Journal of Insect Physiology 44 (1998) 1111–1117 Temporal profiles of juvenile hormone titers and egg production in virgin and mated females of Heliothis virescens (Noctuidae) Shengqiang Shu a,c , Yong Ihl Park a , Sonny B. Ramaswamy a,c,* , Asoka Srinivasan b a Department of Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762-9775 USA b Department of Biology, Tougaloo College, Jackson, MS 39714 USA c Current address: Department of Entomology, 123 Waters Hall, Kansas State University, Manhattan, KS 66506-4004 USA Received 14 April 1997; received in revised form 14 August 1997 Abstract Juvenile hormones (JH) I, II, and III were monitored in hemolymph of virgin and mated females of various ages in Heliothis virescens. JH I was the predominant homologue followed by JH II, but JH II was present at a higher level in young virgin females. JH III was detectable only at a low level. In virgin females, hemolymph JH titers were low at emergence (2.2 ng/ml-total amount of JH I and JH II), but increased thereafter and reached a maximum at 24 h of age (53.5 ng/ml). At 30 h and 36 h of age, JH titers dropped to a low level, but increased again in older virgin females. After mating, JH titers increased significantly. JH titers at 0 h after uncoupling (137.4 ng/ml) were nearly 3 times as high as those in 24-h-old virgin females. Within 6 h after uncoupling, JH titers decreased slightly, but titers increased with age of mated females and reached a level of 320.2 ng/ml hemolymph at 72 h after uncoupling. The titer of JH I and JH II was correlated highly with total number of eggs produced (r 2 = 0.70, P  0.001). Mating stimulated JH production, resulting in an increase in egg production.  1998 Elsevier Science Ltd. All rights reserved. Keywords: Oogenesis; JH; GC-MS; Methoxyhydrin; Lepidoptera; Noctuidae; Tobacco budworm 1. Introduction The role of juvenile hormone (JH) in egg development and/or maturation in Lepidoptera has been established for species such as Danaus plexippus, Diatraea grandi- osella, Helicoverpa zea, Heliothis virescens, Manduca sexta, Nymphalis antiopa, Polygonia c-aureaum, Pieris brassicae, Pseudaletia unipuncta, and Vanessa cardui among others [see references in Ramaswamy et al. (1997)]. However, the dynamics of JH titers and egg development are poorly understood in lepidopterans because data on in vivo JH titers are scant. The reasons for the lack of data are numerous, not the least of which is the difficulty in the precise and specific measurement of JH titers. Several authors have measured the ability of corpora allata (CA) from adult lepidopterans to syn- thesize and release JH in vitro. However, CA activity does not necessarily reflect hormonal events in vivo, * Corresponding author. Tel: (785) 532-6154. Fax: (785) 532-6232. Email: RSONNY@KSU.EDU 0022–1910 /98 /$19.00  1998 Elsevier Science Ltd. All rights reserved. PII:S0022-1910(97)00117-0 because hemolymph titers are the result of synthesis, release, and degradation. The physico-chemical method developed by Bergot et al. (1981) has been employed to achieve precision and specificity of JH titer measure- ments. In vivo JH titers in adults have been documented for only three lepidopteran species (Lessman et al., 1989; Edwards et al., 1995; Shu et al., 1997). Females of many insect species stop developing new oocytes if they remain virgin. In species requiring JH for oocyte development and maturation, this cessation in egg development was attributed to low JH titers. Based on the decreasing rate of egg maturation in virgin females from 3.2 eggs/hour to 0.5 eggs/hour at 48 h after eclosion, Nijhout and Riddiford (1974) inferred that CA in M. sexta continued to release JH for only two days in virgin females and then apparently ceased JH release. Upon mating, the rate of egg maturation showed a resurgence, which was interpreted to be a result of reacti- vation of the female’s CA and its concomitant effects on egg development (Sasaki and Riddiford, 1984). One study on JH titers in a noctuid adult, Lacanobia oleracea (L.), supports the above conjecture. In vivo JH titers in