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42 Cards in this Set

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Describe the differences between mites and insects in their basic body organization.
Unlike insects, which have head, thorax, and abdomen, the Acari have only 2 segments- the gnathosoma (pair of chelicerae and pair of palps) and the idiosoma (the rest of the body including the region with the legs. There is no "head." No antennae although the first pair of legs often antennae-like. Four pairs of legs except in family Eriophyidae which has 2. No wings. Condensed systems. Chelicerae instead of mandibles.
List the major taxonomic categories for mites.
Phylum Arthropoda
Subphylum Chelicerata
Class Arachnida
Subclass Acari (Acarina)
Order Parasitiformes (contains Phytoseiidae and ticks)
Suborder Gamasida (Mesostigmata)- Phytoseiidae
Suborder Ixodida (Metastigmata) - ticks
Order Acariformes
Suborder Actinedida (Prostigmata) - Tetranychidae, Eriophyidae, Tarsonemidae, Tydeidae
Suborder Acaridida (Astigmata) - stored product mites
Suborder Oribatida (Cryptostigmata) - soil or beetle mites
Define idiosoma.
The body segment that includes the rest of the body including the region with the legs.
Define podosoma.
The region containing the legs.
Define opisthosoma.
The region behind the legs.
Define gnathosoma.
The segment containing the pair of chelicerae and pair of palps.
Define propodosoma.
The region containing the first 2 pair of legs.
What kind of chelicerae do the different members of Acari have?
Ticks have a specialized hypostome that is a bar bed piercing organ with retrorse teeth. Spider mites have chlicerae that are highly modified and stylet-like. Most have chelate-dentate chelicerae
Why could there be more mite species than insect species?
Mites are smaller and are able to occupy smaller niches than insects. They also rival the insects in the diversity of habitats they colonize such as terresrial, fresh water, oceans, parasitic on plants, vertebrates or invertebrate animals.
What is agricultural acarology?
the study of mites if importance to agriculture
Define peritreme.
also called stigma, which is the opening to the respiratory system
Define hypostome.
barbed piercing organ of ticks
What is a spermatodactyl?
a chelicerae modification that is used for transferring spermatophores to the sperm receptacle of the female.
What are pedipalps?
they are used as sensory appendages and sometimes become modified for grasping food; there are also used for cleaning the chelicerae after feeding.
What is the typical digestive tract of a mite?
it includes the mouth, which opens into a muscular pharynx connected to the stomach or ventriculus by a long esophagus. The esophagus passes through the "brain" of the mite. A hindgut, divided into anterior and posterior regions opens to the exterior either terminally or subterminally. The gut is usually provided with a nuber of paired diverticula. In some mites, a pair of malpighian tubes may open into the hindgut. Paired salivary glands are associated with the alimentary canal.
Excretions from mites come out as what form?
Mites have a more diffult time surviving in the environment than insects. Why? What physiological limitations do mites have compared to insects?
Mites must maintain the water content of their body. Terrestrial species continually lose water that must be replaced and the aquatic species continually gain water that must be eliminated. This is due to mites being much smaller than insects and thus have a higher surface-to-volume ratio than insects.
How is water conserved in mites?
Most terrestrial mites are cryptic and are found primarily in sites where high relative humidity reducing the rate at which water is lost to the air. Water is also conserved by the epicuticle. Coxal glands help maintain water and ionic balance, especially in ticks.
What is a cultural control method for pest grain mites?
dry the grain and store it in a dry environment
Spider mites intake too much fluid so how do they deal with that?
They have a specialized digestive tract, in which the excess fluids are shunted from the esophagus to the hindgut for elimination.
How does the muscles of mites differ from insects?
The number of muscles in mites is reduced as compared to the muscles in insects.
What are the 2 main types of muscles in mites?
- Intrinsic which extend over the joints of leg segments are are flexors.
- Extrinsic muscles are those of the body and consist of dorso-ventral, oblique, rotator and elevator muscles. They originate and insert on the body wall.
What side of the mite do muscles originate and how do they modify the shape of the body?
- located dorsoventral
- modifies the turgor pressure of the body fluids. Hydrostatic pressure causes the extension of the chelicerae, palps and legs.
Describe the respiratory systems of the different mite suborders.
The location of the stigmata vary.
