Checklist of UK Eupelmidae (Walker 1846)

Description & Statistics

Eupelmidae is a moderately sized family with circa 59 valid genera and 712 species known as of 1993. Although cosmopolitan, the family is most abundant in the tropics.

Important morphological characters include antenna with a single annulus; mesoscutum of female impressed, at least posteriorly; mesopleural area convex; middle tibial spur long and wide. The body is often metallic colored, and forewings when present have a long marginal vein. The fore and hind coxae are widely separated.

The family has diverse habits and biologies. Most species are primary, solitary parasitoids, although some are hyperparasitic. Both ecto- and endoparasitic species are common. Some species are facultative hyperparasitoids; these species are internal parasitoids when primary and ectoparasitoids when secondary. Generally, the family exhibits a wide host range. They are principally egg parasitoids or larval and pupal parasitodis of Hymenoptera and Diptera that feed on graminaceous plants. Some species are good jumpers. Eupelmidae have found little use in biological control, with only a few species having been introduced into various countries as biological control agents.

The family is quite common, with the most frequently encountered genera being Anastatus and Eupelmus. Clausen (1940) noted that Anastatus is essentially primary in its host relationships, and the various species attack eggs of Orthoptera, Hemiptera and Lepidoptera. All egg-attacking species, with exception of A. amelophagus that is predaceous on Ameles eggs, are solitary and endophagous. Infrequently they are also found as solitary external parasitoids in dipterous puparia, in particular those of Tachinidae and Cecidomyiidae. An exception is found in Anastatus viridiceps Waterst. where 15 individuals have been found to develop in a single tsetse fly puparium (Clausen 1940/62).

There is a great diversity in habit, as shown in the genus Eupelmus. Some species are primary external parasitoids, others are obligatory hyperparasitoids, and quite a few are both primary and hyperparasitic. Eupelmus cicadae Gir., E. excavatus Dalm., Arachnophaga picea How. and Lecanobius cockerelli Ashm. are egg predators. A. picea is predatory in spider egg sacs even though it has been reared from Chrysopa. E. popa Gir. is predaceous on larvae and pupae of Contarinia. Clausen (1940) noted that various species were external parasitoids on the larvae of phytophagous Chalcidoidea. Eupelmella vesicularis Ratz. (= Eupelminus saltator Lind.) is external on the larva or pupa of the hessian fly within the puparium when it develops as a primary. Calosota sinensis Ferr. is gregarious and external on mature larvae of Pareumenes.

Host preferences are wide, as shown in Eupelmus urozonus Dalm. This species is externally parasitic on the larva of the olive fly, Dacus oleae Rossi in Italy, but it has also been reared as a hyperparasitoid of that same host and from various other Hymenoptera, Coleoptera, Diptera, Hemiptera and Lepidoptera (Silvestri et al. 1908).

A large number of eupelmid species that are normal primary parasitoids also have been found to develop as hyperparasitoids on primary parasitoids that are not associated with the normal host. Anastatus disparis Ruschka, parasitic on gypsy moth eggs, has been found as an external parasitoid of the larvae of Apanteles in the cocoons., and Anastatus pearsalli Ashm., which usually attacks eggs of Lepidoptera, has also been reared from Apanteles. E. spongipartus Foerst, which is mostly parasitic on Cynipoidea, and Eupelmella vesicularis, that is a primary parasitoid of the hessian fly, both have been reared many times from Apanteles melanoscelus Ratz. (Muesebeck & Dohanian 1927). Eupelmus tachardiae How. is believed to be a solitary internal parasitoid of the lac insect, Laccifer lacca Kerr in India, but it also develops as an external parasitoid on Microbracon greeni Ashm., that is a parasitoid of a lepidopterous predator of the same scale insect (Glover et al. 1936).

A large number of Eupelmidae are able to develop consistently as internal parasitoids of their principal hosts and as external parasitoids when behaving as hyperparasitoids. This adaptation is uncommon among insect parasitoids and Clausen (1940) thought its significance was not clear. This behavior is different from the case of Coccophagus where there is a differential development of the sexes, because both sexes are produced on the same host when development is internal.

