Life history and description of immature stages of Neaspilota signifera (Coquillett) (Diptera : Tephritidae) on Hemizonia pungens (Hooker and Arnott)Torrey and A-Gray (Asteraceae) in southern California

Neaspilota signifera (Coquillett) is a bivoltine, monophagous fruit fly (Di ptera: Tephritidae) apparently developing solely in the flower heads of Hem izonia pungens (Hooker and Arnott) Torrey and Gray in southern California. The egg, first-, second-, and third-instar larvae, and puparium are describ ed and figured. The mouth-hooks of the first and second instars are bidenta te, but tridentate in the third instar. The pair of flattened integumental petals are fused laterally with the well developed, stomal sense organs in the first instar; whereas, the integumental petals are papilliform and prog ressively more numerous in the second and third instars. The dorsal sense o rgan is well defined in all three instars. The six oral ridges in the secon d and third instars are dentate ventrally. The life cycle is of the aggrega tive type. Most eggs are laid singly between the chaff and ovules of preblo ssom flower heads and perpendicular to the receptacle. First instars feed o n ovules, as do the second instars, which also feed on soft achenes in open flower heads, like all third instars. A third of the third instars examine d also pitted the receptacles and apparently supplemented their diet with s ap. Pupariation occurs inside the mature flower heads, but no protective ce ll is formed, as with congeners that overwinter as prepuparia. Instead, F-1 adults emerge from their cells in early summer (June) and either produce a partial second generation in late-blooming flower heads or pass the summer , fall, and winter in riparian habitats as long-lived adults. Surviving, ov erwintered adults aggregate the next year in early spring (March-April) on preblossom host plants to mate and subsequently oviposit. A Pteromalus sp. (Hymenoptera: Pteromalidae) was reared from puparia as a solitary, larval-p upal endoparasitoid.