Introduction to Insects

1. Introduction to Insects BIO 402: Field Biology Bumblebee on thistle Sumter National Forest May 2005

2. Insects are … JumpStart – September 7, 2010

3. PHYLUM ARTHROPODA Arthropods are characterized by: Exoskeleton of chitin (must molt to grow) Jointed legs Segmented body Variable number of antennae for senses Breath through a number of branching tubulesmarine crab at Riverbanks Zoo

4. PHYLUM ARTHROPODA Two major subphyla are: Subphylum Chelicerata(chelicerates) no antennae mouth parts with chelicerae at least five pair of legs or leg-like appendages two distinct body segmentsInclude: horseshoe crab, sea spiders, arachnids

5. Sea spider (above) Brown recluse spider(right) Horseshoe crab (below)

6. PHYLUM ARTHROPODA Subphylum Mandibulata(mandibulates) Have antennae Mouthy parts with mandibles Widely variable number appendages Variable number of body segmentsInclude: crustaceans, millipedes, centipedes and insects

7. Mosquito (ul) Millipede (ur) Centipede (ll) Crayfish (lr)

8. INSECTS Trivia about insects: Over 1 million species worldwide90% are in the tropics About 13,000 species in North Carolina About 10,000 species in South Carolina Stag Beetle

9. INSECT CHARACTERISTICS Three body segments (head, thorax, abdomen) One pair antennae Mouth parts containing a labrum, pair of mandibles, pair of maxillae, a hypopharynx and a labium Three pair of legs Often 1-2 pair of wings (attached to thorax) A gonopore at posterior end of abdomen No locomotor segments on the abdomen

11. INSECT DEVELOPMENT Insects grow by molting, commonly resulting in change Process leads to metamorphosis

12. METAMORPHOSIS TYPES Several types of metamorphosis Simple – gets large with each molt Gradual – slow development of wings and other structures Incomplete – last molt dramatic:aquatic to terrestrial life Complete – larvae  pupae  adultlarval forms commonly hard to identify

13. Insect Body Structure We will look at the following components: Head Body plates Thorax Wings Legs Abdomen

14. Head structures Compound eyes typically present positioned above or behind the antennae variation present in: size, shape, color Ocelli also present – are small, simple eyes located between or above the antennae & compound eyes 1-3 in number

15. Head structures A number of different types of antennae are present some are long and of one segment (butterflies) some have may segments (beetles) may also be clubbed (increase in diameter toward apex)

16. Head structures Mouth parts important LABRUM - "upper lip"; broad & flap-like MANDIBLES - heavily sclerotized, commonly tooth-like and nonsegmented- mostly for chewing- modified in some, long & skinny (true bugs) MAXILLAE - pseudotooth-like, segmented- include extentions, palps- modified by some to be long & tubular = stylets LABIUM - "lower lips"; broad, flap-like HYPOPHARYNX - tongue-like structure

18. Head structures In most cases all the head plates are fused into one structure- can see divisions as sutures Essentially all insects have one pair antennae- variation important in taxonomy: a) number segments b) overall length relative to heard size c) presence of a capitate apex

19. Antennae

21. Body Plates Three distinct positions: tergum – upper, dorsal pleuron – lateral sternum – lower, ventral

22. Thorax Three segments, a pair of legs on each- prothorax: 1st pair legs (no wings)- mesothorax: 2nd pair legs + 1st pair wings- metathorax: 3rd pair legs + 2nd pair wings Upper or dorsal surface = pronotum, mesonotum, metanotumcommonly a large segment of metanotum between wings differs = scutellum, commonly will be triangular Openings to tracheal system common on lateral meso- & metathorax (called spiracles)

24. Wings Have either one or two pair- Are outgrowths of the body cavity- Many wings are membranous and have a venation pattern Wing movement produced by change in thorax shape Very important in identification of insects

25. Wings Number of veins present (anterior to posterior)Costa (C) - along leading edge of wingsSubcosta (Sc)Radius (R) - commonly branched, R1, R2, etc.Median (M) - almost always branched once anterior (MA), posterior (MP)Cubitalplical(CuP) - Plical (Pl) and Vannals (V) - some groups these as the Anals (A)

26. Wings Veins connecting between the main veins are the cross veins These have names in some groups, as lower case letters- humeral (h)-radial (r)- sectorial(s)- radio-medial (r-m)- bmedial(m)- medio-cubital(m-cu) The number of cross veins varies greatly- dragonflies (Odonata) with many

27. Wings

28. Legs All have the following (from base to apex) Coxa (coxae) - typically small Trochanter - typically small Femur (femora) - typically the longer Tibia (tibiae) - typically the longertip commonly has a spur(tympanum of crickets & some grasshoppers) Tarsus (tarsi) - commonly with 3-5 tarsomeres (lobes or parts)- the last typically has the claw(s)- also with a pad = pulvillus

30. Legs Much variation present in size & shape of segments Commonly may see:- spines: rigid bristles- setae: flexible hairs

31. Abdomen Of eleven segmentstypically only 7-8 visible1st obscured by thoraxlast modified for reproductive functions Many have tympanum on the first abdomenal segment (hearing) Spiracles commonly quite visible on the pleuron Some Orders with posterior cerci (pair - ex. Orthoptera) or caudal filament (one)some with all three (the silverfish, Thysanura) Reproductive structures may be quit evidentfemales with ovipositor and/or clapser

33. Morphological Variation A number of variations in morphology may make identification hard Upon death changes occur- drying causes them to shrink- alcohol causes them to expand General color variation from one location to another

34. Morphological Variation Immature forms of primitive orders will have shorter wings, etc. Newly emerged adults may have disproportionate 1) size ratios2) colors Difference may also be due to sexual dimorphism