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HYMENOPTERA, Chrysididae (Dahlbom 1854) (Chrysidoidea) --  <Images> & <Juveniles> (Bethyloidea).


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Description & Statistics


           Chrysididae.-- Cuckoo wasps are small insects, rarely over 11 mm long.  Their color is metallic green or blue, and usually the body is  coarsely sculptured. They resemble some of the chalcids and bees in size and coloration, but a more complete venation in the front wing but no closed cells in the hind wing distinguish the cuckoo wasps.  Also the structure of the abdomen is distinctive and has only 3-4 visible segments and is hollowed ventrally. When a cuckoo wasp is disturbed, it usually curls up in a ball. Most species are external parasitoids of full-grown wasp or bee larvae; the species in the genus Cleptes attack sawfly larvae, and those in Mesitiopterus attack the eggs of walking sticks (Borror et al., 1989).


          The family Chrysididae is a very large cosmopolitan group (over 3010 described species) of parasitoid or cleptoparasitic wasps, often highly sculptured, with brilliantly colored metallic-like bodies (thus the common names jewel wasp, gold wasp, or emerald wasp are sometimes used). They are most diverse in desert regions of the world, as they are typically associated with solitary bee and wasp species, which are also most diverse in such areas.


          Species of the largest subfamily, Chrysidinae, are the most familiar; they are generally cleptoparasites, laying their eggs in host nests, where their larvae consume the host egg or larva while it is still young, then consuming the provisions. Chrysidines are distinguished from the members of other subfamilies in that most can curl into a defensive ball, in a process known as conglobulation. This ability is shared with pill bugs, pill millipedes (which are often mistaken for pill bugs), and armadilloes. Members of the other subfamilies are parasitoids, of either sawflies or walking sticks, and cannot fold up into a ball.


          Chrysididae are large and brilliantly metallic, usually green or blue, with coarse sculpturing.  They are known as ruby wasps, gold wasps and cuckoo wasps.  They are mainly solitary external parasitoids of vespoid and sphecoid Hymenoptera, although several are inquilines in the nests.  Most species attack hosts that form their nests or cells in exposed places, such as mud cells on walls, in crevices, etc., or those in hollow plant stems (Clausen 1940/62).  However, some species confine themselves to hosts that burrow in the soil.  Chrysis shanghaiensis Smith in 1940 was the single representative of the family known to be parasitic on larvae of Lepidoptera.  Clausen (1940) believed that generally Chrysididae should probably be considered more injurious than beneficial because of attack on hosts that store their nests with injurious insects and on hosts that are beneficial because of their habit of gathering nectar or pollen.  However, few species are abundant enough to be of much economic importance.


          Hymenopterous adult hosts of Chrysididae are often strong fighters, which may have been responsible for the development of defensive measures by the parasitoid, which are identical to those employed by many other animals having a heavy carapace.  Females when disturbed or attacked often roll themselves into a compact ball, remaining immobile and thus shielding the vulnerable body parts from injury (Clausen 1940/62).


          In chrysidids the head is hypognathous, the antennal flagellum has 11 segments; the pronotum has an anterior flange, and the propleuron is concealed in dorsal view (Finnamore & Brothers 1993).  The pronotum has the posterolateral apex usually well separated from the tegula, but sometimes it touches the latter.  The prosternum is small; metasoma with 5 or less exposed terga, rarely with a trace of the 6th.  Sexual dimorphism is usually very slight.  Both sexes are macropterous, rarely brachypterous or apterous; brachypterous and apterous species do not have the deep ventral constriction between the meso- and metathorax.


          This family has more than 3,000 species in four subfamilies:  Amiseginae, Chrysidinae, Cleptinae, and Loboscelidiinae.  Their greatest diversity is in temperate deserts of both hemispheres.  Adults are predominantly metallic green, violet and/or red, seldom brown or dull black.  If brown or black then sometimes they are partly dull red.  Larvae are parasitoids of the eggs or of the mature larvae of other insects or they are cleptoparasites in insect nests.  Pupation occurs within the host egg, cocoon, or nest. .


          Most species are primary, solitary, ecto- or endoparasitoids.  Immature stages usually develop on or within larval bees and nesting wasps, but some species feed as inquilines on the provisions stored in cells intended for the host larvae.  The family is of importance to biological control.


Biology & Behavior


          A detailed account of Chrysis shanghaiensis was given by Piel (1933a) and Parker (1936).  It is a solitary external parasitoid of mature larvae of the oriental moth, Monema flavescens Wlk., within its hard egg-like cocoon, in China and southern Japan.  This cocoon is too hard to be penetrated by the female's flexible ovipositor.  Instead, she bites a small hole in it with her mandibles, during which she slowly rotates the body about the point of attack.  The surface markings at the point of penetration are thus in the form of radiating lines.  When the hole is large enough, she turns around, inserts her ovipositor and stings the host larva in the thoracic region, causing permanent paralysis.  It is thought that stinging serves to halt development to the pupal stage rather than larval immobilization.  The egg is then laid loosely on the body, after which the female again applies her mandibles to the orifice, scraping from the surface of the cocoon material that, with the pellets set aside at the time the opening was made, is mixed with an oral secretion which serves to seal the aperture.  Parasitized cocoons are recognized by the radiating lines surrounding the point of penetration, which extend outward 1-2 mm.  This whole process from cocoon penetration to final sealing takes ca. 1 hr. (Clausen 1940/62).


