Perilampidae (Forster)

Description & Statistics

Perilampidae is a relatively small cosmopolitan family with circa 25 valid genera and 212 species known by 1993. They are primarily tropical in distribution. Important morphological characters include a 13-segmented antenna, filiform, with one annulus and a 3-segmented club; thorax large, bulging, pitted with punctures; parapsidal sutures deep and complete. They have a short petiole; the abdomen is small and triangular in profile, shiny; body is usually metallic blue, blue-black or green; scutellum is often with 2 small rearward projections; prepectus is large and fused to the pronotum, the latter being with a well defined collar.

Most Perilampidae are hyperparasitoids of Lepidoptera larvae through a variety of dipterous, e.g., tachinid or hymenopterous (braconid and ichneumonid) primary parasitoids. Some species are primary parasitoids; others are phytophagous. Phytophagous species are mostly confined to Australia. Both endo- and ectoparasitic species are known. Most are considered solitary. No perilampids have been used in biological control.

Further Description.

Entomophagous species in this family are almost all hyperparasitic on Lepidoptera through Diptera and Hymenoptera. A number of phytophagous species have been included in the family, whose placement was questioned by Clausen (1940). Host preferences of Perilampus spp have been discussed by Smith (1912). A number of species of this genus are also known to be primary parasitoids of Coleoptera, Lepidoptera, Neuroptera and Hymenoptera. However, again Clausen (1940) questioned the validity of this for most cases, although Boselli (1932) found P. italicus F. to be a true external parasitoid of Athalia colibri Chr. larvae in their cocoons and Smith (1917) found P. chrysopae Cwf. to develop externally on the pupa of Chrysopa in its cocoon. Clausen (1940) concluded that it is thus possible that some of the records of direct parasitization of gall making and stem infesting Lepidoptera and wood boring Coleoptera and may be correct.

Perilampus hyalinus Say is an indirect parasitoid of Hyphantria textor Harr., through Ernestia ampelus Wlk. (= Varichaeta aldrichi Tns.) and other dipterous and hymenopterous parasitoids (Smith 1912). Perilampus tristis Mayr. is indirectly parasitic through various ichneumonid and tachinid primary parasitoids on European pine shoot moth, Ryacionia buoliana Schiff. (Bergold & Ripper 1937). Perilampus chrysopae was studied by D. W. Clancy, with details given in Clausen (1940).

Specific Geographic Areas

NEARCTIC (CANADA).-- Yoshimoto (1984) considered Perilampidae a subfamily, Perilampinae, of the Pteromalidae. He stated that it "resembles the family Eucharitidae in that the prepectus is fused to and lies in the same plane as the lateral part of the pronotum, and also that the thorax is usually convex and bulging. The ...family is recognized by the following characters: Body often 2-3 mm long, robust, sometimes metallic. Pronotum narrow, prominent in dorsal view. Gaster nearly triangular (except Steffanolampus Peck); tergite 1 fused middorsally to tergite 2, with lateral margins free and overlapping. Thorax frequently with umbilicate or thimblelike punctations. Gaster subsessile, with short inconspicuous petiole (except for males of Perilampus fulvicornis group, i.e., P. muesebecki and P. prothoracius; Burksilampus Bou…ek is not yet known from Canada); antennae stout, 13-segmented (1 anellus, 7 funicle segments, 3 club segments). Frons deeply depressed."

"Four genera of ...[Perilampidae]..are known from North America; Perilampus Latreille, Euperilampus Walker, and Steffanolampus Peck are known from Canada. These may be distinguished by means of the key to world genera provided by Bou…ek (1978). The perilampids are given subfamily status by Bou…ek, following Riek (1966), but as stated by Bou…ek, 'it is premature to discuss their familial rank,...'" He thus treated them as a subfamily of Pteromalidae.

