T. H. Hsiao

Simultaneous determination of molting and juvenile hormone titers of the greater wax moth.

Abstract A simple and rapid extraction procedure was developed to determine simultaneously the molting hormone (MH) and juvenile hormone (JH) activity in a single insect tissue sample. From the onset of the last larval stage to adult eclosion of the greater wax moth, Galleria mellonella, three JH peaks were noted: at the time of the sixth larval ecdysis, 1 day before the seventh larval ecdysis, and at the time of adult eclosion. Three MH peaks were recorded for the male: at 1 day before the sixth larval ecdysis, 1 day before the seventh larval ecdysis, and 2 days after pupation. In the female, a fourth peak was shown at the time of adult eclosion. This fourth peak exhibits the highest molting hormone activity of all samples, 1600 Musca units/g of fresh tissue or an equivalent of 5.6 μg/g of ecdysterone. Eighty per cent of this MH accumulated in the ovary. The significance of MH and JH titers as related to the endocrine regulation of development is discussed in the light of this finding.

Ecdysteroids in the ovary and the egg of the greater wax moth

Abstract Galleria mellonella eggs exhibit a remarkably high molting hormone activity, equivalent to 74 μg/g fresh wt of ecdysone or ecdysterone. The activity in the ovary was also substantial, averaging 0.4 and 0.58 μg/female, respectively, in the pharate adults and in the 1-day-old adults. Seven ecdysteroids were isolated from the eggs. Ecdysone and ecdysterone were the principal components, comprising 80% of the total biological activity, followed by their 3-epimers and three unidentified ecdysteroids with less biological activity. Five of the seven ecdysteroids were found in the ovaries of the pharate adults and six in the 1-day-old adults. In both the ovary and the egg, 80–85% of these ecdysteroids existed in the conjugated form, mainly as sulphates, and were partitioned in both the n -butanol and the water phases. The ratio of these ecdysteroids changed significantly from the ovary to the egg, with ecdysone decreasing, ecdysterone increasing, and the others increasing slightly. The results suggest that these ecdysteroids exist in a dynamic state and are not merely inactivation products or storage forms.

Insect hormones: Their effects on diapause and development of hymenoptera

Abstract Prepupal diapause of the alkali bee, Nomia melanderi , was terminated by injection of ∝-ecdysone and three phytoecdysones (cyasterone, ecdysterone and inokosterone). Synthetic juvenile hormone, cholesterol, β-sitosterol, copper sulfate and zinc acetate had no effect. When juvenile hormone was injected simultaneously with ∝-ecdysone, the diapausing prepupae molted into normal pupae, but later developed into pupal-adult intermediates. ∝-Edysone also terminated the larval diapause of the leaf-cutter bee, Megachile rotundata .

Hybridization and cytoplasmic incompatibility among alfalfa weevil strains

Cross‐matings were conducted among eastern, western, and Egyptian alfalfa weevil strains. Fully viable progenies were produced in reciprocal crosses between eastern and Egyptian weevils. The cross between western males and females of eastern or Egyptian strains was incompatible, producing infertile eggs, while the reciprocal cross yielded viable progeny but with a distorted sex ratio, predominantly female. The cause of incompatibility is due to the presence in the western weevil of a rickettsia, which is transmitted through the female parent. Of eight weevil populations surveyed, only the western weevil and a weevil population from the Netherlands harbored the rickettsiae. We conclude that all alfalfa weevil populations in the United States belong to the same species, Hypera postica (Gyllenhal), and that they are potentially interbreeding populations.

Discrimination of alfalfa weevil strains by allozyme analysis

Allozyme profiles of eastern weevils (Beltsville, Maryland; Washington Co., Illinois), western weevils (Logan and St. George, Utah), and Egyptian weevils (Yuma, Arizona; Westmorland, California) were compiled by acrylamide gel electrophoresis. Twenty‐two gene loci from 12 enzymes (ACPH, ADH, AMY, AO, EST, GOT, G‐6PDH, MDH, ME, SOD, TYR, XDH) were analyzed. Mean heterozygosity of these populations was 0.231, with an average proportion of polymorphic loci of 0.536. The mean genetic distance of all weevil populations was 0.033 and the fixation index was 0.024. Diagnostic loci were found which could distinguish western weevils from eastern and Egyptian weevils. The small genetic distance between the eastern and Egyptian weevils suggests that they may be the same strain and are certainly different from the western weevil strain. Based on this and other evidence, we conclude that all weevil strains in the United States are Hypera postica (Gyllenhal), and that the use of H. brunneipennis (Boheman) for the Egyptian alfalfa weevil of North America should be discontinued.

Characterization of a protein toxin from dried specimens of the garden tiger moth (Arctia caja L.)

Abstract A protein toxin was isolated from the female abdomen of dried specimens of the garden tiger moth, Arctia caja L. It is toxic to both the house fly and the white mouse. The toxin is labile to heat (60°C) and organic solvents; is unstable to low pH and freeze-drying; and is destroyed by proteolytic enzymes. Purification by molecular sieve and ion exchange Sephadex column chromatography showed that the toxin has a mol. wt of about 50,000. In polyacrylamide gel disc electrophoresis, it has an Rf value of 0·4. The protein toxin has an isoelectric point of 6·0 as determined by isoelectrofocusing. The toxic symptom of the protein toxin to white mice is similar to that of the small mol. wt polypeptide previously isolated from fresh specimens by Rothschild et al. (1979), but the latter toxin was not found in a detectable amount in the dried specimens used in this study. This protein toxin resembles chemically the neurotoxin, leptinotarsin, from the Leptinotarsa species, but apparently has a quite different mode of action on both insects and mammals.

Inheritance of a vestigial wing mutation in the alfalfa weevil, Hypera postica

Alfalfa weevils (Hypera postica (Gyllenhal)) with vestigial hind wings were discovered in a population from Wageningen, the Netherlands, and two populations from the United States – an eastern weevil strain from Beltsville, Maryland and an Egyptian weevil strain from Atascadero, California. Such a mutant was absent from 23 other populations surveyed in the United States – three from eastern, seven from western, and 13 from Egyptian weevil strains. This mutation is due to a dominant autosomal gene with normal‐wing individuals as recessive. The mutant gene can be transferred from eastern weevil to the western weevil strain. The short‐wing trait may be useful for genetic manipulation to control the alfalfa weevil.