Search

Crosses were made between the Asian cockroach, Blattella asahinai Mizukubo, and resistant strains of the German cockroach, B. germanica (L.), to assess the transfer of pyrethroid resistance to the progeny and to study the inheritance mechanism(s) involved. It was shown that the strain of Asian cockroaches studied was susceptible to four pyrethroids. F 1 progeny were essentially susceptible to the same compounds. Tests with F 2 progeny and those from backcrosses to the resistant parent indicated that the data for each pyrethroid fit an hypothesis of simple, autosomal, nearly completely recessive inheritance. The results are discussed from the standpoint of the impact of the Asian genome on the inheritance mechanism(s)

Twelve field-collected populations of German cockroaches, Blattella germanica (L.), were examined for resistance to dietary abamectin at 40 ppm. Half of these populations had significantly increased resistance ratios compared with the VPI-susceptible strain, but the highest value was only 2.4. Feeding inhibition was variable but nevertheless pronounced in all 12 strains. Feeding-choice tests with two strains revealed that each strain consumed treated and untreated food about equally. Mortality was reduced in both strains. Cross-resistance from cyclodiene resistance was not found. Low-level selections with abamectin did not result in increased resistance. Whereas resistance to abamectin does not appear to be a problem at present, two potential resistance mechanisms were identified and are discussed briefly.

The response of a susceptible and two pyrethroid-resistant field strains of the German cockroach, Blattella germanica, to four emulsifiable concentrates (ECs)--Tempo (cyfluthrin), Demon (cypermethrin), Dursban (chlorpyrifos) LO, and XRM 5184 (chlorpyrifos)--was investigated. Application rates were 0.4, 0.1, 0.5, and 0.5%, respectively. Susceptible cockroaches avoided dried formulations of the pyrethroids Tempo and Demon, but resistant cockroaches did not; avoidance was greater with Demon than with Tempo. Filter papers freshly impregnated (wet) with Demon and Tempo flushed susceptible cockroaches (Demon greater than Tempo). Resistant cockroaches were flushed only by Demon, but less so than susceptible strain cockroaches. No mortality occurred in experiments with the pyrethroids. Dried formulations of Dursban LO and XRM 5184 had little, if any, repellency to nymphs of either the susceptible or resistant strains. Initially (1-3 h), most cockroaches settled on treated papers. Subsequent movement off treated papers was a step in the process leading to knockdown. At 24 h, mortality of susceptible cockroaches was 100% in the experiment with Dursban LO and 95% in the experiment with XRM 5184. Highest mortality in a resistant strain (40%) was in the contact experiment with Dursban LO. In contact repellency and flushing experiments, mortality was higher with Dursban LO than with XRM 5184. Neither chlorpyrifos formulation flushed cockroaches effectively. Mortality in flushing experiments was less than in the contact repellency experiments.

Selection experiments with a pyrethrins-susceptible and a pyrethrins-resistant strain of German cockroaches, Blattella germanica (L.), were conducted for 17 generations with either permethrin or fenvalerate as the selecting agent. Large nymphs were left on treated glass surfaces for extended periods of time each generation. Mortality was assessed at 24 h. The level of resistance was determined periodically by time-mortality testing. The VPI-susceptible strain served as the basis for comparison. The pyrethrins-susceptible strain developed resistance to pyrethrins early in the selection process; this strain ultimately became resistant to allethrin, phenothrin, permethrin, fenvalerate, cyfluthrin, and cypermethrin. Fenvalerate caused faster development of resistance than did permethrin. The pyrethrins-resistant strain, selected with fenvalerate, quickly became resistant to allethrin, permethrin, phenothrin, and fenvalerate. Ultimately, it developed resistance to all nine pyrethroids tested.

The toxicity of synergism of and resistance to insecticides in four strains of German cockroach, Blattella germanica (L.), were investigated. Toxicity of nine insecticides by topical application to the susceptible strain varied greater than 2,000-fold, with deltamethrin (LD50 = 0.004 micrograms per cockroach) and malathion (LD50 = 8.4 micrograms per cockroach) being the most and least toxic, respectively. Resistance to pyrethrins (9.5-fold) in the Kenly strain was unaffected by the synergists piperonyl butoxide (PBO) or S,S,S-tributylphosphorotrithioate (DEF), suggesting that the metabolism is not involved in this case. Malathion resistance in the Rutgers strain was suppressible with PBO, implicating oxidative metabolism as a resistance mechanism. The Ectiban-R strain was resistant to all the pyrethroids tested, and cypermethrin resistance was not suppressible with PBO or DEF. These findings support results of previous studies that indicated this train has a kdr-like mechanism. Bendiocarb resistance in both the Kenly and Rutgers strains was partially suppressed by either PBO or DEF, suggesting that oxidative and hydrolytic metabolism are involved in the resistance. Trends between the effects of the synergists on the susceptible versus resistant strains are discussed.

