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Encyrtidae

Main diagnostic characters

1. Both sexes with mesopleuron very enlarged, often occupying more than half the thorax in side view (100%)
2. Mid coxae level with middle of mesopleuron in side view (100%)
3. Cercal plates advanced, not at apex of gaster and frequently in anterior two-thirds (99%)
4. Linea calva present and distinct (99%)
5. Mesoscutum transverse and without notauli, or if notauli are present then they are very shallow and curved, never deep and straight (100%)

Included taxa

The family currently includes 460 genera and 3735 species placed in 2 subfamilies as follows: Encyrtinae (353/2920), Tetracneminae (107/815).

Anagyrus pseudococci Gyranusoidea munda
Tetracneminae
(Anagyrus pseudococci)
Tetracneminae
(Gyranusoidea munda)
Leptomastidea abnormis Leptomastix dactylopii
Tetracneminae
(Leptomastidea abnormis)
Tetracneminae
(Leptomastix dactylopii)

Biology

About half of the species of Encyrtidae are associated with scale-insects (Homoptera: Coccoidea), generally as endoparasitoids of immatures or less commonly adults, but with egg predation practised by some species of Microterys (Silvestri, 1919; DeBach, 1939; Sugnojaev, 1984). Almost all species belonging to the Tetracneminae are parasitoids of Pseudococcidae, whilst species of Encyrtinae are known to be parasitoids of a wider variety of coccoids (occasionally also of Pseudococcidae) and other insects, mites, ticks and spiders (Tachikawa, 1981). Among a number of species known to attack psyllids one is a parasitoid of the adults (Robinson, 1961). Many other encyrtids (eg Copidosoma spp.) are polyembryonic parasitoids of larvae of Lepidoptera. Some species are hyperparasitoids via other Encyrtidae, or Aphelinidae, Pteromalidae, Braconidae, Dryinidae, etc.

Tetracnemoidea bicolor
Tetracneminae
(Tetracnemoidea bicolor)
Tetracneminae
(Tetracnemoidea bicolor)
Odiaglyptus biformis Coccidoxenoides perminutus
Tetracneminae
(Odiaglyptus biformis)
Tetracneminae
(Coccidoxenoides perminutus)

The morphology of the egg and first instar larva of encyrtids has been summarized by Maple (1947). The egg is characteristically dumb-bell shaped and is laid inside the host. In many cases the stalk of the egg may remain protruding through the body wall of the host thus enabling the larva, when it hatches, to utilise atmospheric oxygen. The first instar larva is caudate, vesiculate or hymenopteriform (or "encyrtiform") varying from spherical to elongate. The tail may be bifurcate. They vary from 10- to 14-segmented and may or may not have functioning spiracles. Caudate larvae are frequently found in species that parasitize Coccidae. Vesiculate larvae have a caudal vesicle, and may also have a ring of fleshy protuberances around each of the first 12 segments. The so-called encyrtiform larvae are more or less hymenopteriform, but they are metapneustic and remain attached to the egg after eclosion. They are generally 10- or 11-segmented and utilize atmospheric oxygen which they obtain through the protruding remains of the egg-shell (see Askew, 1971: fig. 67). Other immature larvae, with no functional spiracles, absorb oxygen directly through the cuticle. Later instar larvae are more uniform in structure and sometimes enclosed in a sheath which has anastomozed with the tracheal system of the host (eg Encyrtus spp.; Metaphycus spp.) (Embleton, 1904; Alam, 1957; 1959).

Austrochoreia antipodis Anicetus communis
Encyrtinae
(Austrochoreia antipodis)
Encyrtinae
(Anicetus communis)
Cerapterocerus mirabilis Cerchysius sp.
Encyrtinae
(Cerapterocerus mirabilis)
Encyrtinae
(Cerchysius sp.)

