Parent bug
| Parent bug | |
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| Adult Parent bug | |
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| Parent bug with eggs | |
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| Species: | E. grisea
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| Binomial name | |
| Elasmucha grisea | |
Description
The parent bug (Elasmucha grisea) is a common representative of Elasmucha bugs species in Europe.[1] These shield bugs belong to superfamily Pentatomoidea of true bugs, characterized by its shield-shaped body and extended scutellum. The parent bug is a medium-sized bug (7–9 mm in length, males are slightly smaller than females), reddish shield bug with a black and white connexivum. It has an obvious black patch on the base of scutellum , that gets paler towards the tip. They have glands in their thorax between the first and second pair of legs, that are greenish in color, which produce a foul smelling liquid. This liquid is used defensively to deter potential predators and is sometimes released when the bugs are handled carelessly. The antennae are with 5 segments, that get darker towards the end from pale base. When they group in large numbers, they can become significant pests,though they are regulated. [2] [3] [4]
Life cycle
Parent bug males and females overwinter as adults. In spring shortly after copulating males will die. Where as, females will live a bit longer and take care of the eggs and of the juveniles. A female lays a clutch of eggs on leaves of alder and birch trees and stays over the eggs, protecting them until the larvae hatches out. New adults may be observed from August. Like most shield bugs,they feed on plant sap. If two generations occur during the year, the first generation invariably feed on birch, the second on alder. Parent bug needs symbiotic bacteria for the digestion of the sap. They acquire this aid-to-digestion at an early age, their mother smears her eggs with the bacteria so that the young nymphs ingest them as they feed on the egg case. Females of the Elasmucha grisea L. defend eggs and small nymphs against predators. It has been proven that an ecological factor (predation) limits clutch size of this species and the parent bug lays an optimal clutch size as determined by the defending ability of the female. As experimental studies have shown the entire offspring is usually lost to predators such as bugs, beetles, earwigs and ants if there is no maternal protection. Thus, it is safe to conclude that predation is the main mortality factor affecting offspring numbers of this species.[5][6][7]
Ethology
The common name of parent bug, comes from unusual ,relatively rare behaviour in the insect world, protecting and taking care of eggs and young instars called “parental care”. Females lay their eggs only after feeding on host plants with fruit, during the night. Then she stands over the egg batch and shields it throughout egg development. First instars barely moves after hatching, keeping in a compact group with the female, just sucking on their empty egg shells. When first instar nymph tries to leave the aggregation the female tilts her body, stretches with her left antenna to reach the nymph and pushes the nymph back to the aggregation. The second instar moves towards food - catkins - with the female in close attendance. Female keeps a lookout on the larvae constantly and manage them with touches of her antennae. During the third instar, larvae moves towards food and back to the leaf while the female is guarding them. Larvae splits into smaller groups and disperses at the end of the third instar, at which point the female leaves them.[8][6]
It has been noted that in early nymphal instar stages the synchronity of development can become lost. While some nymphs are still in the first instar stage, others already hatched to second instar nymphs and leaves the brood leaf for food and returns. Then female then no longer is able to provide an effective shelter for all her nymphs. Nymphs of different females contact and form mixed groups. In such cases, both single and joint guarding females perform guarding behaviour regardless of whether the nymphs are hers or another female’s offspring. So far, joint brood guarding has been studied in terms of predation defence behaviour. It is assumed that maintaining a „kindergarten“, i.e. a female guarding a mixed group of nymphs, could be an additional factor that promotes joint brood guarding behaviour in E. grisea. Nymphs are likely to benefit from such behaviour, in particular when females disappear or die. [6]
The specialist endoparasite, Subclytia rotundivertis, exploits the parent bug. The parasite injects a single egg through the upper prothorax of female bugs and after hatching the larval parasites eat their host. Parasitism affects, only slightly, a female's ability to defend her brood when the nymphs were at the second instar stage. However, with third-instar nymphs, parasitized females responded markedly less to disturbance at all levels of their defensive behaviour. Parasitism reduces female survival and significantly increases the probability of death before the end of maternal care. Thus, the main cost of parasitism to Elasmucha females seems to be a reduced period of maternal care of the nymphs.[9]
See also
References
- ^ Fauna Europaea
- ^ The Pherobase
- ^ The Wildlife Trusts
- ^ André Bon; E.grisea
- ^ http://beheco.oxfordjournals.org/content/13/6/742.full Phenotypic selection and function of reproductive behavior], Shin-ichi Kudo
- ^ a b c Notes on the bionomics of Elasmucha grisea, S.Roth , W.Adaschkiewitz & C.Fischer
- ^ http://www.royensoc.co.uk/insect_info/what/shield_bugs.htm Royal Entomological Society]
- ^ Evolutionary Ecology, T. Lappalainen, T. Johanna and Tapio Mappes
- ^ Parasites and Female Ability to Defend Offspring in the Parent Bug, Johanna Mappes
External links
- "Species account: Parent bug". British Bugs.
- "Elasmucha grisea L." Nature spot.
- "Observation of Elasmucha grisea L."
- "Experiments with Elasmucha grisea L." by Johanna Mappes and Arja Kaitala.
- "Distribution and Taxonomy".
- "Ovary structure in a presocial insect". by A.Ogorzałek , A.Trochimczuk.