"The species of Perilampus of North America were revised by Smulyan (1936). Crawford (1916) described eight species and provided a key to known species of Perilampus of America north of Mexico. The genus Steffanolampus is monotypic, its only species being S. salicetum (Steffan), which is a parasite of wood-boring beetles, primarily Anobiidae (Coleoptera). Species of Perilampus are hyperparasites on Lepidoptera and Orthoptera (in Canada), and Embioptera and Neuroptera (in tropical regions) through dipterous and hymenopterous primaries. A few species are primary parasites of Hymenoptera (e.g., Diprionidae), Coleoptera (e.g., Curculionidae), or Neuroptera (e.g., Chrysopidae). As in the Eucharitidae the adult females do not lay their eggs directly on the ultimate host, but on plant foliage. First-instar planidiform larvae attach themselves to any moving object. As primary parasites, the planidia enter the host, remain as planidia until the host pupates, then exit from the host, feed externally, and pupate. Those species that are secondary parasites of primary Diptera and Hymenoptera parasites, enter the secondary host larva where they search for and enter the body of the primary parasite. Again, development ceases until the primary parasite exist from the host and pupates. At this time the perilampid parasite takes up an external position on the pupa and continues development (Clausen 1940)."

PALEARCTIC (EUROPEAN former USSR).-- Trjapitcyn (1978/1987), as translated from the Russian, described this family as, "Chalcids of medium size; body usually 2.0 to 4.0 mm long, rarely up to 8.0 mm (Philomides). mandibles with two or three teeth. Antennae with 13 segments, filamentous or slightly flat, with one ring and three-segmented clava. Thorax usually highly convex. Ovipositor does not protrude. Body usually with metallic glaze, rarely more or less yellow. Larval parasites, usually secondary, found in cocoons of Lepidoptera, sawflies, Neuroptera, and some beetles, and puparia of parasitic insects. Development of Perilampus undergoes hypermetamorphosis with exposed, planadium or 1-instar larvae. To date no more than 10 genera are known in world fauna; Soviet Union, 3 genera with about 20 species (of which 2 genera with 15 species found in the European part of the USSR)."

AFRICA.-- Prinsloo (1980) noted that the systematic status of this family is not clear. usually, the genera of the Perilampidae are divided into two groups or tribes, the Perilampini and Chrysolampini. Most authors regard the Chrysolampini as belonging to the Pteromalidae, leaving the Perilampidae with only the species of the Perilampini. The two tribes have also been grouped together in the subfamily Perilampinae under Pteromalidae. Only species of the Perilampini, which we may regard as 'true perilampids,' are dealt with here. These Perilampidae in the Ethiopian region are contained in three genera."

Diagnosis.-- "Medium to fairly large chalcidoids; body robust; the thorax strongly convex; colour refringent; thorax often coarsely pitted, but also striate; prepectus fused with lateral part of pronotum; antenna short, thirteen-segmented, with one ring-segment and seven transverse funicle segments; fore wing venation well developed; gaster of distinct shape with dorsum consisting of two fused basal tergites which are laterally separated, giving the gaster a triangular appearance in lateral view; ovipositor in female at most slightly exserted caudally; tarsi with five segments."

Biology.-- "Not much is known about the biology of the African perilampids, but they are probably, like the majority of non-African species, usually hyperparasitoids; this is known to be true in the South African Perilampus rostratus Kerrich which develops from the pupae of the following four Íchneumonoidea, all parasitic on the Karoo caterpillar, Loxostege frustalis Zeller: Macrocentrus maraisi Nixon, Chelonus curvimaculatus Cameron, Cremnops frustalis Nixon, and Temelucha picta (Holmgren). Species of Monacon are known to be parasitoids of platypodid beetles."

African Perilampidae.-- "Of the three genera recorded from Africa, namely Euperilampus, Monacon and Perilampus, the latter is most common and best known. Monacon is readily separated by a conspicuous horn-like process on the face, placed just below the antennae, whereas Euperilampus is distinguished from Perilampus by the postmarginal vein of the fore wing which is longer than the marginal vein."

INDIA & ENVIRONS.-- Subba-Rao (1988) noted that "The perilampids are a small group of parasitic insects, nonetheless, they are very important as most of the species whose biology has been studied are at least in part secondary parasites. Some species of the family are easily recognized as their body is usually robust, mostly metallic in colour; the thorax is usually high and convex, most frequently with umbilicate sculpture; gaster sometimes petiolate, with the first tergite usually fused dorsally at the hind margin to the second tergite, but not fused laterally, with the result that the gaster appears triangular in dried specimens."