Pupation usually takes place inside the body of the host. In some species the host is not killed until after the adult encyrtid emerges. In these species the mature larva makes a pupation chamber in the form of a membranous envelope which becomes confluent with the tracheal system of the host. The envelope then becomes filled with air thus enabling the pupa to respire (Embleton, 1904: Clausen, 1932; Thorpe, 1936). Overwintering is generally as a mature larva or pupa within the body of the host.

Cheiloneurus paralia Comperiella bifasciata
Encyrtinae
(Cheiloneurus paralia)
Encyrtinae
(Comperiella bifasciata)
Diversinervus elegans Encyrtus aurantii
Encyrtinae
(Diversinervus elegans)
Encyrtinae
(Encyrtus aurantii)

Some encyrtids (eg Copidosoma spp.) are of particular interest as they are polyembryonic parasitoids of the larvae of Lepidoptera. Some of these species attack small hosts (eg Holcothorax testaceipes attacking Phyllonorycter spp.) and produce about half a dozen individuals, but others (eg some Copidosoma spp.) that attack large hosts (such as Apamea monoglypha) produce up to two thousand individuals from one parasitoid egg. In many species there are two morphs of larvae, a smaller one which develops normally, and a larger "guard" morph which emerges from the embryonic envelope first but fails to ecdyse and eventually disintegrates (Cruz, 1981). Polyembryonic species often cause the host larvae to become grotesquely deformed and twisted when they are killed as prepupae (see Askew, 1971: fig. 68).

Habrolepis rouxi etanotalia maderensis
Encyrtinae
(Habrolepis rouxi)
Encyrtinae
(Metanotalia maderensis)
Metaphycus stanleyi Microterys sp.
Encyrtinae
(Metaphycus stanleyi)
Encyrtinae
(Microterys sp.)

The Encyrtidae is one of the most important chalcidoid families for the biological control of insect pests (see summary in Noyes & Hayat, 1994). Many species have been used successfully against a variety of economically important pests, especially species of Coccoidea infesting long-lived woody plants. Species which have been particularly successful include: Habrolepis dalmanni introduced from North America into New Zealand for the control of Asterolecanium variolosum, a serious pest of oak; Anagyrus dactylopii introduced into Hawaii from Hong Kong to control Nipaecoccus vastator, a pest of citrus; Tetracnemoidea brevicornis introduced into North America and New Zealand from Australia to control Pseudococcus fragilis, a pest of citrus.

Microterys nietneri Ooenocyrtus gonoceri
Encyrtinae
(Microterys nietneri)
Encyrtinae
(Ooenocyrtus gonoceri)
Pseudectroma signatum Psyllaephagus pulvinatus
Encyrtinae
(Pseudectroma signatum)
Encyrtinae
(Psyllaephagus pulvinatus)

Identification

Peck, Boucek & Hoffer, 1964 (Central European genera); Trjapitzin, 1973; 1978; 1989 (Palaearctic genera and species); Noyes, 1980 (Neotropical genera); Noyes & Hayat, 1984 (Indo-Pacific genera); Prinsloo & Annecke, 1979 (Afrotropical genera).

Syrphophagus cassatus Tachinaephagus zealandicus
Encyrtinae
(Syrphophagus cassatus)
Encyrtinae
(Tachinaephagus zealandicus)

References

Alam, S.M. 1957. The biology of Metaphycus taxi Alam (Encyrtidae: Hymenoptera) in the constant temperature room, with notes on the anatomy of its pre-imaginal stages. Indian Journal of Entomology 19(4):231-240.

Alam, S.M. 1959. The life-history and the larval anatomy of Euaphycus variolosus Alam (Hymenoptera, Encyrtidae) - an endoparasite of Asterolecanium variolosum Ratzb. (Hemiptera, Coccidae). Proceedings of the Zoological Society of Calcutta 12(1):35-40.

Askew, R.R. 1971. Parasitic insects :xvii+316pp. American Elsevier Publishing Co., Inc., New York .

Clausen, C.P. 1932. The biology of Encyrtus infidus Rossi, a parasite of Lecanium kunoensis Kuw. (Hym.). Annals of the Entomological Society of America 25(4):670-687.

