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Phylum Arthropoda: Sub-phylum Uniramia (insects, centipedes, and millipedes)
I. Sub-phylum Uniramia (insects & myriapods = centipedes & millipedes)
A. uniramous appendages: unbranched
B. primarily terrestrial
1. one pair of antennae, mandibles, and one or two pair of maxillae.
C. Class Insecta (hexapoda); 750,000 known spp.
1. greatest diversity of species, habitats, and ecology
a. reasons for success: small size, terrestrial reproduction, exoskeleton,
locomotion, sensory & behaviors
b. entomology = the study of insects
c. key insect characteristics:
1. external skeleton composed of chitin; sclerites (plates); flexible
between
2. jointed appendages; (3) pairs of legs on thorax
3. segmentation & tagmata:
a. Head- compound eyes (ommatidia), ocelli, & mouthparts
(labrum, mandibles, maxillae, & labium)
b. Thorax- wings (1-2 pair) & legs (3 pair)
c. Abdomen- no appendages; reproduction/digestion
4. complex behaviors
d. structure & function
1. digestive system: foregut, midgut, & hindgut
2. phytophagy, saprophagy, predatory, & parasitic
3. mouthparts: biting/chewing & sucking
4. respiratory exchange: tracheal system & spiracles, diffusion, &
abdominal gills
5. osmoregulation: Malpighian tubules typical
6. reproduction: dioecious, internal fertilization, mate attraction, &
parthenogenesis
7. metamorphosis & growth:
a. hemimetabolous = incomplete metamorphosis; examples
include: grasshoppers, true bugs, & roaches
b. holometabolous = complete metamorphosis (most insects);
examples include: moths, beetles, & flies
c. diapause
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II. Insect Orders:
A. Order Coleoptera
1. Characteristics
a. hard sclerotinized body in adults
b. well developed eyes
c. mandibulate (chewing mouthparts)
d. elytra-hard wing covers
e. hind legs modified for swimming
f. Dytiscidae and Hydrophilidae have self contained air reserves.
g. larvae with distinct sclerotinized head
h. gill like lateral appendages in some larvae
2. Life History
a. many predaceous forms, scavengers
b. interesting and complex behaviors
c. pupal stage generally terrestrial
d. holometabolous
e. 3-8 instars
f. adults overwinter
g. oviposition in water on aquatic vegetation
h. univoltine in temperate zones
i. Hydrophilidae carry egg masses on abdomen
3. Taxonomy
a. diverse group with a large number of species
b. 30,000 species in N. America
1. 1,000 aquatic or semiaquatic
c. 6,000 aquatic world wide (27 families)
d. mouthparts important in classification
4. Habitat
a. most species are terrestrial
b. some adults and larvae reside under water
c. fresh, brackish, and marine forms
5. important families
a. Gyrinidae-whirlygig beetles
b. Elmidae- scraper/herbivore
c. Dytiscidae- swimmer
d. Hydrophilidae- swimmer
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B. Hemiptera (water bugs)
1. characteristics
a. wings arranged in "X" pattern- thick forewing; membranous distal
b. sucking mouthparts
1. predators
2. scavengers
c. some with slender elongate body
d. some with dorsoventral flattening
2. life history
a. incomplete, gradual metamorphosis
b. adults overwinter
3. Taxonomy
a. 15-17 families N. America (404 species)
b. 3,200 species are aquatic or semiaquatic worldwide.
