Catherine 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 .

Molting hormone titer changes and their significance during development of the colorado beetle, Leptinotarsa decemlineata

Abstract Molting hormone (MH) titer in whole animal extracts of Leptinotarsa decemlineata was determined by chemical extraction and the Musca test (1 MU = 3.5 ng ecdysterone) during the developmental span from newly-ecdysed fourth instar larva to an adult 3 days after eclosion. Within the 17-day period, 21 age groups were chosen to estimate the MH titer. Two peaks of MH titer were detected, one in the post-feeding larval stage and the other during the pupal and pharate adult stage. MH activity was first detected in 2-day-old post-feeding larvae, and reached a maximum of 23.5 MU/g tissue on the third day. It began to decline on 3.5 days, and fell to 5.5 MU/g tissue on 4.5 days, the time of larval-pupal ecdysis. In the pupal and pharate adult stage MH rose after the first day and increased to a maximum of 91.5 MU/g tissue on the third day. The titer again declined on the fourth day, and became undetectable one day before adult emergence and in adults 3 days after emergence. MH was demonstrated to be produced by isolated larval abdomens. A peak of 11.5 MU/g tissue was detected in 7-day post-ligation preparations. The titer decreased to 6.9 MU/g tissue in 10-day post-ligation preparations, which was the time of the ecdysis. The finding raises questions concerning the role of MH synthesis by other tissues in relation to the function of the prothoracic glands during insect development.

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.

Intergeneric Hybrids of Agropyron and Pseudoroegneria

Two intergeneric hybrids, Agropyron cristatum x Pseudoroegneria stipifolia (2n = 14) and A. desertorum x P. stipifolia (2n = 28), were produced by controlled pollination. Spike morphology of the hybrids was intermediate to that of the parents. Size differences between Agropyron (large) and Pseudoroegneria (small) mitotic chromosomes facilitated interpretation of chromosome pairing in the hybrids. Meiotic chromosome pairing in the diploid hybrids, x̄ = 3.09 II, was largely allosyndetic between homoeologous chromosomes of the S and the P genomes. Autosyndetic pairing prevailed in the tetraploid hybrids. Because the Agropyron chromosomes can pair with the Pseudoroegneria chromosomes, gene introgression between species in these two genera is possible.

Intergeneric hybrids and amphiploids between Pseudoroegneria spicata and critesion violaceum

Diploid (2n = 14) Pseudoroegneria spicata ssp. inermis (genome formula, SS; formerly in Agropyron) was hybridized with diploid (2n = 14) Critesion violaceum (genome formula, HH; formerly in Hordeum). The hybrids (genome formula, SH) were morphologically intermediate to the parents. Mean chromosome associations of 7.28I, 3.11II, 0.16III, and 0.05IV were observed at metaphase I in 208 cells from four hybrids. Of the bivalents, 90% were rod configurations leading to a mean chiasma per arm of 0.269. The hybrids were completely sterile. The SSHH amphiploid derivatives were morphologically like the FI hybrids and were partially fertile, averaging 2.6 seeds per spike. At metaphase I, the amphiploids averaged 4.01I, 11.37II, 0.26III, 0.09IV, and 0.03V in 160 cells. Many progeny of the amphiploids were natural outcrosses to other species growing in the same field nursery. At least nine outcross hybrids occurred with Agropyron cristatum (2n = 14; genome formula, PP) and even more with Critesion brevisubulatum (2n = 28; genome formula, HHHH). These two hybrid combinations, whose identities were established on morphological and cytological grounds, were also analyzed at metaphase I. Data from hybrids, C0 and C1 amphiploids, and outcross hybrids led to the conclusions that (1) the S, H, and P genomes are distinctly different but contain some residual homologies, and (2) SSHH amphiploids are segmental alloploids.

Feeding requirements and artificial diets for the alfalfa weevil

An artificial diet consisting of common nutritive substances was formulated for rearing the alfalfa weevil, Hypera postica (Gyllenhal). The palatability of this diet was enhanced by the addition of feeding stimulants identified during previous studies of this insect. The basal diet allowed 72% of newly hatched larvae to reach the adult stage. The addition of alfalfa leaf powders into the basal diet improved feeding and growth. The diet with 10% of acetone‐extracted leaf powder was most suitable, since the rate of development, pupal weight, and per cent adult yield of alfalfa weevils reared on this diet were almost identical to those reared on alfalfa leaves. The problem of developing an artificial diet for this oligophagous insect and the advantages of using artificial diets for laboratory rearing of the alfalfa weevil are discussed.

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.