History.-- "It is sufficient to note that the family is poorly represented in the Indian fauna and needs further studies. Whatever is known is mainly due to the contributions of Mani & Kaul (1973, 1974) and Bou…ek (1978, 1980). Presently it is represented by four genera and nineteen species."

Classification.-- "Whether perilampids are recognized as a family on its own, or placed as a subfamily of Pteromalidae is still debatable. I have treated the group as a family, and excluded Philomidinae and Chrysolampinae; the former is referred to Eucharitidae and the latter to Pteromalidae."

AUSTRALASIA.-- Bou…ek (1988) noted that "The name was proposed as family 'Perilampoidae' by Förster (1856: 19, 22) for genera belonging now to the two subfamilies."

"The group as a whole is difficult to define by simple tangible characters. This eventually led to the transfer of Chrysolampinae to Pteromalidae, first by Peck, 1951: 539 (under Lamprotatini). The transfer was probably based just on a similarity in the petiolate gaster and the decision was later reversed (Bou…ek, 1956b; Peck, 1963). Then Graham (1969: 86-92) treated Chrysolampinae as a subfamily of Pteromalidae. However, the chrysolampines resemble Perilampinae and although Graham regarded the resemblance as superficial, Riek (1966b: 1970: 921) logically concluded (Bou…ek, 1972a: 94) that both groups should be placed in Pteromalidae. A recent attempt at a cladistic analysis of the larval morphology (Heraty & Darling, 1984) seems to agree with a previous hypothesis (Bou…ek, 1956b) that Chrysolampinae probably branched off from an early stem of the pteromaloid ancestors. They are probably the plesiomorphic sister-group of Perilampinae and if this is right the two groups should be classified together."

"For biological characters see under the two groups. The family has only a dozen genera and 8 of them occur in the region."

top of page

Biology & Behavior

Adult Perilampidae are often found at flowers, especially those of Compositae, and on aphid infesting foliage where they seem to feed on the honeydew. Females of P. italicus puncture the leaf epidermis with the ovipositor to feed on sap which exudes, and in the laboratory feeding is extensive on sugar solution. Smith (1912) did not find the manner and place of egg deposition in P. hyalinus, although he believed that it occurred on the food plant in the vicinity of a colony of caterpillars. Smith (1912) did actually observe oviposition in P. chrysopae. Females of this species hover over foliage of oleander that is infested with Aphis nerii Kalt. where Chrysopa larvae are feeding. They were observed to touch the leaf surface with the abdomen at times, when eggs were deposited. Such eggs were lightly attached to the leaf by the posterior end. Clancy found that the aphids and mealybugs rather than the Chrysopa, provided the oviposition stimulus.

A modification in oviposition habit of P. italicus was noted by Boselli (1932), where individual eggs were partially embedded in incisions in the leaf epidermis. These incisions were made in series at intervals of 20-40 seconds. P. tristis oviposited on the upper sides of oak leaves in the laboratory (Parker 1924).

Reproductive capacity is high, although not comparable to that of related Eucharidae. One female of P. chrysopae was found to deposit 52 eggs in one day, and Clancy stated the total production ranged from 200-500 (Clausen 1940/1962). Bergold & Ripper (1937) found that females of P. tristis had 56-94 ovarioles each containing 3-4 mature eggs. The total number of eggs available for deposition at one time is thus over 100. About 250 mature eggs were found in ovaries of P. hyalinus by Smith (1912). A long gestation period was indicated by the absence of eggs in newly emerged females, however.

top of page

Immature Stages of Perilampidae

The egg of P. chrysopae (Fig. 51 top) is subcylindrical and distinctly arched on one side with one end rather sharply pointed and the other bearing a short, broad pedun­cle. It is pearly white in color, and the chorion is characteristically sculptured, with irregular elongated areas that extend lengthwise. The eggs of P. tristis (Fig. 51 bottom) and P. italicus are very similar. The size of these eggs, which measure 0.25 mm. in length in P. chrysopae and 0.41 mm. in P. italicus, contrasts strongly with the very minute stalked eggs of the related Eucharidae.

