Lab 11. Identification: Hemimetabolous Insects

In this lab you will learn to use spot ID characters for identifying selected families of hemimetabolous insects and you will use the dichotomous key by Bland and Jaques to identify the hemimetabolous insects in your collection.

Objectives

The main objectives of this lab are to help you:

  1. learn to identify selected families of hemimetabolous insects based on key characters
  2. identify (to family) the hemimetabolous insects that you will submit with your insect collection.

Activities

1. Assemble your insect specimens, microscope, cork observation block, and labeling equipment.

Your insects should already be pinned, pointed, or spread according to the Insect Collection Instructions.  Each specimen should have a Date/Locality label showing where, when, and by whom it was collected (see Collection Instructions).  Handle your specimens with great care.  Once they are dry, they become very brittle.  Use the cork observation block to position your specimens for viewing under the microscope; it helps reduce accidental breakage.

2. Identify dragonflies and damselflies – order Odonata.

Use How to Know the Insects by Bland and Jaques as an identification guide.  The key to families of Odonata begins on page 71.

Couplet #1 separates dragonflies (suborder Anisoptera) from damselflies (suborder Zygoptera).  The distinction is based on the shape of the hind wing:  broad at the base in dragonflies and narrow at the base (petiolate) in damselflies (see Figure 70).

Dragonflies key out in couplets 2-7.  Damselflies key out in couplets 8-10.  The arculus and nodus (see Figure 70) are features of wing venation that can be used as landmarks to locate important features of venation.  In dragonflies, look for similar triangles near the arculus.  In damselflies, look for the origin of the M3 vein near the nodus.

SpotID  —  You will NOT be asked to identify any families of Odonata on the lab practical.

3. Identify grasshoppers, katydids, and crickets – Order Orthoptera

Use How to Know the Insects by Bland and Jaques to identify your insects.  The key to families of Orthoptera begins on page 91.  Be sure you can distinguish between three-segmented and four-segmented tarsi.  Do NOT count the arolium (an adhesive pad between the claws) as a tarsal segment and don’t confuse the pads beneath the segments with the segments themselves.  Some tarsal segments may have more than one ventral pad.

SpotID  —  Learn to recognize and distinguish the members of Orthoptera that belong to the following three families:

Family Key characters
Acrididae — grasshoppers and locusts
  • short antennae (shorter than body)
  • three-segmented tarsi
  • tympana located on sides of first abdominal segment
Tettigoniidae — katydids
  • long, filiform antennae (longer than body)
  • four-segmented tarsi
  • tympana located on tibiae of front legs
Gryllidae — crickets (house crickets,
field crickets, and tree crickets)
  • long, filiform antennae
  • three-segmented tarsi
  • tympana located on tibiae of front legs

4. Identify true bugs – Order Hemiptera, suborder Heteroptera

All true bugs have a tubular proboscis (beak) that arises from the front of the head.  This proboscis may be short and aimed forward (as in water scorpions or giant water bugs), or it may be long, segmented and, when not in use, curved backwards beneath the head (as in stink bugs and assassin bugs).  Forewings (hemelytra) are leathery or parchment-like at the base and membranous toward the apex.  At rest, they fold over the insect’s back to form an “X”.

Use How to Know the Insects by Bland and Jaques as an identification guide.  The key to families of suborder Heteroptera begins on page 134.

Errors/Corrections —  Make the following changes or corrections in the key to Heteroptera:

24a  —  Revise punctuation to read:  Lips around scent gland openings (on side of thorax between middle and hind coxae) greatly reduced or absent;

SpotID  —  Learn to recognize and distinguish the members of Heteroptera that belong to the following six families:

Family Key characters
Belostomatidae — giant water bugs
  • short proboscis
  • single claw on front legs
  • broad, flat dorsal surface of body
Gerridae — water striders
  • long legs
  • claws ante-apical
  • fringe of hairs at tip of tarsus
Notonectidae — backswimmers
  • keel-shaped dorsal surface
  • ventral surface darker in color than dorsal surface
  • fringed hind legs lack claws
Reduviidae — assassin bugs
  • three-segmented proboscis
  • head elongate, narrowing behind eyes
  • groove along midline of prosternum
Miridae — plant bugs
  • ocelli absent
  • wings angle down behind abdomen
  • cuneus present on front wings
Pentatomidae — stink bugs
  • shield-shaped body
  • five-segmented antennae
  • large, triangular scutellum