Anastatus disparis, was introduced into the United States from Japan and Europe in 1908-09 for the biological control of gypsy moth. Another species, A. semiflavidus Gaham, has been tested on a large scale in New Mexico, its native habitat, for control of the range caterpillar, Hemileuca oliviae Ckll (Clausen 1940/62).

Specific Geographic Areas

NEARCTIC (CANADA).-- Yoshimoto (1984) noted that "The family Eupelmidae is composed of three subfamilies: Calosotinae, Eupelminae and Tanaostigmatinae. The Tanaostigmatinae is a southern group and does not occur in Canada. The members of this group can be distinguished from other eupelmids by having two anelli and entire notauli that converge and merge medially before reaching the posterior margin of the mesoscutum."

"The members of this family are characteristically elongate and commonly metallic in color; they resemble Encyrtidae in having an enlarged inflated mesopleuron (at least in females) and in having an elongate and stout mid tibial spur. Riek (1970) placed the eupelmids and aphelinids as subfamilies within the Encyrtidae. Burks in Krombein et al (1979) placed the eupelmids as a separate family. Except for males of the subfamily Eupelminae, the eupelmids can be recognized by the following characters: Mesopleura enlarged, inflated, evenly convex and smooth, without impressed lines or grooves; female notauli not distinct or complete (except for the Tanaostigmatinae); mesosternum elongate, with mid coxae situated near hind coxae, posterior to midline of mesopleura. Wings often reduced, in fully winged forms with marginal vein long. Head and gaster arched upward in dead specimens so that body dorsally concave to U-shaped. males of the subfamily Eupelminae do not possess the family characteristics as listed above except for an elongate mid tibial spur. The mesopleuron is divided into a mesepisternum and mesepimeron by a femoral groove, and the notauli are entire. In these characters they closely resemble males of the family Pteromalidae, particularly the subfamily Cleonyminae."

Yoshimoto (1984) provided a key to the subfamilies of Eupelmidae, emphasizing Canadian groups. Subfamileis Calosotinae & Eupelminae are recognized. In Calosotinae, only Calosota Curtis is known from Canada. Of Eupelminae, the genera Anastatus Motschulsky, Arachnophaga Ashmead, Eupelmus Dalman, Metapelma Westwood, and Macroneura Walker are known from Canada.

Calosotinae.

This subfamily was proposed by Bou…ek (1958) who provided a key to genera, synonymy and new name combinations. Bou…ek noted that "The group is distinguished from the subfamily Eupelminae by the following characters: Pronotum entire, distinctly narrower than thorax, with sides subparallel, thus appearing quadrate; mesoscutum semiquadrate, with linear and subparallel notauli in Calosota and with linear and convergent notauli in Eusandalum; axillae reduced, width of medial part of scutellum basally subequal to or greater than width of axilla, and body elongate and slender, as in many Cleonyminae of the family Pteromalidae. There are two genera and 16 species in North America, of which only Calosota Curtis is known from Canada. The genus Eusandalum will probably be found in British Columbia."

The North American species of Calosota Girault (1917) were revised by Burks (1973) who also presented a key to the described species of Eusandalum. Yoshimoto (1984) noted that all known species of Eusandalum are parasitoids on wood-boring beetles (Cerambycidae, Scolytidae). Calosota spp. are either primary or secondary parasitoids of Hymenoptera (Eurytomidae, Torymidae) and Diptera (Cecidomyiidae) in stems of grass.

Eupeliminae.

Yoshimoto (1984) commented that this subfamily is by far the most common and heterogeneous group of Canadian eupelmids. He stated that "There are 10 genera and 77 species (Krombein et al 1979). Merostenus excavatus Dalman was introduced into North America but no specimen has been collected since 1924. The genera Anastatus Motschulsky, Arachnophaga Ashmead, Eupelmus Dalman, Metapelma Westwood, and Macroneura Walker are known from Canada."

Females are distinguished from the Calosotinae by a pronotum that is usually divided medially, not obviously narrower than thorax because its sides converge and do not appear quadrate; a mesoscutum that is longitudinally concave or depressed medially, lacking clearly defined notauli; the axillae are often contiguous but this trait is also found in Calosotinae; Mesopleuron convex. Females of several species have short wings.

