Synonyms and other taxonomic changes
Taxonomy on BG follows(1)
1351 spp. in 224 genera (w/40 subgenera) in our area, of which ~80 spp. are pests of food crops and ornamental plants(2)
and almost 300 spp. are adventive(3)(4)
Overview of our fauna (* –taxa not yet in the guide):Family APHIDIDAE
Aphids are generally small insects ranging from ~1-6mm in body length.
Most aphids can be identified to family level by two tubelike projections on the posterior, called cornicles or siphunculi
, although in some exceptions the cornicles are greatly reduced or absent. The cornicles emit pheromones to alert other aphids in the colony when danger, such as a predator, is nearby. They also offer mechanical protection, as the fluid emitted can gum up the mouthparts of the predators.
Species identification often requires specific views of the specimen, and many cannot be reliably identified with images. Aphids are often difficult to identify with a well place slide mount and a high powered scope due to their small size and often minor differences in characters used in identification. For example, two species may be separated by the shape and number of secondary sensoria on antennal segment three. When submitting images of aphids, more angles and views increase the likelihood of identification. Alate forms are often easier to ID than apterous, and some forms such as oviparae are poorly known so they usually can't be identified beyond family. Immature aphids generally cannot be reliably identified either.
Species identification is usually easier if host plant is known, but similar aphid species may infest the same host. An attempt to organize aphid images by host plant
Guides covering global fauna: aphids on trees (5)
• crops (6)
• herbaceous plants & shrubs (7)
• combined (8)
(emphasis on European genera)
mostly temperate zone of the Northern Hemisphere
Different species have what are called peak flights during the growing season. Males are usually observed in the fall, and different morphs can also be present at specific times.
Aphids suck juices from plants and may be quite damaging. Some are restricted to a single plant species or group of related plants. Others may alternate between two entirely unrelated host plants as a necessary part of their life cycle (e.g. Dysaphis plantaginea
begins the year on apple, then migrates to narrow-leaved plantain for several generations before winged adults return to apple trees where they produce eggs that will overwinter). Aphids that do alternate host plants are called heteroecious, and those that do not host alternate are known as monoecious. Aphids that feed on multiple species of plant are known as polyphagous, a few different plants in oligophagous, and if they only utilize one species of plant they are monophagous.
Aphids can follow two types of life cycle, holocyclic and anholocyclic. Holocyclic species alternate between sexual and parthenogenetic reproduction. Over-wintering eggs produced by sexual reproduction hatch in the spring into wingless females. These wingless females are known as fundatrices, are parthenogenetic
(able to reproduce without fertilization) and hold embryos in their bodies to give birth to live young (known as viviparae). As the colony grows winged females known as alatae may be produced, although they are unknown in some species. Near autumn as the photoperiod shortens and temperature decreases, male forms and egg-laying females (oviparae) are produced. After mating, the oviparae lay fertilized eggs which overwinter. In anholocyclic species there is no sexual reproduction, only parthenogenetic repoduction. This is especially common in warm climates where overwintering is unnecessary. There are some anholocyclic species, such as Aphis nerii
, where males have never been observed in the wild in North America.
Feeding aphids excrete a sugar-rich liquid known as honeydew, often consumed by ants who are known to tend aphid colonies and protect them from predators in exchange. Ants are herding aphids and "milk" them by stroking. Some ant species move aphids from one plant to another when the food supply is insufficient, or even take aphid eggs into their nests to help them overwinter.
Predators of aphids include (left to right, below) lacewing larvae, ladybird beetles and larvae, harvester butterfly caterpillars, and syrphid fly larvae.
Aphids are also attacked by parasitic wasps, which lay eggs inside them. Parasitized aphids swell, become lighter in color and are eventually killed by the developing wasp inside. These are referred to as "aphid mummies."