Cruz, Y.P. 1981. A sterile defender morph in a polyembryonic hymenopterous parasite. Nature 294:446-447.

DeBach, P. 1939. Microterys titani Gir., an egg predator of Lecanium corni Bouch. Journal of Economic Entomology 32:728.

Embleton, A.L. 1904. On the anatomy and development of Comys infelix Embleton, a hymenopterous parasite of Lecanium hemisphaericum. Transactions of the Linnean Society of London (2) 9:231-254.

Maple, J.D. 1947. The eggs and first instar larvae of Encyrtidae and their morphological adaptations for respiration. University of California Publications in Entomology 8(2):25-117.

Noyes, J.S. 1980. A review of the genera of Neotropical Encyrtidae (Hymenoptera: Chalcidoidea). Bulletin of the British Museum (Natural History) (Entomology) 41:107-253.

Noyes, J.S. & Hayat, M. 1984. A review of the genera of Indo-Pacific Encyrtidae (Hymenoptera: Chalcidoidea). Bulletin of the British Museum (Natural History) (Entomology) 48:131-395.

Noyes, J.S. & Hayat, M. 1994. Oriental mealybug parasitoids of the Anagyrini (Hymenoptera: Encyrtidae) viii+554pp. CAB International, Wallingford, UK.

Prinsloo, G.L. & Annecke, D.P. 1979. A key to the genera of Encyrtidae from the Ethiopian region, with descripitions of three new genera (Hymenoptera: Chalcidoidea). Journal of the Entomological Society of Southern Africa 42(2):349-382.

Peck, O., Boucek, Z. & Hoffer, A. 1964. Keys to the Chalcidoidea of Czechoslovakia (Insecta: Hymenoptera). Memoirs of the Entomological Society of Canada No 34:170pp, 289 figs.

Robinson, D.M. 1961. The parasites of Psyllidae - 2. Parapsyllaephagus adulticollis gen. et sp.nov., the first hymenopterous parasites of an adult psyllid (Homoptera). Ann. Mag. Nat. Hist. (13) 4:117-121.

Silvestri, F. 1919. Contribuzioni all conoscenza degli insetti dannosi e dei loro simbionti. V. La cocciniglia del nocciuolo (Eulecanium coryli L.). Belletino del Laboratorio di Zoologie General e Agraria della R. Scuola Superior d'Agricoltura 13:127-191.

Sugonjaev, E.S. 1984. Chalcid (Hymenoptera, Chalcidoidea) parasites of coccids (Homoptera, Coccoidea) in the fauna of the USSR. Trudy Zool. Inst. Akad. Nauk SSR 117:233pp. (In Russian)

Tachikawa, T. 1981. Hosts of encyrtid genera in the World (Hymenoptera: Chalcidoidea). Memoirs of the College of Agriculture, Ehime University 25(2):85-110.

Thorpe, W.H. 1936. On a new type of respiratory interrelation between an insect (chalcid parasite) and its host (Coccidae). Parasitology 28(4):517-540.

Trjapitzin, V.A. 1973. The classification of the family Encyrtidae (Hymenoptera, Chalcidoidea). Part 1. Survey of the systems of classification. The subfamily Tetracneminae Howard, 1892. Entomologicheskoe Obozrenie 52(1):163-175. (In Russian; English translation: 1975: Entomological Review, Washington 52:118-125)

Trjapitzin, V.A. 1978. Hymenoptera II. Chalcidoidea 7. Encyrtidae. Opredeliteli Nasekomykh Evropeyskoy Chasti SSR 3:236-328. (Ed.: Medvedev, G.S.) (In Russian)

Trjapitzin, V.A. 1989. Parasitic Hymenoptera of the Fam. Encyrtidae of Palaearctics. Opredeliteli po faune SSSR Izdavaemie Zoologicheskim Institutom AN SSSR 158:1-489. Leningrad, Nauka. (In Russian).

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Last updated 07-Jun-2004 Dr B R Pitkin