Yoshimoto (1984) stated that "The members of Eupelminae show great diversity in their behavior. Some are primary external parasitoids of larval or pupal stages of Homoptera, Coleoptera, Diptera and Lepidoptera. Anastatus and some species of Eupelmus are egg parasites of Lepidoptera, Orthoptera and Hemiptera. Others are hyperparasites of Braconidae and Tenthredinidae (Hymenoptera). Some species of Eupelmus attack either cynipid gall formers (Cynipidae, Hymenoptera) or Coleoptera and Diptera in plant stems and flower heads. Species of Metapelma are parasites of wood-boring beetles (Coleoptera). Members of the genus Arachnophaga are either parasites of spiders or primary or secondary parasites of Lepidoptera."

The North American species of Anastatus were revised by Burks (1967). Ashmead (1904) gave generic classifications of Eupelmidae, and Gahan (1943) and Bou…ek (1958) revised Arachnophaga.

PALEARCTIC (EUROPEAN former USSR).-- Trjapitcyn (1978/1988), as translated from the Russian, noted that these were "Medium-sized chalcids, about 3.0 mm long, but larger forms are known. Sides of mesothorax of female always convex and entire. Middle tibiae with long, thick spur. Sides of mesothorax of male divided. marginal and postmarginal vein of forewings long. Tarsi with five segments. Wings of female often short or reduced. A characteristic movable joint between the shield of the mesonotum and the scutellum permits a notable change in the shape of the thorax in females, on contraction of the longitudinal muscles; in this process the abdomen curves upward and forward. Host range very wide. Larvae usually ectoparasites; larvae of Anastatus parasitize eggs of insects. About 50 genera with more then 300 species are known in world fauna, predominantly in the tropics; in the European part of the USSR 8 genera with 31 species have been reported."

AFRICA.-- Prinsloo (1980) noted that this is one of the better known chalcidoid families from Africa, although knowledge of the group is confined mostly to taxonomic descriptions of a number of genera and species. Hedqvist (1970) catalogued the fauna of the Ethiopian region. Prinsloo (1980) further discusses Eupelmidae as follows:

Relationships & Diagnosis.-- "The Eupelmidae is most closely allied to the Encyrtidae and the two groups have in the past been placed in one family. These two families, together with the Tanaostigmatidae, are characterized by the large, convex mesopleura (in the case of Eupelmidae, only in females) and the strongly developed tibial spur of the middle leg. These families are easily separated in the keys by the position of the coxa and by the shape of the thorax."

"Moderate in size, usually about 2-4 mm in length, but also larger, up to 7 mm; body more or less slender, often partly or entirely refringent in colour; antennae in both sexes with one ring-segment and seven funicle segments, except in Neanastatus which has five funicle segments; mesoscutum in female always impressed, at least posteriorly, often with grooves or ridges; mesoscutum with parapsidal sulci absent or present; mesopleura in female large, convex, as in Encyrtidae; tibial spur of middle leg strongly developed, straight; tarsi five-segmented; middle coxa inserted close to hind coxa, at about posterior end of mesopleuron; fore wing with marginal vein long, at about posterior end of mesopleuron; fore wing with marginal vein long, usually much longer than the short stigmal and postmarginal veins; brachypterous forms often present; ovipositor sometimes protruding strongly; gaster sessile."

Biology.-- "Eupelmids are primary or secondary internal or external parasitoids of a wide range of insects. African species of Eupelmus have been reared, inter alia, from curculionid beetles, various species of Lepidoptera, including some of economic importance, cecidomyiid flies and other Diptera, and rarely also from soft scale insects. Some species have also been reared from braconid wasps, which indicates a hyperparasitic role. Anastatus apantelesi Risbec has been reared from the eggs of a charaxes butterfly, as well as from the cocoons of the braconid wasp, Apanteles. This suggests that A. apantelesi appears in the role of a primary internal parasitoid as well as secondary parasitoid, a rare phenomenon which is also known to occur in some non-African species of Anastatus. Most of the other species of Anastatus are, as far as is known, primary parasitoids with a wide host range, developing in the eggs of Hemiptera, Oothecae of cockroaches and mantids, and also in the eggs of various Lepidoptera. A. viridiceps Waterston parasitizes the puparia of the tsetse fly, Glossina morsitans Westwood and an undetermined species from southern Africa commonly attacks the eggs of the pine emperor moth, Imbrasia cytherea (F.). Bruchocida appears to be host specific in that all the species attack weevils associated with stored grain or seed beetles of the family Bruchidae. Other common genera such as Macroneura and Mesocomys are usually associated with Lepidoptera as their hosts, and Mesocomys pulchriceps Cameron is a well known natural enemy of various species of injurious saturniid moths, including Imbrasia cytherea, Gonimbrasia belina (Westwood), G. tyrrhea Cramer and species of Cirina."

