Review Sheet -- Test 2 (Week 7) Biology 1224 -- Entomology; James Adams
Infraclass Neoptera; Division Endopterygota; Superorder Neuropteroidea
Order Coleoptera --
The Beetles (Chapter 39)
Tiny to large insects; typically with decent sized compound eyes (with exceptions);
mandibulate, with mandibles, maxillae and labium well developed. Prothorax large, mobile,
notum extending ventrally nearly to coxal base; meso- and metathorax often fused ventrally;
small mesoscutellum always visible; forewings heavily rigidly sclerotized as elytra, often with
visible longitudinal "venation"; elytra strongly interlocking along back; hindwings membranous;
used for flight (not in flightless forms . . . DUH!). Abdominal sternites also well sclerotized for
protection; tergites weakly sclerotized (but typically covered by elytra at rest); no cerci.
Generally, females and males similar (with exceptions). Stridulatory sounds made by a few
families, not only for courtship, but also in response to being handled (such as the cerambycids
[longhorn beetles]). Number of eggs laid, location of egg-laying, etc., is quite variable
depending on families; a few species dig chambers for eggs (dung beetles), and stock
chambers with resources for the larvae.
Larvae variable between families; typically have a sclerotized head capsule; mandibulate;
thoracic segments with legs with 4 or 5 tarsal segments bearing terminal claws; abdomen often
bearing sclerotized movable urogomphi on terminal segments. Most are of limited mobility and
grublike, but predatory forms are quite active, and parasitic forms are similar to the Strepsiptera,
with an active first instar that becomes very non-motile in later instars on the host (see page 457
for discussion of the different larval body forms). Pupae adecticious and exarate in most;
pupation usually occurs in a cell in the feeding substrate or somewhere nearby.
This order is incredibly diverse (the most diverse order); beetles have exceedingly variable
life styles. The majority are terrestrial herbivores, though several families are entirely predatory,
some parasitic, in both terrestrial and aquatic environments. Even among the herbivores, there
are seed, stem, leaf, root, gall, and plant litter specialists, as well as a few (cantharids -- the
soldier beetles) that make use of pollen/nectar. There are fungal specialists. Some species
inhabit ant and termite colonies, others make use of dung or carrion. There are a number that
are of economic importance in crops, forests, and households.
The success in the diversity of this order probably lies to a large extent in the protection
afforded by the heavily sclerotized elytra and underside of the body. The body is often compact,
with abdominal segments shortened or reduced in number, and the head often "tucked" into the
thorax. Legs/antennae may often be retracted into grooves on the body for even further
protection. This heavily sclerotized body is also very effective at preventing water loss, and
many species of beetles may be a conspicuous part of the insect fauna in arid habitats. Many
species are often further protected by chemicals that are stored in the body, and many of these
can ooze or spray noxious compounds onto potential predators, such as coccinellids [ladybugs],
carabids [ground beetles], lampyrids [lightning bugs], cantharids, lycids [net-winged beetles],
meloids [blister beetles], silphids [carrion beetles], just to name a few you may encounter.
Several species (lampyrids, phengodids [glowworm beetles], some elaterids [click
beetles) are some of the most familiar bioluminescent organisms in the world.
This is the largest order of insects, with over 300,000 species described worldwide, and
the number could be quite a bit higher. Six separate families (see below) number more than 20,000
species, and, among these, the Curculionidae (weevils) number a bit more than 60,000 species.
Suborders (that you are likely to encounter):
Adephaga -- typified by first visible abdominal sternite being divided by immovable coxa
of third leg; prothorax with some extra pleural sclerites; tarsal segmentation 5-5-5; typically
large round eyes, necessary for the predatory life-style of most of these beetles; abdomen with
six visible sternites.
Likely encountered families in the Adephaga include:
*Carabidae: Ground Beetles & Bombardier beetles; many can secrete extremely
foul smelling fluids, Bombardier beetles secrete hot fluids; 3rd largest family.
*Cicindelidae: Tiger Beetles; fast running predators, also adept flyers in most cases
*Dytiscidae: Predaceous Diving beetles (somewhat similar to some Hydrophilidae)
Gyrinidae: Whirligig Beetles; gregarious on the water= s surface; clubbed antennae
Polyphaga -- pronotum without extra sutures (no extra sclerites); first abdominal segment
not divided by coxae; the posterior margin of this abdominal segment visibly extends completely
across abdomen; tarsal arrangement variable; lifestyles variable; 90% of all beetles.
