Fig. 7.2 Gullen & Cranston, 2005 A current hypothesis for the cladistic phylogeny of the insects and...
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Transcript of Fig. 7.2 Gullen & Cranston, 2005 A current hypothesis for the cladistic phylogeny of the insects and...
Fig. 7.2Gullen & Cranston, 2005
A current hypothesis for the cladistic phylogeny of the insects and primitive hexapods
“basal orders” (= “Apterygota”)
NEW ORDER! ca. 2000
“primitive hexapods”?
??
true INSECTS
ARCHAEOGNATHA (= MICROCORYPHIA)
jumping bristletails
THYSANURA (= ZYGENTOMA)
silverfish, firebrats
The Basal or Apterygote (wingless) Orders
ARCHAEOGNATHA
Shrimp-like profile; tail filaments relatively parallel, bristly. Primitive, spider-like, single-articulated jaws. Deocmposers. No economic significance.
“Jumping bristletails”
X-sec
Thermobia, a firebrat. Giant neurons in tail filaments studied at UW.
THYSANURA (ZYGENTOMA)“silverfish & firebrats”
Flattened profile, don’t jump, tail filaments held close to 90 deg. apart. A few are economic pests, damaging cellulose & fabric.
“Aquatic” Insects
A polyphyletic, ecological assemblage of taxa.
The aquatic lifestyle has arisen many times in insect evolution; only in a few orders is it the rule.
In most, the immature stages are truly aquatic while the adult is a winged terrestrial form.
Holometabolous, Endopterygote
Hemimetabolous, Exopterygote
Paleoptera
AQUATIC INSECTS, an ecological (polyphyletic) group
otherorderswithaquaticspecies
TRICHOPTERA
PLECOPTERA
ODONATAEPHEMEROPTERA
Importance of Aquatic InsectsMost references to nymphs/larvae; some taxa beyond this lecture
Natural World Nutrient cycle: decomposers
Water quality: filter feeders
Food Webs: prey & predators, e.g. salmon fry eat bugs
Anthropophilic World
Aquatic environmental quality indicators
Medical/Disease vectors, especially mosquitoes, other flies
Human Food (coryxid eggs; water bug wing muscle; fly pupae)
Sport Fishing (Fly Tying)
Life History & Physiological Aspects ofAquatic vs. Terrestrial Insects
Development Terrestrial: variable rateAquatic: Generally slower (colder temperature under water)
Water/Ion Balance Terrestrial: conserve water from dehydration Aquatic: conserve ions from dilution
Respiration Terrestrial: open system (siphon, physical gill, etc.)Aquatic: closed tracheal system (gills, cutaneous) with exceptions
Nitrogen Waste Removal Terrestrial: uric acid (conserves water) Aquatic: ammonia (conserves energy)
EPHEMEROPTERA, mayflies
aquatic immature
terrestrial (winged) adult
Fish-eye view through the mind of the fisherman (superpredator). Fish as entomologists!
Adult
gills
wing pads
3 “tail filaments” = cerci
Larva (nymph, naiad)
gill covers
Mayflies are predaceous or detritovores as nymphs. Adults do not feed.
forlegs
Mayfly adult antennae are small; hindwing may be small or vestigal.
hindwing
larval molt, subimago molt, & adult
ODONATA, dragon- & damselflies
damselflies
dragonflies
labial mask
All odonates are predators as both nymphs and adults.
1. lunge
2. grab
dragonfly larva labial mask hydraulic feeding mechanism
Some large dragonfly nymphs may take vertebrate prey!
adult eclosion
tracheal tubes
A tropical dragonfly. The wings are always held out at rest.
• Dragon flies have acute and fast vision.
• Up to 10,000 eye facets (high resolution!)
• Adaptations: small prey capture at high speed while flying & mate/mate competitor detection.
Well-known “loop” configuration of mating odonates; male grasps female with tail claspers; transfers sperm from secondary sex organs on 2nd abdominal segment.
A damselfly. Some are spider predators.
Males of some dragonfly species are territorial, with traditional perches.
Some ancient dragonfly relatives (“Griffinflies”) measured over two feet in wingspan. How could flying insects live at this scale?
PLECOPTERA, stoneflies
• Orthopteroids i.e., cricket- or roach-like.
• Nymphs fully aquatic, prefer highly oxygenated water.
• Thoracic gills.
• Two long cerci in nymphs & adults.
Stoneflies are predators or detritovores as numphs; adults do not feed.
thoracic gills
Some insects can be active at near-freezing temperatures. A “winter” stonefly nymph, one species among various snow-active insects.
wing pads
Stonefly exuviae.
TRICHOPTERA, caddisflies
hairy (vs. scaly) wingslong, thread-like antennae
reduced mouthparts
Features distinguishing adult caddisflies from adult moths.
wings membranous (~transparent)
• Sister order to the Lepidoptera.• Moth-like.
A true moth.
scales
diverse larval cases (including none!)
Caddisfly nymphs are predaceous or detritovores; adults do not feed.
TRICHOPTERA
caddis fly larval cases
typical caddisfly larva without case
from Gullen & Cranston 2000
Life stages of an aquatic snout moth (Pyralidae).Parallel evolution of the caddisfly-like natural history.
Marine Insects
all from Cheng 1976
Halobates, an open water predaceous bug.
Egg phoresy: eggs laid on tail of seabird.
Hydrophobic hairs on tarsi of Trochopus, a related genus.
Clunio californiensis, an open water marine midge (DIPTERA: Chironomidae)
male skating
mating behavior
male
female
all from Cheng 1976
• Sea skaters, genus Halobates, are the only insect known to live in the open ocean. More than 40 species have been described, but only five (H. micans, H. sericeus, H. sobrinus, H. germanus and H. splendens) are oceanic (Andersen & Cheng 2004).
–
Their overall range lies between 40°N and 40°S, but within that expanse each species has a different specific range (Cheng 1989). In the eastern tropical Pacific Ocean (ETP), four of five oceanic species can be found; H. germanus occurs in the Indian and western Pacific oceans (Andersen & Cheng 2004). Sea skaters have been reported thus far in the diet of more than a dozen surface-feeding seabirds.
END