Reactions of immature stages of noctuid moths to juvenoids

Abstract

Acetone solutions containing 0.01% or more of juvenoids inhibit hatching when administered to freshly laid eggs of Spodoptera littoralis and Mamestra brassicae. Application of 1–100 μg of juvenoids to penultimate instar larvae of these species induces light body coloration in the last instar larvae. The effect on body coloration, however, is ambiguous in Autographa gamma. Metamorphosis is most readily inhibited by administering juvenoids within the second half of the feeding period in the last larval instar and at the start of the pupal instar. The isopropyl 11‐methoxy‐3,7,11‐trimethyl‐2,4‐dodecadienoate was the most active compound out of 32 juvenoids examined. It affected A. gamma at 0.05 μg, S. littoralis at 0.8 μg, M. brassicae at 6 μg, and Scotia ipsilon at 50 μg per specimen. The treated larvae either grow much bigger than the controls, rarely undergo an extra larval moult, and eventually they produce giant pupae (often inviable); or they develop into intermediate forms showing species specific distribution of larval and pupal features. These observations complemented with other evidence suggest that the juvenile hormone normally is involved in induction of the solitary phase in the development of certain lepidopterans as well as in the control of the length of the last larval instar and of the body size which the larvae attain before pupation. Zusammenfassung Reaktionen der Eier, Raupen und Puppen von Eulen (Noctuidae) auf Juvenoide Versuche mit 0,01‐ bis 1%igen Acetonlösungen von 32 ausgewählten Juvenoidverbindungen bei frisch abgelegten Eiern von Mamestra brassicae und Spodoptera littoralis zeigten, daß 28 dieser Substanzen das Eischlüpfen verhinderten. Ein allgemeiner Zusammenhang zwischen der chemischen Struktur und der oviziden Wirkung konnte nicht festgestellt werden. Die mit 1–100 μg einiger Juvenoide behandelten Raupen des vorletzten Larvenstadiums färbten sich im letzten Stadium hell (solitäre Färbung). Diese Wirkung auf die Larvenpigmentierung war nicht eindeutig bei Autographa gamma. Die Verpuppung der behandelten Raupen aller untersuchten Arten (einschließlich Scotia ipsilon) wurde verzögert und die entstandenen Puppen wogen wesentlich mehr als die Kontrollen. Diese Resultate weisen auf die wichtige Rolle des Juvenilhormons bei der Steuerung des Phasenwechsels, der Entwicklungslänge und des Wachstumsumfangs im letzten Larvenstadium hin. Die mit höheren Mengen der Juvenoide behandelten Raupen wandelten sich nicht zu Puppen, sondern entweder zu Riesenraupen (im Falle von S. ipsilon und S. littoralis) oder zu larval‐pupalen Mischformen (bei allen Arten). Die Verteilung der larvalen und pupalen Cuticula in diesen Übergangsformen erwies, daß das raumzeitliche Muster der pupalen Differenzierung der Epidermis artspezifisch ist. Bei S. ipsilon, M. brassicae und S. littoralis kamen auch intermediäte Typen zwischen der larvalen und pupalen Cuticula vor. Die morphogenetische Wirksamkeit der Juvenoide wurde an den Raupen des zweiten Drittels des letzten Stadiums getestet. Die höchstaktive Substanz...

Effects of nonsteroidal ecdysone agonist RH-5992 and chitin biosynthesis inhibitor lufenuron on Spodoptera littoralis (Boisduval, 1833)

“…Procedures for the rearing of the moth were described in detail by Sehnal et al [20]. Eggs, larvae and adults were used in our experiments.…”

SILENCING THE EGYPTIAN COTTON LEAFWORM; Spodoptera littoralis (BIOSD.) CYTOCHROME P450 INHIBITS THE METABOLISM OF GOSSYPOL USING RNAI TECHNIQUE

“…strain was reared at 25±1°C with 70-80% relative humidity under a L16: D8 photoperiod in the laboratory. This strain was reared for more than 12 subsequent generations under above conditions as described by Sehnal et al, (1976).…”

Moulting, growth and survival of Galleria mellonella L. (Lep., Pyralidae) treated with juvenoids

“…Inhibition of metamorphosis and induction of surplus larval development by juvenoids is accompanied by acceleration of moulting (SLAMA et al 1974). O n the other hand, low and moderate doses of juvenoids, which fail to elicit a morphological effect, often cause a considerable prolongation of the last larval instar of Holometabola (SEHNAL 1976). These observations led SLAMA (1975) to conclude that juvenoids interfere with ,,the hysiological programming of the secretory functions of the prothoracis glan s s." Several authors (NIJHOUT and WILLIAMS 1974;CHIPPENDALE 1977;TAKEDA 1978) suggested that the delay of moult is due to inhibitory action of juvenoids on the brain.…”

“…Juvenoids applied to caterpillars frequently extend the period of larval growth (BRIEGER 1973;PLANTEVIN 1975;SILHACEK and OBERLANDER 1975;KRYSPIN et al 1977;SEHNAL et al 1976). Prolongation of larval feeding has a great practical significance because increased food consum tion would hamper the use of juvenoids against many insect pests.…”