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Aphid
Aphids and ladybug

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Acyrthosiphon pisum, pea aphid

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cellular organisms - Eukaryota - Fungi/Metazoa group - Metazoa - Eumetazoa - Bilateria - Coelomata - Protostomia - Panarthropoda - Arthropoda - Mandibulata - Pancrustacea - Hexapoda - Insecta - Dicondylia - Pterygota - Neoptera - Paraneoptera - Hemiptera - Sternorrhyncha - Aphidiformes - Aphidomorpha - Aphidoidea - Aphididae - Aphidinae - Macrosiphini - Acyrthosiphon - Acyrthosiphon pisum

Brief facts: aphids (Aphididae)

Brief facts: pea aphid (Acyrthosiphon pisum)

Aphid life cycle

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Developmental stages

Most aphids have two genetically distinct types of life cycle within the one species: holocyclic and anholocyclic. In the holocyclic life cycle, multiple generations reproduce asexually from spring through to summer and to early autumn and then, in response to decreasing photoperiod, sexual morphs (males and egg-laying females – the oviparae) are produced, which mate and lay the overwintering eggs, which are very cold hardy. Anholocyclic clones arise from a genetically stable mutation that renders the aphids unresponsive to the decreasing photoperiodic cue that triggers the sexual morphs and egg production in the autumn. These clones reproduce asexually the whole year round, with increases and decreases in the rates of development and reproduction governed by seasonal changes in temperature. However, in contrast to their eggs, the overwintering ‘active stages’ of anholocyclic clones are much less cold hardy – mortality increases from 0% to >90% as the temperature decreases from around –5°C to <–15°C.

Life Cycle Stages

The holocyclic life cycle of the pea aphid begins at spring and continues up to the moment when the insects start laying eggs for overwintering. In warm climates adult insects can continue feeding and parthenogenetic reproduction even in winter months.

Lacking larval and pupal stages aphid's metamorphosis is incomplete.

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Effect of climate change on aphids

Aphids preferentially inhabit temperate regions of northern hemisphere. They are particularly well adapted to regions with cold winter because their eggs are very cold hardy. The rate of development in aphids is directly dependent on temperature. The minimum tempereature at which development of A. pisum can proceed ranges between 2.3 and 6.3 °C. A female aphid requires a certain number of degree-days above the threshold to reach adulthood (99-147 in A. pisum). This is a particularly short generation time even among insects. In some european countries aphids are mostly living in suboptimal temperature conditions. Therefore, global warming would favor the proliferation of aphids. For example, an increase in temperature of only 2°C would allow the number of generations produced per year to increase from 18 to 23 in the UK.

Other biological functions influenced by temperature include dispersal and reproduction. Higher temperatures increase both the number of winged individuals produced and their flying capacity. Lower temperature thresholds for flight are generally around 13-16°C and upper thresholds around 31°C.

Sustained temperatures above 20°C might delay or even totally prevent sexual reproduction in aphids thus allowing parthenogenetic reproduction and the survival of active individuals throughout the year.

Aphids are also affected by environment through the host plants. Increases in CO2 and O3 that affect plants negatively elicit varied responses depending on aphid species and it is not possible to establish general rules for all aphid populations.

At a pan-European scale, the EXAMINE observation network has provided evidence for an increase in the number of aphid species present over the last 30 years and for earlier spring flights.

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References

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