>  [Latest
    Classification] |    
   
    | 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  <Habits> [Latest Classification] |      
   
    | 8b.    Tarsi with 2-3-segments; mouthparts
    variable; hind wings reduced or absent, not haltere-like |          
   
    | 10b.    Wings not covered with scales; mouthparts
    not a coiled proboscis, antennae variable |      
   
    | 11b.    Wings not as previously described , or
    if wings are somewhat linear, then the tarsi have more than 2 segments |    
   
    | 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  <Habits> [Latest Classification] |    
   
    | 12b.    Not as previously described |    
   
    | 13a (12b).    Tarsi with 5
    segments |    
   
    | 13b.    Tarsi with 4 or less segments |      
   
    | 14b.    Front wings not hairy, at the most with
    microscopic hairs; mandibles well developed; antennae shorter than body |    
   
    | 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  
    <Habits>  [Latest
    Classification] |    
   
    | 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 |    
   
    | 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  
    <General Characateristics>  [Latest Classification] |      
   
    | 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   <Habits>; <Adults> & <Juveniles>  [Latest
    Classification] |    
   
    | 17b.    Not as previously described |    
   
    | 18a (17b).    Mouthparts for
    sucking |    
   
    | 18b.    Mouthparts mandibulate (= chewing) |    
   
    | 19a (18a).    Beak arises from
    front part of head (Figs.A-E) [gnat bugs..Hemiptera /Heteroptera ...... A |        
   
    | 20b.    Tarsi with 3 or less segments; hind
    wings usually shorter than front wings; cerci either present or
    absent |    
   
    | 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  <Habits>; <Adults> &  <Juveniles>  [Latest
    Classification] |    
   
    | 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 |      
   
    | 22b.    Tarsi with 2-3 segments, basal segment of front tarsi not
    enlarged |      
   
    | 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 (= Corrodentia) |    
   
    | 24a (2b).    Mouthparts for
    sucking, beak elongated and usually segmented (Figs.A-B)...... A |    
   
    | 24b.    Mouthparts mandibulate |    
   
    | 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   <Habits>  [Latest
    Classification] |    
   
    | 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  
    <Habits>  [Latest
    Classification] |      
   
    | 26b.    Abdominal cerci not like forceps, or
    if cerci appear as such, then front wings cover most of abdomen; tarsi
    variable |    
   
    | 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  
    <Habits>  [Latest
    Classification] |    
   
    | 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   <Habits>;
    <Adults> & <Juveniles>  [Latest
    Classification] |    
   
    | 28a (1b).    Body usually
    insect-like, with segmented legs and usually segmented antennae |    
   
    | 28b.    Body generally worm-like, body regions
    (except possibly head) not well differentiated, and segmented thoracic legs
    absent; antennae present or absent |      
   
    | 29b.    Wings entirely absent or with 4 rudimentary wings and no halteres;
    tarsi variable |      
   
    | 30b.    Antennae usually present (sometimes small); size and
    habitat variable.......... |    
   
    | 31a (30b).    Ectoparasites of birds,
    mammals, or honey bees and usually found on the host; body somewhat
    leathery and usually flattened dorsoventrally or laterally |    
   
    | 31b.    Free-living (not ectoparasitic), terrestrial or aquatic |    
   
    | 32a (31a).    Tarsi with 5
    segments; antennae short and usually concealed in grooves on head; mouthparts
    for sucking |    
   
    | 32b.    Tarsi with fewer than 5 segments; antennae and mouthparts variable |          
   
    | 34b.    Antennae not longer than head; tarsi with 1 segment |    
   
    | 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   <Habits>  [Latest Classification] |      
   
    | 36a (31b).    Mouthparts for sucking,
    with a conical or elongated beak enclosing stylets |    
   
    | 36b.    Mouthparts mandibulate (sometimes hidden in head), not
    beaklike |    
   
    | 37a (36a).    Tarsi with 5 segments;
    maxillary or labial palps ( = segmented processes) present |    
   
    | 37b.    Tarsi with 4 or fewer segments; palps small or absent  |        
   
    | 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  
    <Habits>;
    <Adults> & <Juveniles>  [Latest
    Classification] |    
   
    | 39b.    Mouthparts as an elongated segmented beak; palps absent;
    other characters variable |    
   
    | 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   <Habits>  [Latest
    Classification] |    
   
    | 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  
    <Habits>  [Latest
    Classification] |    
   
    | 41a (36b).    Abdomen very constricted
    at base; antennae often elbowed; tarsi with 5 segments; bodies
    hard, ant-like [ants & wingless wasps ........ Hymenoptera   <Habits>  [Latest Classification] |    
   
    | 41b.    Abdomen not very constricted at base; antennae not elbowed;
    tarsi variable |    
   
    | 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] |    
   
    | 42b.    Abdomen with only 2 thread-like caudal
    filaments or none; if with 3 [mayfly nymphs] then aquatic; other characters
    variable  |    
   
    | 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 ......Class:
    Insecta; Subclass Monocondylia: Order: Arachaeognatha..…….... 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  <Habits>; <Adults> & <Juveniles>  [Latest
    Classification] |    
   
    | 44a (42b).    Aquatic insects,
    often with tracheal gills (= protruding externally
    at spiracles) |    
   
    | 44b.    Terrestrial insects, without tracheal gills |    
   
    | 45a (44a).    Nymphs; compound
    eyes and usually wing pads present  |    
   
    | 45b.    Larvae; compound eyes and wing pads
    absent |      
   
    | 46b.    Labium normal, not as previously described  |    
   
    | 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  
    <Habits> [Latest Classification] |      
   
    | 48a (45b).    Having 5 pairs of
    prolegs (= fleshy abdominal legs) on ventral side of
    abdomen, the prolegs
    with tiny hooks (crochets) [aquatic caterpillars) ............ Lepidoptera   <Habits>  [Latest
    Classification] |    
   
    | 48b.    Abdominal segments without prolegs or with only one
    terminal pair  |      
   
    | 49b.    Mouthparts, and usually also antennae, short and not as
    described previously |      
   
    | 50b.    Tarsi with 1-2 claws; if with 2, then abdomen not as
    described previously  |  
 |