Eggs of P. chrysopae hatch in 4-6 days under summer temperatures, and 14-15 days in P. italicus at fluctuating temperatures of 16-38°C. Upon emergence from the egg, the planidium undergoes a free living period while it searches for hosts. In Perilampidae and Eucharidae Clausen (1940) remarked that this is more a waiting rather than a searching time, for little movement takes place and most time is passed in the erect position awaiting the host or carrier. P. chrysopae planidia were kept alive 17 days without food, during which time they did not change their positions. In the field planidia are often found attached to the egg stalks of Chrysopa, this position giving them an opportunity to transfer to the newly hatched 1st instar host as it descends the stalk in search for food. Generally, the planidium does not show sufficiently developed instincts for proper host selection, but responds virtually to any moving object in its vicinity.

Perilampidae that develop as primary external parasitoids, as in P. chrysopae, have planidia that attach to the host at any stage of larval development. Not much feeding takes place as long as the host remains in the larval stage, and host pupation occurs normally. Clausen (1940) remarked that Clancy found that the normal host of P. chrysopae was C. californica Coq. It was unable to develop to maturity on C. majescula Banks that is present in the same areas. Despite this, the planidia attach themselves to larvae of the latter, and instances were noted where they survived on them for 5-6 months without development.

The first instar larvae of Perilampus are all of the planidium type, with heavy segmental bands that almost reach the median ventral line. There are 13 body segments, of which the first 12 bear the sclerotized bands and the 13th is represented by the caudal sucker. Specific differences occur in the form of the terminal portions of the bands and in the number, size, and position of the body spines and the "scales" and hooks on the membrane of the venter of the anterior portion of the body. The pleural plates, which have been distinguished upon the planidia of the Eucharidae and of families of other orders having larvae of this type, are absent or not recognizable.

On the larvae of P. hyalinus (Fig. 52A) and several others, the posterior margins of the terminal portions of each band bear numerous sharp teeth, whereas in P. chrysopae (Fig. 52B) they are smooth. The sensory spines are exceptionally long and heavy in the latter species. The two caudal cerci arise dorsolaterally from the last segmental band. In Perilampus sp. from Conocephalus (Ford 1922), they are about 1/2 the length of the body.

Spiracles have been detected in P. hyalinus, P. chrysopae, P. tristis and several undetermined species; all these except the first have a single pair dorsolaterally at the anterior margin of the band of the second thoracic segment or on the membrane between the first and second segments. In P. hyaiinus, the spiracles are on the intersegmental membrane but distinctly ventral.

Parasitism effects the minute planidium on the tachinid pupa conspicuously and out of proportion to any mechanical injury that is inflicted at emergence or to the very small amounts of fluids taken from the body. The pupa becomes distinctively translucent, especially in the head and thorax, the head attains only 1/2 its normal size, and the eyes and appendages develop only slightly. it is thought that the small emergence wound at this critical time causes an upset in equilibrium of body fluids, which results in almost complete cessation of development (thompson 1915).

The number of larval instars is uncertain. Smith recognized only three in P .hyalinus, while Parker described four for the same species and Bergold & Ripper found the same number in P. tristis.

The second instar larva of P. hyalinus (Fig. 53B) lacks the specialized characters of the first instar, and the body is white and distinctly segmented. The sensory setae are small and set upon tubercles, and each segment bears a band of minute integumen­tary setae at the anterior margin. The two pairs of large spiracles are situated on the mesothorax and the first abdominal segment. The larva of P. chrysopae (Fig. 53A) is similar, though more robust, but in P. tristis the spiracles are said to be on the pro­- and metathorax.

The third instar larva of P. hyalinus (Fig. 53C) is rather indistinctly segmented but still bears the sensory and integumentary setae mentioned for the second instar. There are now seven pairs of spiracles, situated on the last two thoracic and the first five abdominal segments, of which the first and third are largest. In P. tristis, the number and position are the same.

The fourth instar larva of P. hyalinus (Fig. 53D), which is the mature form, is distinctive, being very robust and bent ventrally in the thoracic region, with large lateral segmental "bosses" on the first 5 abdominal segments and distinct fleshy tubercles of testaceous color at the lateral margins of the second and third thoracic segments. The sensory and integumentary setae of the preceding instars persist. There are nine pairs of spiracles, the additional two pairs being on the sixth and seventh abdominal segments. The larva of P. tristis is similar except that the thoracic tubercles occur on all three segments.

