TWO NEW SPECIES OF LONGIDORIDAE (DORYLAIMIDA) FROM SAUDI ARABIA BY P. A. A. LOOF Landbouwhogeschool, Wageningen, Netherlands Two new species of Longidoridae are described from poorly growing date palms in Saudi Arabia. Longidorusorientalis n. sp., found in Dirab and Riyadh, (and also in soil around roots of grapevine in several localities in Iraq) is characterized by round, continuous lip region, bilobed amphids and hemispherical female tail, body length of 4-6 mm and odontostyle length of 96-113 µm. L. taniwhaapud About-Eid, 1970 from Egypt is possibly identical with it. Xiphinemaphoenicis n. sp. closely resembles X. diversicaudatum(Micoletzky, 1927), but is distinctly more slender ("a" being 83-124 in females, 92-126 in males; in diversicaudatum67-84 in females, 66-92 in males), the vulva is more posterior (45-51 vs 38-46), the odontophore is shorter relative to the odontostyle, and the females possess a well developed, more compact Z-organ. X. phoeniciswas found only at Riyadh, together with numerous specimens of Longidorusafricanus Merny, 1966, and a few L. sid- diqii Aboul-Eid, 1970 and Xiphinemaitaliae Meyl, 1953. Keywords.Longidorus, Xiphinema, taxonomy, date palm. In 1980 Dr. M. F. M. Eissa, then at Riyadh, Saudi Arabia, sent some tubes with longidorid nematodes from date palm at the Regional Agriculture and Water Research Centre, Riyadh. The trees, twenty years old, of local cultivars, were in poor condition. The samples contained three species of Longidorus and two of Xiphinema. Another sample was sent from Dirab, 35 km west of Riyadh, from a new date palm orchard which had failed. This sample contained one species of Longidorus (which was present in the Riyadh samples as well). This species occurred in high densities: 200-400 specimens per 250 ml of soil, and was considered the cause of the failure. Dr. Eissa (in letter of April 4, 1982) commented upon this: "(This high population of Longidorus), in addi- tion to other stresses (aridity, high contents of salts in irrigation water, lack of fertilizers, low fertility of land and lack of manuring and proper horticultural practices etc.) causes crop failure. Date palm tolerates to some extent severe adverse conditions. When those exceed its tolerance limits, depending upon the cultivars growth stops and the apical buds collapse, mostly when the trees are 30-40 years old. Visible symptoms of lost water balance to the date palm head are foliage chlorosis, irregular drying of the top and twist in the prevailing wind direction.... Former visiting scientists call this case Al-Wijam and relate it to a physiological unexplained cause." The five species found were: Longidorus africanus Merny, 1966 (Riyadh, 204 specimens) L. siddiqii Aboul-Eid, 1970 (Riyadh, 3 specimens) 308 L. orientalis n. sp. (Riyadh, 19 specimens; Dirab, 19 spec.) Xiphinema italiae Meyl, 1953 (Riyadh, 5 specimens) X. phoenicis n. sp. (Riyadh, 112 specimens). The two new species are described hereunder. Longidorus orientalis n. sp. (Fig. 1 and 2) Females (n = 10: 3 from Riyadh, 7 from Dirab): L = 4.04-5.03 mm; a = 82-105; b = 9.3-13.5; c = 150-183; V = 7-1545-546-15; odontostyle = 99-104 Am; odontophore = 59-78 Am; spear = 163-182 Am; guiding ring from head end (GR) = 27-33 gm; c' = 0.7-0.9; pre-rectum = 352-746 Am or 8.4-20.5 anal body widths. Female, holotype: L = 4.93 mm; a = 93; b = 13.5; c = 155, V = 7506 ;'odon- tostyle = 100 Am; odontophore = 65 Am; spear = 165 Am; GR = 33 c' = 0.8; pre-rectum = 352 Am or 8.4 ABW. Males not found. Body curved ventrally in death, in some specimens coiled into a spiral; cylin- drical over the greater part of its length; body width at vulva 1.3-1.7 anal body widths. Cuticle 3 Am thick in mid-body, 4 gm in anterior part of neck, 6 Am on base of tail and 12-14 Am on terminus; with distinct outer layer; on the ter- minus only the inner layer is thickened. Subsurface transverse striae almost imperceptible; slightly more pronounced on tail and there becoming radial. Lateral chord 1/3-1/4 of body width. There are about 9 lateral pores in the oesophageal region; 35-40 between oesophagus base and vulva; 40-50 between vulva and anus and two on the tail. Total number of pores on one side of the body about 100. From the base of the oesophagus to the anterior end of the pre- rectum the pores are spaced rather regularly. Lip region rounded, 10-11 Am wide, not offset in any manner. Amphids evenly bilobed, extending about two-thirds the distance from head end to guiding ring; the aperture could not be seen. Guiding ring and odontostyle typical for genus; odontophore simple. The oesophageal bulb measures 105-122 Gland nuclei: DO 12-16 % ; DN 30-38%; SN 46-57%; SO 80-88 % . There are two nerve rings: one very narrow, just anterior to the base of the odontophore, associated with the hemizonid and also with a dorsal com- missure ; the other is broader and lies about 20 Am more posterior. Cardia rectangular, 11-13 x 8-9 Am. Vulva a transverse slit 15 Am long. Vagina about one-half body width deep. Genital tubes amphidelphic, reflexed. Uteri rather undifferentiated, without sperm. The sac connecting the ovary with the oviduct varies enormously in length, which probably is connected with the great length of the eggs. The longest sac seen measured 450 gm. Oviduct extremely long (145-220 Am ex- cluding sac), in some specimens extending far beyond the ovary. Dimensions .