African Eupelmide.-- "Some 170 species, belonging to 25 genera, have been recorded from the Ethiopian region. The family is usually divided into two subfamilies, the Eupelminae and Calosotinae. In the latter group, the mesoscutum is broad, transverse, much wider than the narrow pronotum, and the parapsidal grooves are usually indistinct in both sexes. In the Eupelminae, the mesoscutum is elongate, not much broader than the pronotum, distinctly impressed in the female, and the parapsidal sulci are distinct in the male. Most of the more common genera are easily recognized. Among the Eupelminae, Metapelma has the hind tibia foliaceously flattened; Neanastatus has only five funicle segments, whereas Anastatus usually has a pale crossband on the darkly infuscated fore wing, and differs from Eupelmus in that the gaster broadens towards the apex. Mesocomys is characterized by two triangular pits at the base of the scutellum, and in Bruchocida the head and body are covered with flattened, white setae. Macroneura is a common genus in which the wings are always reduced and the mesoscutum has two longitudinal carinae, one along each lateral margin. Genera of the Calosotinae are not as common as those of the Eupelminae, and the group is best represented in our region by the genus Calosota."

INDIA & ENVIRONS.-- Islam (1988) noted that "The eupelmids form a moderately large family comprising about 60 valid genera and approximately 700 species. This number is likely to be reduced further when the types of several little known genera from the Nearctic and the Australian regions are studied. The family, otherwise, forms a nearly homogenous assemblage of genera, related probably most closely to Encyrtidae. Eupelmidae can be distinguished from Encyrtidae by two characters: marginal vein of forewing longer, and the middle coxa with the thorax in profile, placed nearer the hind coxa than the fore coxa. The males of most eupelmid genera are rather very close to, and sometimes may be confused with, Pteromalidae."

"The known biologies show eupelmids as parasites or hyperparasites of pest species belonging to Lepidoptera, Hemiptera, Coleoptera and Diptera. However, taxonomic studies on the fauna of the Indian subcontinent are meagre and it will take some more years before a more or less clear picture of our fauna emerges."

History.-- "The earliest contributions to the family were made by Dalman, Walker, Westwood, Ratzeburg and Foerster. In 1896, Ashmead for the first time considered the family (there as a subfamily Eupelminae) on world basis and gave a key to the genera including several genera described as new in that paper. He again dealt with the family in his monumental work (1904), but hardly made any improvement over the key published in 1896."

"In the first half of this century, Girault, Ruschka, Bolivar and Gahan made important contributions to the family. Ferriere (1935-1954) dealt with the Palaearctic, Ethiopian and Oriental fauna of the family. His contributions on our fauna are noteworthy. The most notable contributions in the later half of this century were made mainly Hedqvist (1970) and Bou…ek (1967, 1976). The latter author also published a key to the genera of C.S.S.R. (In Peck et al. 1964), and more recently Trjapitzin (1978) gave keys to the genera and species of the family occurring in the european part of the U.S.S.R."

"The fauna of the Indian subcontinent is very little known, being represented by 10 genera and a few species. Some of the species are still little understood taxonomically and quite a few will prove to be synonyms."

