Dimethyl 1-dodecanephosphonate has been shown in laboratory bioassays and greenhouse tests to be highly active against 2 species of nematodes. Other phosphonate esters showed little or no activity.

Thirteen secondary and tertiary amides and amines that disrupt growth and development in certain insects were tested at concentrations of 0.25–5.0 p.p.m. for their effects on development of Ostertagia ostertagi , from infective larvae to egg-laying adults, in a two-step roller culture system. These compounds did not affect exsheathment of infective larvae. However, some of these compounds inhibited development or killed 100% of the exsheathed larvae at concentrations of 1.0–2.5 p.p.m. Minimum inhibitive concentrations of several of the amines and amides affected the nematodes in one or more of the following ways: decreased motility or paralysis; reduced survival; delayed or blocked third or fourth ecdysis; lowered yields of advanced stages; decreased production of fertile and non-fertile eggs. The results also indicated that, as in insects, these chemicals exerted their lethal effects against O. ostertagi at the time of molt.

Metabolic studies in which3H-sitosterol,3H-stigmasterol, and14C-desmosterol were administered by feeding and injection to the khapra beetle,Trogoderma granarium Everts, provided strong evidence that this insect is unable to dealkylate phytosterols and convert them to cholesterol.

The khapra beetle,Trogoderma granarium Everts, does not dealkylate and convert dietary C28- or C29-phytostorols to C 2T sterols such as cholesterol. There is, however, an increase in the concentration of cholesterol and campesterol in its tissues relative to the dietary concentrations of these sterols, presumably as a result of selective uptake.

Journal Article Design of Some Delayed-Action Toxicants for Baits to Control Red Imported Fire Ants Get access J. P. Kochansky, J. P. Kochansky Search for other works by this author on: Oxford Academic PubMed Google Scholar W. E. Robbins, W. E. Robbins Search for other works by this author on: Oxford Academic PubMed Google Scholar C. S. Lofgren, C. S. Lofgren Search for other works by this author on: Oxford Academic PubMed Google Scholar D. F. Williams D. F. Williams Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Economic Entomology, Volume 72, Issue 5, 1 October 1979, Pages 655–658, https://doi.org/10.1093/jee/72.5.655 Published: 01 October 1979 Article history Received: 19 April 1979 Published: 01 October 1979

The sterols of a phytophagous and a predacious species of the family Coccinellidae were found to be quite different from each other, indicating that adaptation to different diet regimens is reflected in the utilization and metabolism of dietary sterols.

Insects are unable to biosynthesize the steroid nucleus and generally require an exogenous source of sterols. Two salient areas of insect steroid metabolism are the dealkylation and conversion of dietary C28 and C29 plant sterols to cholesterol and other C27 sterols, and the biosynthesis and metabolism of the steroidal insect molting hormones. Certain azasteroids and nonsteroidal amines block this conversion of 24-alkyl sterols to cholesterol and/or disrupt molting and development in insects. These inhibitors have served in charting metabolic pathways for steroids in insects and are serving as models in developing selective pesticidal chemicals and chemotherapeutic agents for use against insects and other invertebrate pests and parasites. The mode of action of some of these inhibitors on molting and development has been investigated in vivo and in vitro. Certain of these inhibitors represent a new class of insect hormonal compounds with a novel mode of action-the disruption of molting hormone metabolism. Research on sterol metabolism in insects provides important information on the comparative biochemistry and physiological functions of steroids in living systems.

Analysis of the sterols of the milkweed bug, Oncopeltus fasciatus (Dallas) and dietary sunflowerseeds revealed that there is little, if any, conversion of dietary C28 OR C29 phytosterols to cholesterol in this phytophagous insect. The dietary sterols are apparently utilized with little alteration both during development to the adult stage and egg production, and cholesterol comprises less than 1% of the sterols in either adult males and females or in the eggs. The significance of these findings are discussed in light of the recent discovery that the C28-ecdysone, makisterone A, is the predominant molting hormone inthe embryonated egg of the milkweed bug.

26-Hydroxyecdysone is the predominant molting hormone in 24- to 44-hour-old embryonated tobacco hornworm eggs, accounting for approximately 80% of the ecdysones present at this stage of development. This molting hormone was previously shown to be the major ecdysone present in 48- to 64-hour-old embryonated eggs of this insect. During both of these periods of embryonic development in the hornworm 20-hydroxyecdysone is a minor component, in contrast to its presence as the major ecdysone in the hornworm during certain stages of post-embryonic development.