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Aphid Predator (Hemiptera: Anthocoridae)Anthocoris nemorumCommon flower bug, Minute pirate bugOn this page: Identification & Distribution Biological Control of Aphids Predation of foxglove aphid Predation of willow aphid Intraguild predation Man-bitingIdentification & DistributionAnthocorid bugs have soft elongated flat bodies, often patterned in brown, black and white. The various species of the genus Anthocoris can be difficult to tell apart. Adult Anthocoris nemorum (see first two pictures below) are 3-4 mm in length. Antennal segments I and IV are usually dark, whilst segments II and III are mainly pale with dark apices (cf. Anthocoris nemoralis and Anthocoris confusus which have only antennal segment II pale at the base). The Anthocoris nemorum pronotum is black and the forewings are entirely reflective (this does not always show in photos). There is a dark patch on the wing membrane which is typically shaped like an hourglass. The legs are orange-brown often with a dark patch at the proximal end of each tibia, and a dark patch on each femur, especially on the hind legs.
Immature Anthocoris nemorum are brown or reddish brown - the third picture above shows an immature anthocorid. Anthocoris nemorum is mainly found on low vegetation rather than trees, and is especially common on nettles (cf. Anthocoris nemoralis and Anthocoris confusus which are mainly found on trees). Anthocoris nemorum is an voracious predator of aphids and other small insects, and has been considered as a potential agent for biological control of aphids, for example of the damson-hop aphid (Phorodon humuli) and of the pear psyllid (Cacopsylla pyri). Anthocorids may also suck plant juices, but they cannot grow or reproduce on a purely plant diet. The species has a wide distribution stretching from Europe right across the Palearctic zone to China. Biological Control of AphidsAnthocoris nemorum is a highly polyphagous predator having been recorded feeding on 35 different arthropod prey in 20 families of insects and 5 mite families on 17 different plant species (Hill, 1957). More prey species have since been recorded. The species is known to be important in the natural biological control of a number of aphid species including pest species. For example Campbell (1977) found that Anthocoris nemorum, and Anthocoris nemoralis were the most abundant aphidophagous insects consuming hop aphids on hops. Subsequently Cranham (1982) noted that, following an early season soil drench of insecticide, insect predators particularly Anthocoris nemoralis and Anthocoris nemorum usually contribute greatly to the integrated control of Phorodon humuli for the remainder of the season, providing harmful insecticides are not used. Despite its ubiquitous nature in natural ecosystems, the species has been rather little used in either classical biological control programmes or for augmentative release. Herard & Chen (1985) evaluated the potential effectiveness of Anthocoris nemorum for biological control of pear psyllid (Cacopsylla pyri). Anthocorids were then collected in France and sent to the western United States (Herard, 1986), but the species did not become established. Some years later Sigsgaard et al. (2006) carried out experimental releases of both Anthocoris nemorum and Anthocoris nemoralis against pear psyllid. They were shown to bring about considerable reductions in pest numbers. We give below some examples of aphid predation by Anthocoris nemorum that we have recorded. Predation of foxglove aphidThe common flower bug is best known as a predator on low level vegetation such as on foxgloves (Digitalis purpurea). All development stages of Anthocoris nemorum are predatory - the picture below shows a fourth instar nymph predating aphids on foxgloves.
It's prey in this case was most likely the foxglove aphid (Aphis armata) given the photo was taken in early June, which is rather too early for large colonies of the migrant Aphis fabae to have built up. Predation of willow aphidsAlthough Anthocoris nemorum is best known as a low-level vegetation predator, it can also be found on trees such as on the willow below.
Here it is feeding on one of the Cavariella species, most of which use Salix as the primary host. Intraguild predationIntraguild predation is defined as the killing and sometimes eating of potential competitors. The image below shows an example of intraguild predation, namely an adult Anthocoris nemorum consuming a mummified aphid on foxglove. The mummy contains the pupa of an aphid parasitoid, probably an Aphidius species.
Mehling et al. 2004 investigated the magnitude of intraguild predation by adult females of the predator Anthocoris nemorum on immature larvae of the aphid parasitoid Aphidius colemani inside mummies of peach-potato aphids Myzus persicae in a preference experiment. Each predator consumed a mean of 2.8 immature parasitoids within mummies and 3.6 unparasitized aphid nymphs. It did not appear to exhibit prey preference between mummies and unparasitized aphids. The impact of intraguild predation on the efficacy of biological control of the prey can be difficult to predict, but is generally considered to be detrimental to the level of control. Man bitingBoth adult and immature anthocorids have frequently been recorded biting man. Smith (1990) describes how bites left a tiny red puncture, which however only lasted a few hours. Verdcourt (1990), however, reported that the resulting red marks persisted and itched for 2 or 3 days. Atkinson (1990) noted that the insect generally flies away immediately after biting.
The anthocorids in the pictures above were certainly very ready to bite, but there was no indication that they were sucking up any fluids after biting. We concluded they were simply probing to assess the suitability of the potential 'prey' - having discovered its unsuitability, it would not be surpising if the anthocorid departed.
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