Interactions between Perilampus and its hosts are much different when development is in the secondary role on various ichneumonid, tachinid and braconid parasitoids of caterpillars and sawflies. In a study of P. hyalinus and its host the tachinid Ernestia ampelus, the latter deposits living maggots on foliage in the vicinity of Hyphantria caterpillar colonies. They penetrate the skin and enter the body cavity of the caterpillar at first opportunity. The planidia of Perilampus are also free living on the foliage at the same time and enter the caterpillar body in the same way. Although the possibility of direct entry of Perilampus planidia into the 1st instar larva of Ernestia while it is still on the foliage is not verified, its relative size and simultaneous occurrence on foliage in the vicinity of caterpillar colonies could permit direct parasitization (Clausen 1940/1962). The Perilampus planidium that enters the caterpillar body searches for the larva of a primary parasitoid, in this case Ernestia, which is entered in turn. There is stays apparently without feeding, until the maggot reaches maturity, leaves the caterpillar and pupates in the soil during late summer or early autumn. Right after formation of the puparium, the planidium emerges from the body and takes up an external position on the pupa, where it remains, again apparently without feeding, through the winter. With warmer weather in springtime the planidium begins feeding. As growth progresses the segmental bands become widely separated and conspicuous against the white background of the body contents, which are revealed through transparent intersegmental membranes. At 25.5°C the first molt occurs circa 6 days after feeding begins, and larvae mature in circa 17 days, followed by a pupal period that lasts 10 days (Clausen 1940/1962).

The pupae of the different species are short and robust, with the abdomen almost spherical and bearing transverse intersegmental welts similar to those of some Eucharidae.

Histolytic changes taking place in the host body at pupation were considered responsible for stimulating the initiation of rapid feeding and growth. Host pupae become inactive during either the late 1st or the 2nd larval stage of the parasitoid, and paralysis is accompanied by a reduction in the amplitude and rate of heart beat, which is probably induced by the injection of a toxin into the body (Clausen 1940/1962).

Boselli (1932) found that behavior of P. italicus as a solitary external parasitoid of A. colibri was about the same as that of P. chrysopae, although the host did not attack the pupal stage.

When Perilampus parasitizes Eulimneria valida Cress, an ichneumonid parasitoid of Hyphantria, it adapts to the changed conditions and persists internally in the mature larva through winter. Emergence and external feeding occurs only after Eulimneria begins its transformation to the pupa in springtime.

The behavior of P. tristis differs considerably from that of P. hyalinus. This parasitoid attacks a number of Ichneumonidae and Braconidae which are internally parasitic on larvae and pupae of Rhyacionia buoliana (Bergold & Ripper 1937). The Rhyacionia has only one generation per year and passes winter as half grown larvae in pine shoots. The planidia of P. tristis enter young caterpillars during August and September, and shortly thereafter are found in the fat body or salivary gland. With the resumption of activity in springtime, they may often occur attached externally to the young larvae of the primary parasitoids, but they soon enter the body cavity and await the attainment of the pupal stage which occurs during June, after which they become ectoparasitic and complete development in circa 1 month.

top of page

Life Cycle.

The life cycle is dependent on the host stage to which the planidium attaches and among hyperparasitic species, upon the time required for the primary host to pupate. P. hyalinus, parasitic on Ernestia, has one generation per year, as does P. tristis in several species that attack the pine shoot moth. In both species, winter and much of the year are passed as an inactive 1st instar larva. Smith (1912) believed that Perilampus, when developing as a parasitoid of summer active Tachinidae, attained the adult stage in autumn and hibernated as such within the host cocoon or puparium. Perilampus cuprinus Foerst. in Europe has this behavior. Clausen (1940) commented that it is probable that the above species produced several generations per year on multibrooded hosts. Clancy ((Clausen 1940/1962) found that P. chrysopae was able to complete the life cycle in a minimum of 18 days, of which the egg, larval and pupal stages required 1, 8 and 6 days, respectively. The very short cycle was made possible by direct attack on a host that also had a short cycle and was initially attacked in its mature larval stage. Winter is passed as pupae.

top of page