AUSTRALASIA.-- Bou…ek (1988) noted that "The family name was introduced by Walker (1833: 368) but in Girault's time (following Ashmead, 1904a) the group was mostly classified as a subfamily of Encyrtidae. it seems beyond doubt that Eupelmidae developed from some primitive ancestors of Pteromalidae, as comparison with the pteromalid subfamily Cleonyminae suggests. The families Tanaostigmatidae and Encyrtidae seem to be derived in turn from Eupelmidae. The three families share, at least in the females, an enormous enlargement of the mesopleuron which forms a convex elongate shield... It is ventrally delimited by a deep horizontal groove and seems to correspond to the parts known in other chalcids as the subalar area and upper mesepimeron, and in some genera (e.g. Neanastatus) a fine subdivision of the shield is traceable. The development of the shield and other unusual features of the eupelmid thorax have been the subject of an extensive study by Gibson (1985, 1986b), who also analysed their implications for the classification of the eupelmids and related groups."

"The pleural shield developed apparently in conjunction with loosening of some other thoracic sclerites. In the most advanced forms (e.g. in Macroneura...) the thorax can suddenly contract, its transscutal suture springs upwards to form a transverse crest between the mesoscutum, which is sloping forwards, and the scutellum plus axillae, sloping backwards. At the same time the contracting muscles pull the head, pronotum and fore legs upwards close to the steep mesoscutum, and the gaster upwards against the steepened scutellum, whilst the mid legs luxate forwards in a very peculiar way. Among the adaptations for this purpose (which, it is believed, has something to do with jumping) the most peculiar is the attachment of the mid coxae. When they are in normal position a membranous area can be seen in front of them...; this area is absent in the Meatpelmatinae (mainly Old World) in which the middle legs cannot rotate forward, and in the pteromalid-like males of Eupelminae. Other features connected with the contraction are: the first axillary sclerite of the forewing (Gibson, 1986b) which appears in contracted specimens as a rounded projection between the base of the forewing and the axilla; the movement of the lateral margin of mesoscutum, sliding backwards along the mesopleural shield; the loosely connected metanotum which often shifts up and down along the hind scutellar surface (hence this is often shiny); the mobile complex of the propodeum and the metapleuron, often showing a gap between the latter and the apex of the pleural shield; and the mobile pronotum which is medially subdivided by a membranous line in the females of Eupelminae."

"The Eupelmidae are subdivided into three subfamilies, Calosotinae, Metapelmatinae and Eupelminae on the basis of the above characters. The Calosotinae are possible the most plesiomorphic of them (this seems to be supported by the fact that they develop mostly as parasites of xylophagous beetles), but all three subfamilies include some mixture of primitive and derived features. The Eupelminae are most peculiar as the males retain a 'pteromalid' appearance, not having developed a mesopleural shield. In Metapelmatinae the contracting capability is rather poor and the mid coxae cannot be rotated forward, not having the membranous anterior areas. Otherwise some generic characters seem to be correlated with specific niches, e.g. the cubical head with long scapes and very long body developed in a strikingly similar form in Exosandalum (Calosotinae), Hirticauda (Eupelminae, nr to Eupelmus), and one West Indian genus close to Brasema (Eupelminae nr Anastatus). Another example is the similarity of the body with a long ovipositor in Tineobius, Australoodera and the American Idoleupelmus Ashmead (the last genus has an apical rim on the gaster as in Anastatus)."

"An excellent account of the morphology and musculature of the thorax of Eupelminae was published by Gibson (1986b)."

"The diverse morphology of the group partly reflects what is known of the biology of the species, although only for a few species sufficient data are available. Calosotinae and Metapelma develop mainly as ectoparasites of wood-boring beetle larvae, but some species of Calosota develop instead in stems of Gramineae. In Eupelminae many Anastatus and species of some other genera attack eggs of Lepidoptera, Heteroptera, Orthoptera, Mantodea, Phasmodea and perhaps some other orders, but some species were reared from cocoons of other insects, especially of Braconidae and Ichneumonidae (Hymenoptera) which would place them perhaps as facultative hyperparasites. Eupelmidae are distributed in all continents, with more of forms in warmer countries than in colder temperate zones. In the Australian region they are represented by 19 genera. Of the genera classified by Girault in Eupelminae Neocalosoter belongs to Pteromalidae, Cerocephalinae. The Micronesian eupelmids figured in Yoshimoto & Ishii (1965: 141-163) may give the student some idea of the variation in the group but the generic names of most species now need to be corrected."

top of page

Biology & Behavior

Adult Behavior.

