Life history and description of miniature stages of Oxyna aterrima (Doane) (Diptera: Tephritidae) on Artemisia tridentata Nuttall (Asteraceae) in southern California

Oxyna aterrima (Doane) is a univoltine, monophagous, circumnatal tephritid reproducing in galls of terminal and axillary buds on terminal branches of Artemisia tridentata Nuttall. The first-, second-, and third-instar larvae, and puparia are described and figured. Oxyna utahensis Quisenberry is synonymized with O. aterrima on the basis of morphology and concurrent rearings of flies that would key to both names from the same type of galls on the same host-plant individuals. The third instar of O. aterrima is distinguished from other known Tephritinae by the verruciform sensilla surrounding each posterior spiracular plate dorsolaterally, laterally, and ventrolaterally, and by the pair of verruciform sensilla comprising each intermediate sensory complex. Oviposition occurs in spring (May-June) and the first instars pass the Summer (June-September) singly in small, basal, ovoidal cells within the slow-growing, small, clavoidal, uniloculate, bud gall. Second instars occupy their still-small chambers until early winter (December), when they L molt to third instars, that then overwinter and grow slowly until the resumption of the spring flush of new plant growth (March). At this time, the third instar enlarges the gall chamber within the still-small gall to accommodate its faster growth and fashions an apical or subapical window for adult egress. During larval growth and development the gall apparently serves as a plant nutrient-sink to which the largely liquid diet of the larva is translocated. Pupariation follows in early April, and adults emerge by mid-April. Adults on average are short-lived (ca. 2-3 weeks). Mating behavior is described. Mesopolobus sp. and Pteromalus sp. (Hymenoptera: Pteromalidae) and a single individual of Eupelmus sp. (Hymenoptera: Eupelmidae) were individually reared from third instars or puparia of O. aterrima as solitary, larval and/or pupal ectoparasitoids. Predation by birds, probably bushtits, Psaltriparus sp., also is reported.