Family Steinernematidae


(After Nguyen and Smart, 1994): Cephaloboidea, Rhabditida. Obligate insect parasites. Infective juveniles carry symbiotic bacteria in the bacterial chamber of the intestine. Both males and females are necessary for reproduction.

 Females:(FIG.SEM1) Large, size variable. Cuticle smooth or annulated. Lateral fields absent. Excretory pore distinct. Head rounded or truncate, rarely offset. Six lips present, partly r completely fused, each lip with one labial papilla (Fig. IA), sometimes additional papilla-like structures present near labial papillae. Four cephalic papillae. Amphids present, small. Stoma collapsed; cheilorhabdions pronounced, forming a ring resembling two large sclerotized dots in lateral view. Other parts of stoma forming an asymmetrical funnel with thick anterior end. Esophagus rhabditoid with metacorpus slightly swollen, narrow isthmus surrounded by nerve ring, and large basal bulb with reduced valve. Esophago-intestinal valve usually pronounced. Reproductive system didelphic, amphidelphic, reflexed. Vulva at mid-body, sometimes on a protuberance (Fig. 1B), with (Fig. 1C) or without (Fig. 1B) epiptygma. Females oviparous or ovoviviparous with juveniles developing up to the infective stage (IJ) before emerging from the body of the female. Tail longer or shorter than anal body width, with or without prominent phasmids.

 Males :(FIG.SEM2) Smaller than female. Anterior end usually with six labial papillae, four large cephalic papillae and usually with perioral disc. Esophagus similar to that of the female. Testis single, reflexed; spicules paired; gubernaculum long, sometimes as long as spicule; bursa absent. Tail tip rounded, digitate or mucronate. One single and 10 to 14 pairs of genital papillae present with 7 to 10 pairs precloacal.

 Infective juveniles (= third-stage infective juvenile):(FIG.SEM3): Stoma collapsed. Body slender, with or without a sheath (cuticle of second-stage juvenile). Cuticle annulated. Lateral fields present with 4-9 incisures and 3-8 smooth ridges . Esophagus and intestine appearing reduced. Excretory pore distinct. Tail conoid or filiform. Phasmids, located about mid-tail, prominent, inconspicuous, or not observed.

 Type genus:Steinernema Travassos, 1927

Syn.: Neoaplectana Steiner, 1929

 Other genus: Neosteinernema Nguyen & Smart, 1994

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