Riley (1874) described the habits of Anastatus mirabilis W. & R., calling it the "back-rolling wonder." Females have the habit of tumbling about after jumping and before gaining a foothold. Jumping behavior is well developed in Eupelmidae, and rather than flight, is probably the principal mode of locomotion. In A. amelophagus, females are apterous and males bear normal wings, while females of Eupelmella vesicularis have abbreviated wings. Various degrees of wing reduction are found in other species also (Clausen 1940/62).

A large number of eupelmids that are parasitic in eggs also feed on the fluids that exude from ovipositor punctures. Such feeding usually precedes oviposition, and stinging is often for the sole purpose of feeding. The stinging of many host eggs by A. disparis probably increases its force as a natural control agent (Parker 1933). In most cases the female merely consumes the egg fluids that exude, but in A. disparis, when feeding occurs on larvae or pupae of Ooencyrtus within the gypsy moth egg, a feeding tube is formed, which is also found in Arachnophaga when it attacks cocoons of Chrysopa. Female Anastatus axiagasti Ferr. punctures the egg, feeds and then wanders away, but she returns later, chews away the "cone" of dried fluids over the puncture and reinserts the ovipositor for laying an egg (Lever 1934). Adult Eupelmus popa seem to derive a portion of their food requirements from plant exudations (Woodruff 1929). They have been noted to feed on the hairy tips of feterita heads on which they were ovipositing. These tips are bound together with a gummy fluid not found elsewhere on the plant.

The true egg parasitoids, such as A. albitarsis, when oviposition occurs in eggs in which some embryonic development has occurred, the parasitoid egg is never placed within the embryo but is free floating in the egg fluids. Female A. albitarsis spend 15-30 min. during penetration of the heavy egg chorion of Dictyoploca, and initial penetration of the interior is exploratory. Eggs are never laid in a host egg containing either a nearly mature host embryo or an advanced parasitoid larva.

Eupelmids that are external parasitoids may place the egg only in the vicinity of the host rather than directly on it. In Eupelmus alynii French, about 1/2 the eggs are placed on the inner wall of the Harmolita cell. E. cicadae places its egg in the egg chamber of Cicada pleberja Fall, but external to the eggs. Female E. popa deposit the eggs on the hairs of the inner glumes of a spikelet of sorghum that is infested with Contarinia sorghicola Coq. Lecanobisu cockerelli Ashm. inserts the ovipositor by a backward thrust beneath the margin of an egg-bearing female of Saissetia oleae Bern. and places her egg among those of the host (Clausen 1940/62). A number of species of Eupelmus cover the egg with a fibrous network, a habit which was first observed in E. allynii (Packard 1916, Phillips & Poos 1921)) parasitic on the larvae of H. tritici Fitch, about half of the eggs being covered. The threads converge over the egg center, and it seems that the egg must first be laid on the wall of the larval cell opposite the point of penetration by the ovipositor and the strands are then fastened to the cell wall around the margin of the egg and drawn up to the center. The material from which this covering is formed is probably derived from the colleterial glands of the female parasitoid (Clausen 1940/62). A similar covering has been found in E. spongipartus, Eupelmella vesicularis and in Eupelmus sp. (Taylor 1937).

In species developing hyperparasitically, it has been found that the egg stalk serves as an organ of attachment. The stalk tip in the Anastatus pearsalli egg is always embedded in the ovipositor puncture in the integument of the Apanteles larva (Muesebeck & Dohanian 1927). The eggs of Eupelmella vesicularis deposited in Diprion cocoons are always found with their stalks fixed to the fibrous inner lining of the cocoon at the perforation point. Thus, they are suspended above the mass of Microplectron larvae, where they are protected from injury.

There is a relatively short oviposition period and the reproductive capacity is low. Females of Anastatus albitatsis deposit an average of circa 50 eggs during 15 days, and Eupelmella vesicularis averages only 20 (Clausen 1940/62).

top of page

Life Cycle

Egg incubation usually takes 2-5 days in summer, but the period may be greatly prolonged. Caffrey (1921) found that a portion of the eggs of A. semiflavidus persisted through winter. The time from egg deposition to larval maturity is only 10-20 days in most species, and winter is passed as mature larvae or prepupae. However, A. semiflavidus hibernates mostly as partly grown larvae, and feeding is completed in springtime.

