Biology of a tydeid mite,Homeopronematus anconai(n. comb.) (Acari: Tydeidae), important in San Joaquin Valley vineyards

Abstract

1943), new combination, is reviewed, and Homeopronematus vidae And& I 9 8 0 is designated a new synonym. The tydeid mite H. anconai has an egg, one larval, and three nymphal stages. Each postlarval stage begins with a prolonged period of quiescence following apolysis and preceding ecdysis. Quiescent phases are approximately as long as active immature phases. After adult female ecdysis, there is a short preoviposition period followed by a long reproductive period, during which up to 66 eggs per female are laid. When ample food is present, most of the eggs are laid early in the reproductive period. Mean generation time (T) is 2 0. 6 days at 2 4 "C and 11.8 days at 3 0 "C. Reproduction is arrhenotokous: unmated females produce male offspring only. The sex ratio is female-biased. An overall estimate of sex ratio is 2. 2 females per male. These mites have a clumped distribution in laboratory colonies. Quiescent stages, exuviae, and active larvae and adults are often aggregated near some physical feature such as a leaf vein or cotton strand, but aggregations also occur on otherwise apparently featureless leaf surfaces. Hungry H. anconai females spend more time on leaf surfaces with residues left by other H. anconai females, suggesting that tactile andlor chemical cues produced by the mites themselves may be partly responsible for the aggregation behavior. Female H. anconai have a photoperiodically induced, temperature-sensitive hibernal reproductive diapause. Diapausing females are mated but nongravid and are morphologically distinguishable in Continued inside back cover.

Mating behavior in the tydeid miteHomeopronematus anconai (Acari: Tydeidae)

“…The genital aperture is more posteriorly located in males and has one, rather than four, aggenital setae (Andre, 1980). The male has a Yshaped aedaegus (Knop and Hoy, 1983), similar to that described by Schruft (1972) for Homeopronematus (Pronematus) staerki (Schruft). Males have dorsal lateral "rosettes", which are circular cuticular patterns on the hysterosoma (Baker, 1968), and a distinctive "hook" on femur IV (the "spur" of Baker (1968) and Schruft (1972), "dorsal excrescence" of Andr~ (1979)).…”

“…C. malaccensis exhibits "nesting behavior" , T. urticae has a highly clustered distribution, especially at low densities (Rabbinge and Hoy, 1980), and H. anconai tends to be aggregated particularly during pharate phases (Knop and Hoy, 1983). All three species are arrhenotokous and have a female biased sex ratio.…”

“…The developmental stages of H. anconai include egg, an active larval, and three nymphal stages (Knop and Hoy, 1983). Since each post-larval stage begins with an immobile pharate phase following apolysis but preceding ecdysis, it was possible to secure virgin adult females by isolating them while pharate.…”

“…Striations which cover the rest of the body disappear in these areas, although the cuticular lobes do not. When specimens mounted in Hoyer's medium (Krantz, 1978) are examined by phase contrast microscopy the "rosettes" appear as dark disks (Knop and Hoy, 1983). Similar structures in other tydeid males are thought to be muscle attachment sites, or sigilla (Baker, 1965;Andre, 1981a).…”

“…3). After a pre-oviposition period of 2.2 days at 24~ (Knop and Hoy, 1983), females begin to lay eggs whether or not they are mated. Virgin females that were provided with males from just after they laid their first eggs until the end of their lives never produced female offspring (Fig.…”