Steinernema scapterisci

Nguyen & Smart, 1990

Steinernema scapterisci emerged from a mole cricket


Males, first-generation

First generation male (FIG.1)much smaller than first generation female, but anatomically the two are similar anteriorly. Body usually plump. Head rounded continuous with body. Lips not seen but 6 labial papillae prominent, and 4 cephalic papillae well developed, much larger than cephalic papillae. Esophagus steinernematoid, procorpus cylindrical, metacorpus slightly swollen, isthmus distinct, basal bulb swollen with small valve. Nerve ring located in isthmus region of esophagus but position variable. Excretory pore located anterior to mid-esophagus. Excretory duct not forming elliptically-shaped structure present in females. Posterior part of body curved ventrally. Body assumes a spiral shape when killed by minimal heat. Gonad single, testis reflexed.Spicules (SEM) averaging 83 micrometers long, dark brown in color, paired, uniformly curved, with head large and somewhat angular. Angle formed by shaft and blade of spicules averages 110 degrees (range 100-120). Shaft of spicules long when compared to those of other species of the genus, and appears to be encased in a sheath; blade tapers smoothly to end with posterior portion thinner than that for other species of Steinernema. A small aperture can be seen on ventral side close to tip of the blade.Each spicule has two internal ribs with variable termination point proximally. Gubernaculum boat-shaped, with anterior part thin, long and ventrally-curved. Spicules glide along gubernaculum in two grooves separated by a needle-shaped cuneus. Cloaca on a raised area bearing an anterior flap, seen easily when the spicules are protracted or retracted. Eleven or 12 pairs and one single genital papillae observed.  One special pair located at the edge of cloaca. Tail with a mucron. No phasmid observed.

Tail of a male showing a special pair
of genital papillae.

Measurements: Length=1728 um SD=358 (1319-2271); Width=156 um SD=49 (97-231); EP=71 um SD=11 (63-98); NR=136 umSD=11 (120-152); ES=187 um SD=21 (164-216); testis flexure=374 um SD=52 (306-447); tail=25 um SD=3 (21-30); ABW=33 um SD=5 (31-45); mucron=4.3 um SD=0.6 (3.1-4.7); spicule length=83 um SD=5 (72-92); spicule width=13 um SD=4 (13-14); gubernaculum length=65 um SD=5 (59-75);gubernaculum width=8 SD=0.5 (8-9); D=36 SD=2 (32-39).

Abbreviations: um=micrometer; SD=standard deviation; EP=distance from anterior end to excretory pore; NR=distance from anterior end to nerve ring; ES=esophagus length; ABW=anal body width.

Males, second generation:Second generation male similar morphologically to that of the first generation except that it is about two-thirds as long and one-half as wide and the spicules have an elongate head.

Females,first generation

Anteriorly, female similar to male but much larger (FIG.2). Lateral fields and phasmids not observed.Six labial papillae and four cephalic papillae present. Stoma with prominent cheilorhabdions unusually thickened, appearing as a circular or hexagonal ring in face view. Esophagus typical of family. Esophago-intestinal valve large. Excretory pore located anteriorly to mid-metacorpus.

Excretory duct unusually prominent forming an elliptically-shaped structure seemingly with a hole at the center.Gonads didelphic, amphidelphic, reflexed. Vulva appears as a transverse slit with a prominent double-flapped epiptygma(FIG.21).Tail length shorter than anal body width, with a mucron at end.

Females, second generation: Second generation female similar morphologically to that of the first generation with the following exceptions: about one-half as long and two-thirds as wide, valve in basal bulb of esophagus more prominent, elliptically-shaped structure less prominent, tail, which tapers to a point bearing a mucron, longer than body width at anus.

Infective juvenile head showing
labial raising disc

Infective juveniles

( Third stage):The infective stage (FIG.3), when newly formed, is always enclosed in the cuticle of the second-stage juvenile as a sheath. However, the sheath is lost rather easily, even in storage, and thus may not always be present. Body thin, head with a labial raising disc; lip region not offset, oral aperture not observed; six labial, four cephalic papillae and an elevated oral disc prominent.Esophagus degenerate and thus not seen clearly, but its basal bulb is elongate and has a valve. Lateral field with 6 incisures. Tail tapers gradually dorsally but abruptly ventrally.

Measurements: L=572 um SD=27,(517-609); W=24 um SD=4, (18-30); EP=39 um SD=4, (36-48); NR=97 um SD=1 (83-106); ES=127 um SD=6 (113-134); tail=54 um SD=3 (48-60)a=24 SD=2.7 (20-31); b=4.5 SD=0.2 (4.0-4.6); c=10.7 SD=0.6 (9.2-11.7); D%=31 SD=3 (27-40); E=73 SD=6 (60-80)


The nematode found in the body cavity of the mole cricket, Scapteriscus vicinus, Uruguay, South America.


The nematode was originally found in Argentina, Brazil and Uruguay and recently in the United States. It was reported to infect an killed insects in the order Orthoptera: mole crickets of the genera Scapteriscus, Neocurtilla, house cricket, Acheta domesticus, field cricket, Gryllus sp., Grass hopper Romalea guttata; insects in the orders Coleoptera, Lepidoptera, Hymenoptera are poor hosts or non-hosts (Nguyen & Smart 1991, 1995).