4. Habitat
a. nektonic- in water
b. epineustonic
c. shoreline
5. Families
a. Gerridae
b. Veliidae
c. Corixidae
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C. Order Diptera
1. Characteristics:
a. maggot like larvae
b. reduction of head
c. wing pads absent
d. larvae with prolegs and crochets
e. adults with one pair of membranous wings
f. respiratory siphons
g. labrial fans
2. Life History:
a. transmit serious disease
b. holometabolous
c. 3-4 larval instars
d. larvae or eggs overwinter
3. Habitat:
a. important in arctic tundra regions
b. inhabit many diverse habitats
c. inhabit areas with extreme environmental conditions
d. both free swimming and attached forms
e. live in swift current (Simulidae)
4. Families:
a. Chironomidae
b. Simulidae
c. Tipulidae
d. Tabanidae
e. Chaoboridae
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D. Order Lepidoptera
1. characteristics
a. pupae develop within cocoons
b. construct silk retreats
2. life history
a. holometabolous
b. larvae overwinter
c. adults short lived (24 hours-2 months)
3. Taxonomy
a. > 10,000 sp. in N. America, most terrestrial
b. 50 sp. aquatic N. America
c. 100 sp semiaquatic
4. habitat
a. attached to rocky substrates, macrophytes, and emergent plants
b. boring into plants
E. Order Megaloptera
1. characteristics
a. predatory and cannibalistic forms
b. elongate and flattened
c. eggs and egg masses diagnostic
2. life history
a. adults are short lived
b. holometabolous
3. taxonomy
a. Sialidae (alderflies)
b. Corydalidae (dobsonflies)
c. < 300 species worldwide
4. habitat
a. lotic and lentic forms
b. tropical and temperate
c. burrowers inhabit soft substrates and detritus
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F. Order Odonata
1. Characteristics
a. adults with large compound eyes
b. labium
2. Life History
a. nymphs exclusively carnivorous
b. last nymphal instar leaves the water to undergo final ecdysis.
c. complex reproductive behavior
d. tropics=multivoltine; temperate regions= univoltine
e. 10-15 instars
3. Taxonomy
a. SO Anisoptera= dragonflies; SO Zygoptera= damselflies
b. 5,500 species worldwide
c. 650 species in N. America
4. Habitat- most diverse in lentic environments
5. important families
a. Gomphidae
b. Calopterygiidae
c. Coenagrionidae
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G. Order Epemeroptera
1. Characteristics:
a. herbivorous & detritivores
b. 10 segmented abdomen
c. most species with three caudal filaments
2. Life History:
a. hemimetabolous
b. ephemeral adult stage 2-3 days
c. adults do not feed
d. multivoltine (2+ generations per year); univoltine in temperate regions
e. eggs deposited at the water surface
3. Taxonomy:
a. 2000 species (22 families) worldwide
b. 650 species N. America
4. Habitat:
a. highest diversity in warm lotic waters
b. prefer rocky bottom (1-3) order streams
c. collectors and scrapers
5. important families:
a. Oligoneuriidae
b. Baetidae
c. Heptageniidae
d. Caenidae
6. nymph types:
a. swimming
b. climbing/creeping
c. flattened/streamlined
d. burrowing
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H. Order Plecoptera
1. Characteristics
a. most with two caudal cerci
2. Life History
a. hemimetabolous
b. terrestrial adults
c. most herbivorous (shredders); some carnivorous
d. adults live 1-4 weeks
3. Taxonomy
a. 2000 species worldwide
b. 540 species in N. America
4. Habitat
a. mostly temperate regions
b. no marine forms
c. clean, cold waters and oligotrophic lakes
5. important families
a. Perlidae
I. Order Trichoptera
1. characteristics
a. abdomen with nine segments usually entirely membranous.
b. often with heavily sclerotized pupal mandibles
2. life history
a. holometabolous
b. adults active; winged
c. larvae of many species occur in cool, lotic waters
d. most larvae eat plant material and algae
e. larvae construct nets, retreats, or cases
3. Taxonomy
a. 1,200 species in North America (145 genera, 21 families)
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J. Class Diplopoda (millipedes); 10,000 spp.
1. slow moving; nocturnal; detritivores
2. two pairs of legs per segment
3. chewing mouthparts; herbivores
4. repugnatorial glands
K. Class Chilopoda (centipedes); 2500 spp.
1. fast moving; carnivores; maxillipeds w/ venom
2. one pair of legs per segment
3. dorso-ventrally flattened
4. negatively phototactic; nocturnal
5. especially diverse in tropics
6. repugnatorial glands