Chlorfluazuron was applied to newly moulted fifth-instar larvae or .newly ecdysed pupae of the .common cutworm, Spodoptera litura (F.) by topical application. The values of LD50 and LD95 of pupae were higher than those of larvae. Sublethal doses (LD10: .1.00 ng/larva; 0.12 ng/female pupa;' 1.23ng/md.le pupa or L030: 3.75 ng/larva) were applied to females. and males and subsequent adults were mated in three different treatment combinations. First, treated females were mated with untreated males, for both doses (LD10♀x U♂; LD30♀x U♂) Secondly, untreated females were mated with treated males for both doses (U ♀x LD10♂; U♂ x LD30♂). Finally, treated both sexes were mated ,for both doses (LD10♀x LD10♂; LD30♀x LD30♂). The fecundity was reduced by 35 - 44% for all combinations of both doses. With both Sublethal. doses the fertility was reduced to 49 - 58% when females were treated, 65 - 81% when males were treated and 68 - 83% when both sexes were treated. The subsequent hatchability was reduced to 22 - 26% when females were treated, 44 - 66% when males were treated and 45 - 72% when both sexes were treated with both Sublethal doses. However,. there were no significant differences between larval and pupal treatments in the above mentioned parameters. .Moreover, there were no significant differences in daily patterns of them when compared with controls. The body weight reduction occurred during the development of larvae and pupae when treated with LD30 and in adults when. treated with LD10 or LD30. The duration of larval and pupal stages, the life-spans of male and female adults and the number of matings per pair remained unaffected by the larval or pupal treatments.
Sublethal doses of Chlorfluazuron significantly reduced ovarian weight and number of mature eggs in pupae and adults compared with controls, but their ratios were unaffected by the both treatments. In treated adults, the germarium was significantly longer than the pedicle and vitellarium, whereas in controls the vitellarium was significantly longer than the germarium and pedicle. The number of nuclei was also significantly reduced in the germarium. These results indicate delayed maturation of ovarioles in treated insects. These doses also disrupted growth and development of 06cytes by significantly affecting the size of basal oöcytes and the thickness of the follicular epithelium. The thickness of the follicular epithelium of basal oöcytes reached a maximum one day later in treated common cutworms. In newly emerged treated adults, the protein and nucleic acid (DNA and RNA) content of ovaries were significantly reduced, but the carbohydrate and lipid content were not significantly effected Ovarian ecdysteroid titres were low during pre-vitellogenesis, increased during vitellogenesis, peaked at the time of choriogenesis and decreased when insects started to deposit eggs and decreased thereafter. Ecdysteroid titres significantly decreased in LD10-, and ;more 'significantly decreased in LD30-treated females. However, the patterns of ecdysteroid titre secretion were the same as in controls.
Sublethal doses disrupted growth and development of the testes by decreasing the volume, weight and thickness of the sheath. The protein and nucleic acid (DNA and RNA) content were significantly reduced in the testes, but carbohydrate and lipid content were unaffected, Three peaks of testicular ecdysteroid were obtained during pupal development. The ecdysteroid titre was significantly reduced by Sublethal doses during larval, pupal and adult development.
Additionally, theses doses disrupted spermatogenesis by reducing the number and size of eupyrene and apyrene sperm bundles in the testes. Very few or no eupyrene sperm bundles were observed in the vas deferens of pre- and newly emerged adults. This shows that the transfer of sperm bundles from testis to vas deferens was delayed in treated males.
Male adults multiple-mated 10 times during the whole life-span of 13 days, when paired.each day with a new virgin female of the same age. A complete spermatophore was transferred through the male aedeagus and endophalus into the bursa copulatrix of the female after 50 min of copula formation. The number of inseminated eupyrene sperm decreased 66% or 88 %, respectively, in LD10 or LD30 treated males. However, no significant reduction in inseminated eupyrene sperm was observed when females were treated, The ratios .of eupyrene and apyrene sperm were unaffected, but the first mating was delayed by one day when males were treated with LD10 or LD30,
In addition, examination of the unhatched eggs revealed that the number of unfertilized eggs was greater than those that were fertilized. The greater number of unfertilized eggs was the result of treatments, The major; cause of failure in the number of hatchings was, therefore, a lack of fertilization, Interference by Chlorfluazuron, which was transferred by copulation through sperm fluids or ova, seems highly improbable. All these fertilized unhatched eggs in the treated crosses died. at an earlier stage than those of controls. In the female-treated crosses, the egg size was significantly reduced, compared with male-treated crosses. During mating, the treated males transferred significantly lower-weight spermatophores into the females.
In S. litura, two factors are involved in activation of oviposition. The first one obtained from virgin female haemolymph and the second one found in the haemolymph obtained from mated females. Sublethal doses of Chlorfluazuron significantly decreased their activities.