Entomology 10: Natural History of Insects
Lecture: Jan 8, 1999
Classification, Ancestery, Apterygota, Wings
Slide 1
Classification
- vast array of organisms in nature, especially insects (>1 million)
- as humans we need to name and organize items before we can discuss and conceptualize about them
- examples with wrenches, grocery store items
- we also name, organize, and categorize organisms
Slide 2
A Formalized System of Classification is used
- Taxonomy: science of naming describing and classifying organisms. Taxon (pl. Taxa) is a group of organisms at some taxonomic level
- Phylogeny: study of history of lines of evolution. Phyle = tribe (family lineage). Genesis = origin (both from the Greek)
- Systematics: study of the phylogenetic relationships of organisms.
- - To be useful, classification should be as natural as possible. Group should be derived from a common ancestor. Allows the most predictive framework. Can predict characteristics of new taxa based on existing framework.
Slide 3
Classification uses a hierarchical or nested arrangement of taxa
- Phylum - Arthropoda
- Class - Insecta
- Order - Orthoptera
- Family - Acrididae (always ends in idae)
- Genus - Romalea
- Species - microptera
- many other infracategories, but these are most common
Slide 4
Romalea microptera - eastern lubber grasshopper
- Our place in the the classification scheme of things
- Phylum - Chordata
- Class - Mammalia
- Order - Primates
- Family - Hominidae
- Genus - Homo
- Species - sapiens
- Scientific name: Homo sapiens
- Common name: human being
Slide 5
Carl Linneaus (Carl von Linne) is responsible for the present system of classification
- Zoological nomenclature starts with his publication: 10th edition of Systema Naturae in 1758
- rules of zoological nomenclature were slow to evolve: 1st International rules around 1900
- all species have two names - binomial nomencalture: the genus and species
Slide 6
- Linne developed this to facilitate student field notes
- previously each species had a paragraph long description
- each species needs a unique name: uniform code of rules needed to ensure uniqueness and to resolve conflicts:
- two species have the same name
- one species has >1 name
Common names
- many organism have common names, especially common insects and pests. Honey bee, house fly. Rules exist for common names. If belong to that taxon, then two words. If not one word. Example: House fly and dragonfly
Slide 7
At the international level, common names are that useful -- too variable
Most insects are not that well known to have common names
Latin names are used as universals. Regardless of the language of the publication, when latin names are used, all know what insect is being discussed
Chinese mantids, coconut scale, tropical rat louse, crazy ant,
Carolina grassh., lead cable borer, goat sucking louse, greedy scale,
German cockr., corn leaf aphid, uglynest caterpillar,
Hawaiin carpenter ants, Tahatian coconut weevil, onion maggot, common cattle grub
Slide 8
What is a species? The Biological Species Concept
Species - groups of interbreeding natural populations which are reproductively isolated for other such groups
Not an easy concept to apply. Some insects do not mate and yet produce viable offspring (example include some weevils, bees, wasps do not have any males, reproduce asexually.
In these cases we must deduce reproductive relationships based on taxonomy (morphology), behavior, and ecology.
Slide 9
Another problem: experts do not always agree on common ancestor/phylogeny
- relationships among higher taxa are difficulty to determine
- many entomological texts will differ in their naming of insect orders, families, and genera; splitters vs. lumpers
- what constitutes a species is not always agreed upon
- Species determination:
- morphology/ecology - classical
- behavior (acoustic)- sibling species
- genetics (allozymes) - allele frequencies
- DNA (nuclear/mitochondrial)
Slide 10
Where did insects come from? What is their origin?
- highly speculative. Ancestor was probably a type of earth worm
- Earth worms:
- reproductive organs located at the anterior end
- insect reproductive organs located at posterior
- both are segmented
- Hypothsis: annelid with reproductive tract near tail
- development of legs on each segment plus pair of antennae on the head
- Legs were jointed, 1st 4 segments fused with the head, next 3 became the thorax
Slide 11
Where did insects come from? What is their origin?
Hypothesis:
- progressive fusion of segments and differentiation of head (mouthparts) and thorax
- reduction of legs on the abdomen, except at the tail end
- loss of abdominal legs, complete differentiation of head thorax, and abdomen. Only 3 pairs of legs
- Living Fossil = Peripatus (3rd floor Briggs Hall)
- soft bodied, segmented appendages, body segmented
- has insect like mandibles
Slide 12
Did insects evolve from one ancestor or more?
Monophylectic - having one common ancestor (some insects)
Polyphylectic - having more than one ancestor (arthropoda
Fossil record is not that good.
The basic divisions of the Insecta:
Apterygota vs. Pterygota
"A" = without: Pterygion = wings
Apterygota without wings; never evolved them and radiated before wings developed
Four orders: Protura, Collembola, Diplurans, Thysanura
Slide 13
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Slide 16
Pterygote insects dominate:
Evolution of wings one of the most important adaptations arrived at by insects
- ancestral dominance
- escape from predators
- find new habitats (food)
Evolution of wings in birds, bats and flying mammals is easy to trace; modified forelimbs
Insects have retained their legs, and yet have wings
Slide 17
What strutures gave rise to wings and what was (were) the original function(s) of these structures?
- wings were new structures derived at the junction of the top (notum) and sides (pleura) of an insect
- attitude adjustment when falling (hit the ground running)
- gliding between high points (flying squirrels)
- lobes became differentiated to function at wings
- Types of wings:
- fixed vs. flexed (folded)
- (dragonflies, mayflies vs. all others)
- no wings vs. secondary loss of wings
- silverfish vs. lice, fleas, etc.
Slide 18
Insects can fly very well. How do you think flies got their name?
How Fast? How Far?
Wing Beat Frequency?
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