FEEDING
Ladybirds are beneficial to humans mainly because they eat aphids (greenfly, blackfly etc.), however this applies to only some species. Most ladybirds eat bugs of some sort (there are many types of these other than aphids: coccids, adelgids etc: see Hemiptera) but some eat plants and fungi.
HERBIVORES: plant-eaters: members of the Epilachnini are herbivores (phytophages) and include two British species: the 24-spot (which eats grass, particularly false oat grass, and some other plants) and the Bryony (which eats white bryony and related plants). Some of this group are pests in other parts of the world: such as the Mexican Bean Beetle or even the Bryony which in France is known as the Melon Beetle.
FUNGIVORES: fungus-eaters: At least two British species are essentially fungivores (mycetophages), they eat mildews rather than large toadstools: the 22-spot and the Orange ladybirds. The 16-spot is now thought to be primarily a fungivore.
CARNIVORES: eat other animals. Their
prey is usually homopteran (various bugs) but they will
also eat other invertebrates, especially larvae and are
commonly cannibalistic as larvae.
Predators of aphids:
aphidophages: these include the two most common British
species (the 2-spot and 7-spot) but also the Scarce
7-spot, 10-spot, 11-spot, Adonis', Water, Cream-spot,
14-spot, Striped and Eyed ladybirds. Some species seem to
have only one prey, thus the Heather ladybird was thought
to be limited by availability of the Heather aphid (see
below). Some species are thought to be aphidophages (e.g.
Cream-streaked) but few observations have been made. The
atypical coccinellids Rhyzobius
litura, Coccidula scutellata & C. rufa
(probably most others) are also primarily aphidophages.
Predators of adelgids:
eat the 'woolly aphids' of coniferous trees: Larch
and18-spot. Are also probably a major food-source for
some
Scymnus species.
Predators of coccids:
eat scale insects: the Pine ladybird has adapted to a
large number of scales. The Kidney-spot has a more
limited range. Probably a major food for
Nephus
species.
Predators of beetles:
the Hieroglyphic ladybird can feed on aphids but has been
shown to feed on the eggs and larvae of leaf beetles,
particularly the heather beetle (Lochmaea
suturalis).
Predators of mites:
the Cream-spot, 14-spot, Kidney-spot and Pine have been
observed to eat mites but these are probably only
secondary foods. They seem to be major foods of
Stethorus
punctillum.
GENERALISTS? There are species which are very closely tied to a single prey but most ladybirds will turn to other food if their optimal prey becomes scarce. Other connections may be tenuous: the Heather ladybird eats the appropriate aphid perhaps because nothing else is available and it has been suggested that it can eat various scale insects if these are found. Some species, notably the 16-spot, seem to take a variety of foods: mildew as well as aphids (mites and pollen have also been noted). The Orange and Pine ladybirds have been observed eating aphids. Nectar, pollen and honeydew (the sweet excretion of aphids) may be taken by most species. The 14-spot is perhaps the most versatile feeder.
PRIMARY and SECONDARY food sources.
It is clear that most ladybirds can eat many foods but most of these are secondary. For instance nectar and honeydew are often taken by mature ladybirds (imagines) since they provide sugars (to power flight) and water: they would not provide sufficient nutrition for growth of larvae. They are secondary or supplementary foods. Prey that will provide all of the nutritional requirements for ladybird development is primary or essential. This may not be one particular species: for instance the black bean aphid (Aphis fabae) is more likely to be eaten by ladybirds in urban areas because it is more commonly available than the pea aphid (Acyrthosiphon pisum) although the latter is regarded as an essential prey. Aphids have defensive chemicals which can be harmful to ladybirds: thus the elder aphid (Aphis sambuci) is insufficient for ladybird growth although it is very closely related to the black bean aphid. Most British ladybirds could live on A. pisum or A. fabae but some (Hieroglyphic and Striped) must have other essential prey species (as probably do many of the small, atypical coccinellids: Scymnus auritus, for instance, is thought to prey mainly on the oak aphid Phylloxera glabra).
Therefore don't be surprised to see ladybirds eating strange food items. Let us know of any observations.
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A conundrum? Pine and Kidney-spot ladybirds are primarily consumers of scale insects, yet they are active for parts of the year when there are no scales available. Do they carry enormous stocks of nutrients in their bodies over winter? Several people in our survey have observed that these species seem to nibble at lichens (left) or graze green algae on tree trunks. Are these secondary food sources? |
In their early stages, ladybirds, like lots of other animals will
eat members of their own species: cannibalism.
Created 9/4/02