5. Identify insects in the order Hemiptera, suborder Homoptera

The suborder Homoptera includes cicadas, leafhoppers, treehoppers, froghoppers (spittlebugs), planthoppers, psyllids, whiteflies, aphids, mealybugs, and scale insects.  All of these insects feed on plants.  They have piercing-sucking mouthparts in the form of a short proboscis (beak) that arises near the back of the head, just in front of the forelegs.  In profile (side view), the head of these insects often has a characteristic “wedge” shape with a blunt frons protruding in front of the eyes.  Forewings are uniform in texture – entirely membranous or entirely parchment-like.  At rest, they usually fold tent-like over the abdomen.

Use How to Know the Insects by Bland and Jaques as an identification guide.  The key to families of Homoptera begins on page 157.

Errors/Corrections —  Make the following changes or corrections in the key to Homoptera:
2a  —  Substitute:  Ocelli located on dorsal sclerite (vertex) or frontal sclerite (frons)  …… 9
2b  —  Substitute:  Ocelli located on lateral sclerite (gena) …… Superfamily Fulgoroidea (STOP HERE – use this superfamily name for your specimens)

16b  —  …………………. Superfamily Coccoidea (STOP HERE – use this superfamily name for your specimens)

18b  —  ………………….. Superfamily Aphidoidea (STOP HERE – use this superfamily name for your specimens)

SpotID  —  Learn to recognize and distinguish the members of Homoptera that belong to the following six families (or superfamilies):

Family Key characters
Cicadidae — cicadas
  • large body size
  • three ocelli
Cicadellidae — leafhoppers
  • comb-like rows of long spines along tibiae of hind legs
Cercopidae — spittlebugs
(froghoppers)
  • large bristles clustered at the distal end of each leg segment
Membracidae — treehoppers
  • large pronotum covers head and extends backwards over abdomen
Aphidoidea (superfamily) — aphids
  • cornicles
  • soft-bodied
Coccoidea (superfamily) — scale insects
  • sessile, sac-like body
  • covered by protective “shell”

Materials

You will need the following materials for this lab:

  • Your collected insects
  • How To Know The Insects  3rd edition,  by R. G. Bland and H. E. Jaques
  • Stereoscopic microscope or hand-held magnifier
  • Date/Locality labels
  • Labeling pen
  • Step Block
  • Cork observation block

Getting help

For help with identification, you can post pictures to the “What’s This” discussion board or bring insects to lab or office hours.  Either way, be sure to note where and when the specimen was collected — that often helps narrow down the possibilities.

Grading considerations

Your collection will be graded according to the checklist in the “Collection Instructions”.  Please note the following points:

All adults in the orders Odonata, Orthoptera, and Hemiptera (that you submit for grading) must be identified to “family”.  It is not required that adults in other hemimetabolous orders (e.g. Plecoptera, Dermaptera, Psocodea, etc.) be identified to family level, but you can earn family credit for any specimens that are labeled with the correct family name.  In some cases, family identity is easy to determine (all praying mantids are Mantidae, for example).  In other cases, the family may be difficult to determine without high magnification or special mounting techniques.  Don’t waste a lot of time on these insects – just give the order name.

If an adult has been preserved in alcohol, be sure to include the word “adult” on its ID label.  You will lose two points on your collection grade for each adult in alcohol that does not bear this label.

The specimens you submit for grading should be in relatively good condition.  I don’t expect perfection, but all insects should have the head, thorax, and abdomen intact.  A few missing or broken appendages are acceptable as long as the corresponding part on the opposite side of the body is still present (i.e. one of everything!).  You may use clear nail polish to glue broken appendages back on to the body as long as you do it neatly.

Family ID labels should be located under the date/locality labels and aligned parallel with the long axis of the insect’s body (or long axis of the paper point).

Ecology labels are optional.  If present, they should be located under the family ID label and down against the pinning surface of your collection box.

You will lose points on your collection grade for any of the following mistakes:

  • Date/locality label missing or formatted incorrectly.  See “Collection Instructions”.
  • ID label missing or incorrect.  See “Collection Instructions”.
  • More than one ecology label.  For specimens that fulfill more than one ecological category, put all key words on a single label.
  • Failure to use “permanent” black ink for labels.
  • Immature specimen is pinned without “immature” appearing on the ID label.
  • Adult specimen is in alcohol without “adult” appearing on the ID label.