Oviposition Behaviors and Ontogenetic Embryonic Characteristics of the Western Tarnished Plant Bug,Lygus hesperus

Abstract

The western tarnished plant bug, Lygus hesperus Knight (Hemiptera: Miridae) is a key pest of fruit, vegetable, and field crops in the western United States, but many aspects of L. hesperus ecology are poorly documented. A sound understanding of oviposition behavior and characterization of the phases of embryonic development would be useful in studies of interactions between L. hesperus and its hosts, and in efforts to better understand the developmental consequences of low temperatures. Because L. hesperus insert their eggs into the host, most of the egg is obscured from view, and some aspects of oviposition and subsequent egg development cannot be observed directly. A novel observational method which took advantage of the propensity for L. hesperus to oviposit in semi-transparent sheets of agarose was used to observe oviposition and subsequent embryonic development. Lygus hesperus females stylet-probed prospective oviposition sites and during oviposition the ovipositor followed the path of the final probe. Oviposition, from insertion to withdrawal of the ovipositor, required ∼30 seconds. Identifiable phases of embryo development included egg swelling, katatrepsis, appearance of body segments and appendages, development of red pigmentation in the eyes and terminal antennal segments, and formation of the 3rd embryonic cuticle. These phases were observed at about 0.3, 0.4, 0.5, 0.6, and 0.8 of the total duration between oviposition and hatch, respectively. Infertile eggs did not exhibit any of these phases. Our descriptions of embryonic development will facilitate the study of L. hesperus egg biology and ecology, and permit estimates of egg population age structure and prediction of egg hatch.

Temperature-Dependent Egg Development of <I>Lygus hesperus</I> (Hemiptera: Miridae)

“…Eggs oviposited in agarose were obtained using the methods described by Cooper and Spurgeon (2012a). Two 12-well tissue culture dishes without lids (product number 352043, BD Falcon, San Jose, CA) were stacked with the upper dish inverted over the lower dish so that the wells of the two plates adjoined.…”

“…Mortality of eggs oviposited in agarose was identiÞed by a change in egg color from yellow or amber to white. Appearance of red pigmentation on the distal antennal segments and the eyes represents a phase of L. hesperus embryonic development that can be observed through semitransparent agarose (Cooper and Spurgeon 2012a). Therefore, eggs oviposited in agarose also were examined for the development of red pigmentation.…”

“…Studies of the development of endophytic eggs such as those of Lygus spp. are difÞcult near the lower developmental threshold because the oviposition substrates commonly used in laboratory studies may deteriorate and destroy the eggs before embryonic development is complete (Cooper and Spurgeon 2012a). Champlain and Butler (1967) interpreted the failure of L. hesperus eggs to hatch at temperatures below 12.8ЊC as lack of Mention of trade names or commercial products in this article is solely for the purpose of providing speciÞc information and does not imply recommendation or endorsement by the United States Department of Agriculture.…”

“…Separation of the chorion and operculum of eggs held at 10ЊC was observed in preliminary studies of L. hesperus egg development (W.R.C., unpublished data). The observed separation of the chorion and operculum indicated that at least the initial phases of embryonic development had occurred (Cooper and Spurgeon 2012a). Cooper and Spurgeon (2012a) determined that L. hesperus females would oviposit in semitransparent agarose and that the agarose was less subject to deterioration than were natural oviposition substrates.…”

“…Cooper and Spurgeon (2012a) determined that L. hesperus females would oviposit in semitransparent agarose and that the agarose was less subject to deterioration than were natural oviposition substrates. Use of semitransparent agarose substrate also allows the observation of early phases of embryonic development that are obscured when eggs are deposited in plant material (Cooper and Spurgeon 2012a).…”