Fig. 7.2 Gullen & Cranston, 2005 A current hypothesis for the cladistic phylogeny of the insects and primitive hexapods “basal orders” (= “Apterygota”) NEW ORDER! ca “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 other orders with aquatic species TRICHOPTERA PLECOPTERA ODONATA EPHEMEROPTERA

Importance of Aquatic Insects Most 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 of Aquatic vs. Terrestrial Insects Development Terrestrial: variable rate Aquatic: 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) wings long, 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

END