There is usually only a single generation each year, corresponding to the host cycle. However, A. albitarsis usually produces a partial second brood in the infertile Dictyoploca eggs that remain after the healthy eggs have hatched, and several alternate hosts are known that are in the egg stage during midsummer. A. axiagasti, parasitoid of pentatomid eggs in the Solomon Islands, completes its cycle in 16 days and seemingly has a large number of generations each year. A portion of each brood persists in the larval stage until the second year in A. semiflavidus and Eupelmus cicadae. The period devoted to feeding is always relatively short, ranging from 1-2 weeks (Clausen 1940/62).

Sex Ratio & Parthenogenesis

Some species of Anastatus show a slight preponderance of females ranging to 2:1 under field conditions. There have been no males of Eupelmella vesicularis found in North America and females produce the same sex, generation. However, in Europe males are abundant in this species (Clausen 1940/62).

top of page

Immature Stages of Eupelmidae

There is little variation in form among the eggs of the representatives of the Eupelmidae. The main body of the egg is ellipsoidal and bears a stalk of varying length at the anterior end. In A. albitarsis (Fig. 58A), this stalk is only one third the length of the egg body and is robust and turgid after deposition. There is no pedicel or flagellum at the posterior end, but only a minute tubercle. In other species of this genus and in other genera, the stalk is longer, at times equaling or slightly exceeding the egg body, and more slender and there is a tapering "flagellum" at the opposite end of the egg (Fig. 60A). After deposition of the egg, the stalk is usually convoluted or sharply bent. The eggs of this family are relatively large, ranging from 0.3 tb 0.7 mm. for the length of the main body.

The first instar larvae of the genus Anastatus are distinguished by a rather elongated form and the development of the last abdominal segment into a bifurcated process. The extreme modification in form within the genus is revealed by A. albitarsis (Fig. 58B), found in lepidopterous eggs (Clausen, 1927). The paired processes of the tail are curved and heavily sclerotized and lie at right angles to the plane of the body. The second and third thoracic and the first seven abdominal segments each bear a trans­verse row of long spines ventrally at the anterior margin. Those of the first row equal about three body segments in length, and they diminish in size on the successive segments. Other species of the genus show the above characters in a lesser degree (Fig. 59A), though in some the ventral spines are not arranged in a distinct row and do not appreciably exceed the dorsal spines in length.

The larvae of Eupelmus and other genera in which the first instar is known lack the bifurcation of the caudal segment and have a relatively small number of spines. That of E. allynii (Fig. 60C) has two pairs of long spines dorsally on each body seg­ment except the last and one pair of smaller spines ventrally on each thoracic segment. The integument is densely clothed with minute setae. In Arachnophaga, one pair of spines is dorsal and the second lateral, just beneath the line of the spiracles. The integument of the dorsum and side bears numerous peg like projections. The larva of E. cicadae is slender, with a large and heavily sclerotized head, and the segmental spines are very much reduced in size. That of Eupelmella vesicularis bears two pairs of long heavy spines on each body segment, with an additional shorter pair on each of the thoracic segments.

The tracheal system of this instar normally bears four pairs of spiracles, which are situated on the second thoracic and the first three abdominal segments. In Eupelmus allynii, however, an additional pair is found on the metathorax.

Development of Larvae.

First instar larvae of A. albitarsis are able to readily move about in the semifluid host egg contents by repeated flexing of the body in the dorsoventral plane. The bifurcate caudal process, in junction with the ventral rows of spines, aids in movement through the medium. Such adaptations seem of limited importance when the larva is confined within an egg, but they may be useful to those species where development takes place externally on larvae. Species of Eupelmus and other genera that are external parasitoids of larvae in plant cells or in cocoons, show movement between two plane surfaces, and the long, stout spines may thus serve a locomotory function. In later instars there is less need to change position, and such characters are lacking (Clausen 1940/62).