Likely encountered families in the Polyphaga include:
*Hydrophilidae: Water Scavenger Beetles, some large and similar to dytiscids
Histeridae: Hister Beetles
Leiodidae: Round Fungus Beetles; small, usually black, and associated with fungi
*Staphylinidae: Rove Beetles; long, narrow, short elytra; superficially similar to
Dermaptera and Embioptera; 2nd largest family of beetles.
*Silphidae: Carrion Beetles; as name suggests, often associated with carrion; large;
bad smelling and brightly colored
*Lucanidae: Stag Beetles; very large with huge mandibles, particularly in males
*Passalidae: Bessbugs or Bess Beetles; large; gregarious in rotting wood
*Scarabaeidae: Scarab Beetles, which include Dung Beetles, Hide Beetles, June
Beetles, Chafers, Shining Leaf Chafers (including Japanese Beetle), Rhinoceros
and Hercules Beetles, and Flower Beetles; very large family (7th largest).
You may also find species in the closely related Geotrupidae and Trogidae.
Rhipiceridae (Sandalidae): Cedar Beetles; rare, but noticeable large, black beetles
*Buprestidae: Metallic Wood Boring Beetles; larvae wood-boring, some adults
however are typically found on flowers
*Elateridae: Click Beetles
Eucnemidae: False Click Beetles
*Cantharidae: Soldier Beetles; soft, colorful elytra; often flower visitors
*Lampyridae: Lighting Bugs
*Lycidae: Net-winged Beetles; long, broad, flexible elytra, often brightly colored
*Phengodidae: Glowworm Beetles; short elytra, with flying wings extending out from
under elytra; males with distinctive feathery antennae
Dermestidae: Dermestid Beetles; circular to slightly oval beetles; typically feed on
remains of animals, including skins; also eat dead insects (as larvae), and
dermestids (along with psocids) are the main pests of insect collections.
Also eat carpets, wool, silk, cereal products -- major economic impact.
Bostrichidae: Branch-and-Twig Borers; can infest stored vegetable products,
wood, bamboo products, etc., and may infest green shoots, weakened trees
Cleridae: Checkered Beetles; most of body surface hairy, wide head
Nitidulidae: Sap Beetles; found on sap and rotting fruit; a few on flowers
*Cucujidae: Flat Bark Beetles; FLAT body, found under bark; a few species may
feed in stored plant products; some species brightly colored
*Erotylidae: Pleasing Fungus Beetles; good sized beetles, often gregarious on fungi;
some remarkably beautiful with brilliant orange markings on shiny elytra
*Coccinellidae: Ladybird Beetles (or Ladybugs); round, with flat ventral surface;
elytra usually spotted; head tucked under leading edge of pronotum;
predaceous, both as larvae and adults, on aphids and scales -- beneficial.
*Tenebrionidae: Darkling Beetles; 5th largest family; found on fungi, under bark
Melandryidae: False Darkling Beetles
Pyrochroidae: Fire-colored Beetles; long, soft, dark elytra; head and prothorax
bright red or orange; antennae plumose.
Oedemeridae: False Blister Beetles; look quite similar to . . .
*Meloidae: Blister Beetles; exude compounds that may blister skin; elytra not
heavily sclerotized, body soft as well.
Mordellidae: Tumbling Flower Beetles; elongate, with tapering abdomen
extending beyond end of elytra; jump/tumble when picked up; found on
flowers and foliage, also in bracket fungi.
*Cerambycidae: Longhorn Beetles; as name suggests, typically with very long
antennae (though there are exceptions); some very large; diverse (6th largest
family); adults plant feeders; larvae wood boring
*Chrysomelidae: 4th largest family; includes Leaf Beetles, Flea Beetles, Tortoise
Beetles; feed almost exclusively on plant materials; some are pests on plants
(Potato Beetle, Cucumber Beetle)
Bruchidae: Seed Beetles; can be pests on stored beans/peas.
Brentidae: Primitive Weevils; relatively large, brown elongate beetles, with
elongate mouthparts; hard elytra
*Curculionidae: Weevils or Snout Beetles; elongate mouthparts; can be incredibly
economically damaging on living crop plants (alfalfa, strawberries, cotton);
Largest family of beetles (as indicated above), and of all insects.
Scolytidae (included in the Curculionidae by many): Bark (or Bark-and-Ambrosia)
Beetles; can be incredibly damaging in timber stands -- in the western U.S., this
family accounts for the loss of 1+ billion board feet of wood annually.