Charles H. Schaefer

Changes in the composition of lipids and fatty acids in adult Culex tarsalis and Anopheles freeborni during the overwintering period

Abstract Anopheles freeborni adults are heaviest and contain their highest lipid content at the initial part of the overwintering period. Their lipid and fatty acid content decline steadily during the overwintering months. Culex tarsalis adults have the same approximate amount of lipids and fatty acids at the beginning as at the end of the overwintering period but have about twice that amount at the mid-part of the same period. Thus, C. tarsalis reaches its maximum lipid content much later than does A. freeborni . Both species utilize their major fatty acid (C 16 : 1) to a much larger extent than other fatty acids.

Synthesis of energy for overwintering in natural populations of the mosquito Culex tarsalis

Abstract 1. 1. Overwintering Culex tarsalis adults synthesized lipids during October and early November 1968 in the Sacramento Valley of California. Approximately 78 per cent of the total lipids are triglycerides, which are the main store of energy for overwintering. 2. 2. About 15 per cent of the total lipids separated with the free fatty acid fraction. 3. 3. The fatty acids of the triglyceride fraction are almost entirely composed of compounds commonly encountered in insect tissues, while five unknown compounds account for over 15 per cent of the free fatty acid fraction.

The accumulation and elimination of diflubenzuron by fish

In summary, diflubenzuron is accumulated from water into fish tissues at levels up to 80 fold within 24 hr when fish are exposed to concentrations of 10 ppb. Within the concentration range of 1-10 ppb, the amount accumulated in a 24 hr exposure is proportional to concentration. After 24 to 48 hr exposure fish degrade and eliminate diflubenzuron and the excretory products are neither the parent compound nor p-chlorophenylurea. The amount of diflubenzuron remaining in fish tissues with time is dependent on the reduction of residue concentration in water; however, the potential for degradation and elimination is very great.

Sources of energy utilized by natural populations of the mosquito, Culex tarsalis, for overwintering

During the fall and winter Culex tarsalis adults feed on sugars, presumably from plants, which they utilize for the synthesis of triglycerides and perhaps directly. Glucose and fructose are the predominant compounds identified in crop liquids, but melezitose sometimes accounts for about one-third of the total sugars and trehalose and raffinose frequently account for about 5 to 10 per cent. The usual absence of sucrose in the crop sugars may largely be due to the action of salivary enzymes which readily cleave it to monosaccharides. Trehalose and raffinose are relatively stable to the action of the salivary enzymes, but melezitose is slowly cleaved to monosaccharides. In laboratory cage experiments C. tarsalis females obtained sugars from the flowers of weeds as well as from other plant sources which were offered, e.g. sugar beet tubers and raisins; thus, this mosquito appears to be able to obtain energy from a wide variety of sources.

Studies on the environmental persistence of S-31183 (pyriproxyfen): Adsorption onto organic matter and potential for leaching through soil

Analytical methods were developed to allow the extraction and analysis of S-31183 (pyriproxyfen), 2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]pyridine, in organic matter from animal waste-water lagoons. Analysis of water and organic debris from a treated lagoon showed that the active ingredient readily adsorbed onto organic matter. S-31183 persisted on organic matter for over a 2-month period, during which time the concentration decayed at an exponential rate. In leaching trials with four different soil types, over 50% of the active ingredient applied remained in the upper 6 cm of a 30-cm soil column; there was no indication of a rapid potential for downward migration. The use of S-31183 for treating wastewater lagoons at doses which are effective for mosquito control did not result in any apparent problems of environmental incompatibility.

Studies on the mode of action of the chemosterilants 2-imidazolidinone and 4-imidazolin-2-one in the house fly and in the large milkweed bug

Abstract 2-Imidazolidinone and 4-imidazolin-2-one are temporary sterilants in house flies ( Musca domestica L.), but produce permanent effects in large milkweed bugs ( Oncopeltus fasciatus Dallas). Flies are able to eliminate large amounts of both compounds through excretion and metabolism, whereas neither method of elimination was found in milkweed bugs.