Eupelmus cicadae deposits the egg in the egg chamber of Cicada, but externally (Silvestri 1918). The larva passes from one egg to another, sucking out the contents. The eggs in two or more chambers, situated close together in the twig, may be consumed by a single larva. The mature larva forms a channel or tunnel through the twig. When this is finished, the larva orients itself with the head toward the opening (Clausen 1940/62). Larvae of E. popa are predaceous on larvae and pupae of the sorghum midge, Contarinia sorghicola (Woodruff 1929). Newly hatched larvae of Eupelmus crawl from the hairs on the inner glume of the spikelet, where the eggs are laid, and search for midge larvae in the spikelet. First instar larvae are able to feed only on midge larvae, while later instars also attack pupae. Some larvae complete their development on a single host, while others require 2-3. Some larvae, after feeding on one host, complete their growth on plant sap, these individuals losing the reddish color that is characteristic of larvae that continue the entomophagous mode. They may be found embedded in cavities, usually many times their own size, and surrounded by shredded plant tissue resulting from lacerations of the seed during the feeding period. This is the only known case of plant feeding in the family, and the species is considered to be in an early transitional stage from an entomophagous to a phytophagous habit (Clausen 1940/62).

Eupelmus atropurpureus Dalm. is an external parasitoid on mature larvae of T. incertus Ratz. when the latter occurs singly in its host. When several are present within the remains of the alfalfa weevil larva, as is usually the case, it becomes a predator and consumes several or all of those which are found (Chamberlin 1925). The behavior of Eupelmella vesicularis, is similar (Morris 1938). The egg is deposited in a Diprion cocoon containing larvae or pupae of Microplectron fuscipennis, the latter ranging up to 100 or more. From 10-20 of these are consumed during larval feeding. At completion of feeding, Eupelmella larvae enter their most destructive phase and kill every Microplectron of all stages, including adults, that are found in the cocoon. Clausen (1940) noted that the repressive effect on the Microplectron is much greater than its size and numerical abundance indicate.

Taylor (1937) studying the larval behavior of Eupelmus sp., noted that the parasitoid is normally solitary and external on Elasmus and Tetrastichus, which develop on larvae of coconut leaf miners, Promecotheca spp., but it may develop also as a primary parasitoid on the latter. The newly hatched larva is quite active and may move about through the leaf mine and feed on several of the chalcidoid larvae if more than one is present. When attacking a primary larva that has not completed feeding, the Eupelmus larva consumes it and then continues to feed on the leaf beetle larva. Maturity may be attained after feeding on only a single larva of Elasmus, but full sized individuals arise only from larvae that have consumed several hosts (Clausen 1940/62).

The studies made upon Anastatus, Eupelmus and Eupelmella indicate that there are normally five larval instars, with the inter­mediate and final instars quite similar in form.

In Anastatus, there appear to be two forms of mature larvae, one being that of A. albi­tarsis (Fig. 61A) and A. semiflavidus, in which the body is robust, almost cylindrical, curved to conform to the egg in which it develops, and bearing only a few minute setae, and the other, represented by A. disparis and Anastatus sp. (Fig. 59B), which is almost spherical in form. The latter bears short spines on the thoracic segments and a larger number on the sixth to ninth abdominal segments.

In Eupelmus, Eupelmella and Lecanobius, the mature larva is rather elongated as compared with that of Anastatus. Eupelmus allynii (Fig. 60D) bears about seven pairs of long spines on the first thoracic segment, five pairs on the second and third, two pairs on the first five abdominal segments, and three pairs on the last five abdominal segments. Those on the abdomen are considerably shorter than the thoracic spines. Among the different species, the principal variation is in the size of these spines. The mandibles are simple. The number and position of the spiracles are constant in all the known genera, there being nine pairs, situated on the second and third thoracic and the first seven abdominal segments.

There is little variation in the form of the pupae within the family. Some have the body greatly curved, to conform to the outline of the egg in which they have developed, whereas others not so closely confined are more slender and the parts of the body are in the same plane. A. albitarsus is the only species known to possess the three fleshy processes on the head superimposed over the developing ocelli (Fig. 61B).

top of page