A post‐feeding diuretic response has been observed in adult Heliothis zea (Boddie) (Lepidoptera: Noctuidae). 2‐day‐old starved adults which were allowed to feed to repletion on a 10% (w/v) sucrose solution lost 49.1% (females) and 85.8% (males) of the weight of the ingested meal during the first hour following feeding. Ligation between head and thorax or frontal ganglionectomy, when performed immediately following feeding, each resulted in a significant and permanent reduction in this normal weight‐loss. Injection of homogenates of the corpora cardiaca/corpora allata (CC/CA) complex into non‐ligated insects immediately after feeding also reduced significantly the post‐feeding weight‐loss, but this inhibition was transient and disappeared after 1 h. Dissection and weighing of the crop from either ligated, frontal ganglionectomized, or CC/CA‐injected insects confirmed the crop as the predominant site of fluid retention in each case. We suggest that a soluble antidiuretic factor from the CC/CA acts in conjunction with the frontal ganglion to control the rate of crop emptying and subsequent diuresis by regulating the volume of ingested fluid that is passed into the haemolymph from the crop/midgut.

We describe an undergraduate laboratory experiment in protein gel electrophoresis that uses readily available apparatus and materials. The separation of a mixture of stained proteins by gel electrophoresis was videotaped. Position–time data for the proteins generated from analysis of digitized videotape images allowed for calculation of protein terminal velocities. The dependence of protein terminal velocity on molar mass was determined and found to agree with predictions made by current theory. We also introduce a model that draws on simple physical concepts to help students place the experimental results in context.

ABSTRACT. The marked weight loss that follows adult eclosion in Heliothis zea (Boddie) (Lepidoptera: Noctuidae) was found to be the result of diuresis. This diuretic weight loss amounted to 18.2% of the emergence weight in females and 22.5% in males. Ligation between head and thorax immediately following emergence resulted in a significant reduction in this weight loss. Injection of homogenates of brain (BR) or suboesophageal ganglion (SOG) partially restored the weight loss in ligated insects, indicating potential neurohormonal regulation of this phenomenon. Because injection of homogenates of nervous and neuroendocrine tissues other than BR and SOG did not result in increased weight loss over controls, the activity present in BR and SOG was probably a tissue‐specific phenomenon. We speculate that a factor at least partially responsible for the enhanced diuretic weight loss is present in the fused BR/SOG.

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