Steinernema scapterisci emerged from a cockroach


The nematode can survive and still be infective in the absence of hosts for at least 10 weeks in moist soil (Nguyen & Smart 1990a).When infective juveniles (IJ) of Steinernema scapterisci were released on the soil surface in the field and in the laboratory, they moved downward through the soil at least 10 cm in 5 days, infected and killed mole crickets (Nguyen & Smart 1990b). When IJ were placed at the center of a 16-cm soil column, they moved in both directions with three times more moving downward than upward. In the field, nematode-infected mole crickets in the early stage of infection spread the nematode during their flight (Smart et al. 1991). Consequently, the nematode can be dispersed from inoculative field releases on golf courses and pastures (Parkman et al. 1993a, 1993b). The IJ enter the host through the mouth or spiracles (Nguyen & Smart, 1992).They develop in the host in the same way as other species of Steinernema. If the nematode number in a host is not overcrowded (nutrient supply is sufficient) the IJ develop to males and females of the first generation. Most eggs from these females hatch and the juveniles develop to become males and females of the second generation. Eggs produced from these females develop to IJ.This cycle takes 8-10 days. If the nematode number in a host is overcrowded (nutrient supply is insufficient), they develop to males and females of the first generation, and eggs produced by the females develop directly to IJ, this cycle takes 6-7 days.This nematode can develop between 15-33 o C.


Bacteria from Steinernema scapterisci cultured in vivo, in vitro and collected from fields were isolated and identified (Anguillera et al. 1993a).Many bacteria were associated with this nematode: Ochrobactrum anthropi, Paracoccus denitrificans, Xanthomonas maltophilia, Xenorhabdus bovienii, X. nematophilus, Xenorhabdus spp.These bacteria and three others, Pseudomonas fluorescens, P. aureofacians, and Escherichia coli were used for in vitro culture of this nematode. The nematode developed normally and produced IJ with all studied bacteria (Anguillera et al. 1993b).This fact shows that the nematode can feed on different bacteria, consequently, the nematode survives very well under field conditions.


Steinernema scapterisci is specific to mole crickets.The nematode was first released in Alachua County, Florida, where it became established and spread out to surrounding areas. Three years after the nematode was released, a few mole crickets collected in a farm 10 miles from the nearest released site were found infected with the nematode.By the fifth year, 25-65 % of the mole crickets collected at this farm were infected (Smart et al. 1990).The nematode was successfully introduced by inoculative applications in golf courses and pastures (Parkman et al. 1993, 1994) in FloridaSince 1993 this nematode has been commercialized in Florida to control mole crickets in golf courses and pastures.


ANGUILLERA, M. M., & G. C. SMART, JR.(1992). Bacterial symbionts of Steinernema scapterisci.Journal of Invertebrate Pathology, 62:68-72.
ANGUILLERA, M. M., & G. C. SMART, JR.(1992).Development, reproduction, and pathogenicity of Steinernema scapterisci in monoxenic culture with different species of bacteria. Journal of Invertebrate Pathology, 62:289-294.
NGUYEN, K. B., & G. C. SMART, JR. (1992).Life cycle of Steinernema scapterisci Nguyen & Smart, 1990. Journal of Nematology, 24:160-169.
NGUYEN,K. B., & G. C. SMART, JR. (1992). Addendum to the morphology of Steinernema scapterisci. Journal of Nematology ,24:478-481.
NGUYEN, K. B., & G. C. SMART, JR. (1991a).Pathogenicity of Steinernema scapterisci to selected invertebrates. Journal of Nematology, 23:7-11.
NGUYEN, K. B., & G. C. SMART, JR. (1991b). Mode of entry and sites of development of Steinernema scapterisci. Journal of Nematology, 23:267-268.
NGUYEN, K. B., & G. C. SMART, JR. (1990a).Preliminary studies on survival of Steinernema scapterisci in soil. Soil and Crop Science Society of Florida, Proceedings, 49:230-233.
NGUYEN, K. B., & G. C. SMART, JR. (1990b). Vertical dispersal of Steinernema scapterisci. Journal of Nematology, 22:574-578.
NGUYEN, K. B., & G. C SMART, JR.(1990).Steinernema scapterisci n. sp. (Steinernematidae: Nematoda). Journal of Nematology, 22:187-199.
PARKMAN, J. P., J. H. FRANK, K. B. NGUYEN, & G. C. SMART, JR. (1994).Inoculative release of Steinernema scapterisci(Rhabditida: Steinernematidae) to suppress pest mole crickets (Orthoptera: Gryllotalpidae) of golf courses.Environmental Entomology, 23:1331-1337.
PARKMAN, J. P. J. H. FRANK, K. B. NGUYEN, & G. C. SMART, JR. (1993).Dispersal of Steinernema
scapterisci (Rhabditida: Steinernematidae) after inoculative applications for mole cricket (Orthoptera: Gryllotalpidae) control in pastures. Biological Control, 3:226-232.
SMART,JR., G. C., & K. B. NGUYEN (1995).Biological control of Orthoptera pest insects. United State Patent, patent number 5,466,448, date of patent: November, 14 1995.
SMART, G. C. JR.,K.B. NGUYEN, J. P. PARKMAN, & J. H. FRANK (1990).Biological control of mole crickets in the genus Scapteriscus with the nematode Steinernema scapterisci Nguyen & Smart, 1990. Rencontres Caraibes en lutte biologique, Guadeloupe, 5-7 November 1990. Ed. INRA, Paris 1991.

This document was constructed and is maintained by KHUONG B. NGUYEN
Entomology & Nematology Department
University of Florida