          First instar larvae are active, and while feeding, use the bifurcate caudal process as a brace against the cocoon wall.  The mature larva spins a silken, golden cocoon within that of the host, and the meconium is discharged through the strands of the partly formed cocoon into the posterior region of the host cocoon, which contains the remains of the Monema larva.  Parasitoids always emerge from the anterior end of the host cocoon.  The cycle from egg to adult takes ca. 6 weeks, of which 2-4 days are required for egg incubation and a minimum of 11 days for the pupal stage.  The larval feeding period is followed by a rest period of about equal length.  In south China, the duration of the cocoon stage of the first generation is ca. 21-25 days.  Adults are long-lived, and females may persist in the field for several months.  However, reproductive capacity is low.  Parker in the laboratory obtained an average of only 11.3 eggs per female, and in China field parasitization reaches 50%.  There are two generations per year in south China, which corresponds to the host cycle, but only a single generation developed in the laboratory in Massachusetts.  Hibernation is as mature larvae.


          Chrysididae, which are parasitic on Hymenoptera usually, attack the host in the mature larval or prepupal stage and are not dependent at any time on the provisions contained in host cells.  Hicks (1933) found C. pacifica Say to oviposit at any stage of development of the larva of its host, Alcidamea brachyodonta Ckll., but the 1st instar larva delays its attack until the host cocoon is spun and the prepupa is reached.  Pleurocera viridis Guer. and Tetrachrysis carinata Guer. oviposit through the concrete-like cell wall of the Odynerus cell only after the cocoon of the latter has formed (Janvier 1933).  Penetration of the cell wall takes 1-3 hrs of effort with the ovipositor.  C. viridula L., attacking Odynerus, also usually chooses the less protected cells for oviposition and may lay eggs in those which are still open (Chapman 1869).  In closed cells, there is some indication that the mandibles are used in making the perforation.  Six to 10 eggs are placed on a host, with the surplus is destroyed by the larva hatching first.


          Behavior of C. lusca var. concinna Grib. differs decidedly from the above species (Bordage 1913).  The egg is laid shortly after that of the host, Sceliphron, and 1st instar parasitoid larvae and host engage in combat, after which the survivor develops on the prey contained in the cell.  If the host egg fails to hatch, the Chrysis larva dies without touching the food.  This suggests that the Chrysis larva dies without touching the food supply, and that the species is an obligate predator on the 1st instar larva of Sceliphron, and after this host has been consumed its food requirements are met by the spiders with which the cell is stocked.  In Chrysis dichroa Dhlb. developing in cells of O. rufohiria Latr. in Europe, the egg is laid in the cell before the latter is closed and on the food material at the opposite side from that occupied by the Osmia egg (Ferton 1923).  The parasitoid egg hatches shortly before the host, and though a number of eggs may be laid in a cell, only one larva survives past the 1st instar.  Usually the parasitoid will not attack the Osmia until larval development is complete, although sometimes the egg may be destroyed.  Similar habits were recorded for C. prodita, parasitic on O. saundersii Vach.


          A species of Chrysididae known to develop as an internal parasitoid is Pseudochrysis neglecta Shuck. (Maneval 1932).  The 1st instar larva penetrates the body of the partly grown larva of Osmia villosa Schnck. and develops coincidentally with it.  Internal feeding takes 20 days, and the host body contents are entirely consumed.


          All species spin a cocoon within the host cell, which in most cases is also within the host cocoon.  C. viridula first forms a mirrorlike diaphragm across the center of the host cocoon, that separates it from the host remains.  In this chamber the parasitoid spins its cocoon.  This characteristic seems common to the family.


          Developmental period from hatching to the completion of feeding is rather short for most species.  Egg incubation takes 2-5 days, and larval feeding up to 30 days.  The minimum is for C. ignita, which completes feeding within 6 days after oviposition.  In summer broods, a resting period intervenes before pupation.  A number of species have only one generation per year, but this seems correlated with the host.  Hibernation occurs as mature larvae in the cocoon.  The period of occurrence of adults in the field is often much shorter than that covered by the nesting activities of hosts, and a portion of the host population thus escapes attack. 


          Janvier (1933) described mating in T. carinata in Chile.  The male emerges earlier than the female and is able to detect the presence of his mate while she is still within the host cell.  When such a cell is found, the male attacks the cell wall with his mandibles, eventually making a way into the interior.  He then tears open the cocoon, and the female is seized by the thorax and dragged out of the cell, where mating takes place.


          For detailed descriptions of immature stages of Chrysididae, please see Clausen (1940/62).


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References:   Please refer to  <biology.ref.htm>, [Additional references may be found at: MELVYL Library ]


Finnamore, A.T. & D. J. Brothers. 1993. Superfamily Chrysidoidea (pp. 130-160). In GOULET, H. & HUBER, J. (eds). Hymenoptera of the World: an identification guide to families. Research Branch, Agriculture Canada, Ottawa, Canada, 668 pp.


Kimsey, L. S.  2006.  California Cuckoo Wasps in the Family Chrysididae (Hymenoptera.  Univ. of Calif Press. ISBN: 978-0-520-09857-2

Kimsey, L.S. & R. M. Bohart. 1990. The Chrysidid wasps of the world. Oxford University Press, Oxford, 652 pp.