Aphids, also known as plant lice, are small sap
sucking insects, and members of the superfamily
Aphidoidea in the order Hemiptera with worldwide
distribution. They are among the most important
group of insects that considered as serious pests on
cultivated plants in temperate regions. So far more
than 4400 aphid species have been identified in the
world which are increasing in number day by day.

Aphids: life cycle, reproduction, morphs and
   Aphids are small (1-10 mm in length), soft-
bodied insects which feed on the phloem of their host plants
using piercing stylets as mouthparts [1]. These insects
exhibit a various range of relatively complicated life cycles.
Each has a number of different stages and for each stage
there is one or even more specialist morphs. These morphs
are adapted for specific purposes in the life cycle [2]. They
breed predominantly by apomictic parthenogenesis whereby
largely genetically identical offspring  are produced
mitotically involving a process of “telescoping of
generations” [see 3,4].
The life cycles of aphids can be divided into two
types based on how they utilize their host plant: 1) Non
host-alternating life cycle (monoecious or autoecious) in
which the aphids feed and reproduce on either one host
plant or some closely related plants during the year. They
can produce eggs on the same group of host plants that is
fed on by all of the parthenogenetic generations. 2) Host-
alternating life cycle (heteroecious) in which aphids have
two distinct types of host plants i.e. primary host plants
which are mostly woody (e.g. Rosaceae) and secondary
host plants which are herbaceous. In species which retain
an autumnal sexual phase, following mating of the sexual
morphs, overwintering is achieved as cold-hardy eggs on
the primary host, whilst in the following spring and summer,
winged asexual females are produced and migrate back to
the secondary host where they produce numerous
parthenogenetic generations. In the autumn, winged forms
(males and pre-sexual females or gynoparae) are produced
within the asexual lineages as a result of the short day
length and low temperature conditions, and migrate back to
the primary host and lay eggs to complete (and in effect re-
set, i.e. cyclical parthenogenesis) the life cycle [2,3,5,6].
In the terms of producing eggs in aphids, there
are two types of life cycles. Some aphid species are
holocyclic, meaning that they produce eggs in their annual
life cycles, but some other never produce egg and
overwinter as asexual females (virginoparae) or their
nymphs; this group are described as being anholocyclic. In
between, there are some aphid species that show both
holocycly and anholocycly [2,3]. In species with a sexual
phase, at the beginning of the spring, the first morph to
hatch from overwintering eggs is termed fundatrix (first
asexual females (i.e. initial asexual lineage stem mothers));
these begin to reproduce by parthenogenesis and give birth
to other parthenogenetic females that establish several
generations during the year. An aphid’s lifespan within an
asexual lineage is generally short and within a few days
(usually 7-10 days) they thus soon become adults [3,5].
In aphids, various types of morphs occur in
relation to biological characters in their life cycle. There
could be five or even more different adult female phenotypes
in the life cycle of an aphid lineage, distinguished in
connection with heterogony and host alternation. Different
morphs are specialized for different tasks such as
reproduction, dispersal, and surviving severe or less
favorable climatic or nutritional conditions [5,7]. One of the
most common morphs in aphids is winged morph, which is
specialized for dispersal. The two main advantages of
producing winged dispersal morphs in aphids are
migration and dispersal between different host plants, and
escape from adverse environmental conditions [3,5]. In a
metapopulation setting, dispersal is even more important as
each plant is an island of resource separated by unsuitable
habitat that the aphids have to navigate before reaching the
next suitable plant.

1. Miyazaki M (1987) Morphology of aphids. In: Minks AK,
Harrewijn P, editors. Aphids, their biology,
natural enemies and control Amsterdam:
Elsevier. pp. 1-25.
2. Williams IS, Dixon AFG (2007) Life cycles and
polymorphism. In: van Emden HF,
Harrington R, editors. Aphids as Crop
Pests. Wallingford: CAB International. pp.
3. Dixon AFG (1998) Aphid Ecology: An optimization
approach. London: Chapman & Hall. 300 p.
4. Blackman RL (1987) Reproduction, cytogenetics and
development. In: Minks AK, Harrewijn P,
editors. Aphids, their biology, natural
enemies and control Amsterdam: Elsevier.
pp. 163-195.
5. Kawada K (1987) Polymorphism and morph
determination In: Minks AK, Harrewijn P,
editors. Aphids, their biology, natural
enemies and control Amsterdam: Elsevier.
pp. 255-266.
6. Blackman RL, Eastop VF (2000) Aphids on the world's
crops (An identification and information
guide). London, UK: John Wiley & Sons.
7. Miyazaki M (1987) Forms and morphs of aphids. In:
Minks AK, Harrewijn P, editors. Aphids, their
biology, natural enemies and control
Amsterdam: Elsevier. pp. 27-50.
  Mehrparvar Laboratory
Aphidology Research Group
Graduate University of Advanced Technology             Institute of Science and High Technology and Environmental Sciences
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You can learn more about aphids by clicking on the below links:

Aphids on the World's Plants

Aphid Wikipedia

Aphid Species File

Aphid Net

Aphid Identification
(Characteristics of genera)