Pyrazines as warning odour components in the Monarch butterfly, Danaus plexippus, and in moths of the genera Zygaena and Amata (Lepidoptera)

2-Methoxy-3-alkylpyrazines have been identified as odour components in Danaus plexippus, Zygaena lonicerae and an Australian Amata species, by means of coupled gas chromatography/mass spectrometry, with selected ion monitoring. Wide variability in pyrazine content was observed with D. plexippus and this was correlated with similar variability in the larval food-plants, Asclepias spp., which are presumed to be the odour sources for this butterfly. The importance of pyrazines in the biology of aposematic insects and their role as ingredients of a generalized warning system are discussed.     

The Effect of Hydroxymethanesulphonate on Photosynthesis in Chlorella pyrenoidosa

Photosynthesis under conditions known to favour glycollate excretionby algae did not result in glycollate excretion in a strainof Chlorella pyrenoidosa unless an inhibitor of glycollate oxidase,-hydroxypyridin-2yl-methane sulphonate (-HPMS), was present.This inhibitor increased the total amount of glycollate presentin the supernatant from the cells during photosynthetic carbondioxide fixation and gave accumulation of ¹⁴C in glycollateduring ¹⁴CO₂ fixation under conditions favouring glycollatesynthesis. At pH 8.3 -HPMS did not stimulate photosynthetic¹⁴CO₂ fixation in C. pyrenoidosa as occurs with some algae.Photoassimilation of acetate was inhibited by -HPMS, and thiswas shown to result from acetyl-CoA synthetase inhibition by-HPMS.     

COMPARISON OF RAPID TECHNIQUES FOR THE DETECTION OF ESCHERICHIA COLI O157:H7

Four different commercial kits (EHEC-TEK of Organon Teknika, Durham, NC; HEC O157 of 3M, St. Paul, MN; and Coline dipstick and Coline one-step of AMP-COR Inc., Camden, NJ) were evaluated for the detection and recovery of E. coli O157:H7from 75 fresh meat samples and 23 artificially inoculated beef and pork samples. Of the total 75 samples tested, 21 (28%) were presumptive positive by HEC O157 and Coline dipstick, 18 (24%) by Coline one-step, and 12 (16%) by EHEC-TEK. None of the presumptive positive samples by any of the methods was confirmed as E. coli O157:H7 (false positive). Of the 23 positive spiked samples tested, 23 were recovered by Coline dipstick and one-step (100%), 22 (95.6%) by HEC O157, and 20 (86.9) were recovered by EHEC-TEK. In the confirmation step 17 of the 23 spiked samples produced characteristic colonies on MacConkey sorbitol agar (Difco) with 5-bromo-4-chloro-3-indoxy-β-D-glucuronide (Biosynth International) (MSA-BCIG) and were confirmed as E. coli O157:H7. No characteristic colonies on MSA-BCIG were detected for 6 of the spiked samples with initial inoculum levels of between 2 to 70 cells/g and, therefore, were not confirmed as E. coli O157:H7. A better enrichment medium, as well as improved selective plating and confirmation techniques, are needed to enhance the selective growth of E. coli O157:H7 and provide lower detection levels.     

Uptake and Movement of 14C-Chlormequat Chloride Applied to Leaves of Barley and Wheat

Chlormequat chloride labelled with ¹⁴C was applied to the thirdleaf of Proctor barley and Maris Dove wheat; after 1 d lessthan a fifth could be washed off with water. More ¹⁴C-labelledmaterial moved from treated areas of wheat than of barley toaccumulate in tips of treated leaves, younger main-stem leaves,main stems, and ears. Relatively small amounts of radioactivematerial accumulated in roots, but less in wheat than barley.About 80% of the radioactivity was recovered from plants upto 1 week after application, but the amounts recovered in aqueouswashings and extracts decreased faster from wheat than frombarley.     

Differences in the mating behaviour of the rat flea Nosopsyllus fasciatus (Bosc)

An account is given of differences in development at emergence in two strains of Nosopsyllus fasciatus, and of consequent differences in mating behaviour.