- Astigmata - absorbs gases through skin
- Prostigmata - opening is in front of body
- Cryptostigmata - opening is hidden
- Metastigmata - stigmatal openings on special plates just behind the fourth pair of legs
- Mesostigmata - stigmata opening on the side of the body between the legs on a peritrematal shield
Describe the nervous system of a mite.
The embryonic arachnid nervous system is similar to that of other arthropods and has ganglia in each segment, but the nervous system of mites has become greatly consolidated. It has become condensed into a compact, unsegmented mass. No central nerve cord or ganlia are found in the opisthosoma and nerves arise from this single concentrated mass.
Describe the sensory system of a mite.
Most of the sensory structures on the body and legs of mites are setalike, although some pores are also sensory. Many are tactile, some are chemosensory and some may be involved in detecting relative humidity. All eyes are simple with a cup-shaped retina. Legs and palps contain numerous sensory receptors.
Someone brings you a small arthropod for identification. How do you decide that you have a mite? How might you identify it?
To decide if I had a mite, I would count the number of legs and see if it had two body segments. I would identify it by mounting it to a slide and using a phase-contrast microscope. Setal structure and location could help identify it further.
Describe the circulatory system of a mite.
The circulatory system in the mites is an open system, with the blood bathing the internal organs. The blood is typically colorless and contains numerous blood cells. The blood circulates by the movement of the dorsal-ventral muscles or, sometimes, by a circulatory organ called a "heart."
What is an aedeagus?
male intromittent organ for transfer of sperm to females
What is a hypopus?
a phoretic deutonymphal stage
What is phoresy?
hitching a ride on another organism such as an insect
What is the typical life cycle for a two-spotted spider mite?
egg --> larva --> protonymph --> deutonymph --> adult (male and female)
C/C diapause and quiescence.
Diapause is a genetically determined state of reduced metabolic activity which typically is induced prior to the onset of unfavorable conditions. Temperature and photoperiod determine it. Quiescence, which occurs in direct response to adverse physical conditions, is terminated as soon as favorable conditions return.
How can mites by dispersed?
- walking
- aerial dispersal, involving silking or other specific behaviors
- phoresy
- as aerial plankton, in which they are picked up and blown long distances
What life stage is usually dispersed in two-spotted spider mites and predatory mites and how do they disperse?
adult mated females that have not yet begun to oviposit so they are not yet weighed down by their relatively large eggs.
Spider mites are dispersed by silk strands and predatory mites stand on their hind legs and blown away.
C/C arrhenotoky and thelytoky.
Arrhenotoky is a genetic system where unmated female tetranychids can produce eggs that develop into haploid males. Thelytoky is where unfertilized eggs produce females only.
How does arrhenotoky allow pesticide resistance to develop rapidly?
Because males in the Tetranychidae are haploid, any new mutations are immediately exposed to selection in the male, so if a male is exposed to pesticides and a single copy of resistance gene is present, the resistance gene will be selected for.
What increases the likelihood that a favorable mutation will be selected?
the combination of sib mating and haplo-diploidy leads to a rapid fixation of any new favorable alleles in a population; therefore, haplo-diploid spider mite species can respond rapidly to selection for resistance to pesticides or for the ability to survive on new host plants.
Describe the reproductive system of mites.
Mites have both direct and indirect sperm transfer. Males that transfer sperm directly into the sperm receptacle of the female often have special structures for grasping the females during copulation. Tetranychidae have an aedeagus, while Phytoseiidae have a spermatodactyl.
Indirect sperm transfer involves deposition of a sperm packet (spermatophore) on the substrate by males then the females pick up the spermatophores and place them in their sperm receptacle.
Why do males guard female deutonymphs?
The female produces a sex pheromone that elicits the "guarding" behavior.
What is the mating behavior of T. urticae?
T. urticae males touch the female with his forelegs. Next, the male crawls under her and holds on by clasping her third and fourth pair of legs with his first 2 pair of legs. At the same time, the idiosoma of the male is arched upwards so that the aedeagus is introduced into hte genital opening of the female. At this stage, the female will permit a full coputlation to occur or will terminate the mating.
Describe parahaploidy.
All eggs must be fertilized. Phytoseiid eggs that produce females remain diploid. In males, the diploid eggs undergo development, but about halfway through embryogenesis one half of the chromosomes are heterochromatinized and eliminated from the cells, leaving the male haploid for the rest of his life- having only the females genes.