1. 1. Female Parcoblalta fulvescens feed selectively on diets differing in nutrient content when given a choice during the reproductive cycle. 2. 2. Diets high in carbohydrate and protein content are preferred early in the cycle, while a cellulose-containing diet is readily consumed toward the end of the cycle. 3. 3. The total diet consumed by females given a choice contained about 16% protein, and they did not excrete uric acid while on this diet. 4. 4. Females on diets high in carbohydrate or cellulose required longer to complete the reproductive cycle than females on high-protein diet or those given a dietary choice. 5. 5. Nitrogen-stressed females will consume urate-containing fecal pellets, but only if they have utilizable carbohydrate in their diet.

Pyrethrins resistance was assessed genetically in the German cockroach, Blattella germanica (L.), by conventional crossing experiments. It is inherited as a simple, autosomal, incompletely dominant, trait. By manipulating the test procedure, the susceptible homozygote was clearly identified, allowing gene frequency estimates to be made using the Hardy-Weinburg equilibrium expression. Gene frequencies were estimated for four susceptible and 16 resistant field-collected populations. Values ranged from 0.10 to 0.18 for the susceptible strains, and from 0.34 to > 0.90 for the resistant strains. Changes in gene frequency over time for several resistant strains were not significant. The results are discussed from the standpoints of their effects on cockroach control and the stability of pyrethrins resistance even during extended periods with no selection pressure.

The level of resistance to seven pyrethroids was followed in a laboratory-selected population of Blattella germanica (L.) for 15 generations, during which time it was not exposed to any insecticide. As estimated by LT50 resistance ratios (RRs), resistance declined in a stepwise manner to preselection levels with all of the pyrethroids except pyrethrins. I also compared the levels of resistance as indicated by RRs and by gene frequency (GF) estimates. Results showed that GF estimates provide a more precise indication of the changes in resistance that occur over time than do RRs alone, especially when combined with RR and end-point mortality data. I discuss my results from the standpoints of the number of genetic mechanisms involved in pyrethroid resistance in this insect, and what the declines in resistance mean for future cockroach control.

Ten field-collected strains of the German cockroach, Blattella germanica (L.), with varying levels of pyrethroid resistance were tested for possible cross-resistance to abamectin administered as a bait. The time-mortality method was used for comparison of response with a known susceptible strain in 10-d feeding experiments. Essentially no resistance to abamectin was found. Extensive feeding inhibition occurred after a few days, but the amount of abamectin consumed varied substantially from strain to strain. Abamectin may have considerable potential as a cockroach bait insecticide.

Several patterns of uric acid voiding exist among various cockroach species. The impact of dietary nitrogen levels on these patterns has now been examined. Blattella germanica, Supella longipalpa, and Latiblattella inornata do not void uric acid even when maintained on diets containing 10.6% nitrogen for up to 30 days. Two species of Nahublattella void some uric acid on that diet, but high mortality was observed by 15 days. Parcoblatta fulvescens voids increasing amounts of uric acid as formed pellets when dietary nitrogen is increased, and suffers no untoward effects. The partitioning of injected 14C-purine (hypoxanthine) by Parcoblatta was shown to occur first by conversion to 14C-uric acid. Thereafter, 14C is found in evolved 14CO2, feces, egg cases, and whole body. The partitioning of 14C is influenced by the level of dietary nitrogen available. On a nitrogen-restricted diet, larger amounts of 14CO2 are evolved but little 14C occurs in the feces. When nitrogen is abundant, reduced amounts of 14CO2 are evolved and more 14C is voided with the feces. 14C-containing compounds, including 14C-uric acid, are incorporated into egg cases. Radiolabel remaining in the injected insects at the end of the experiment was also influenced by the dietary regime. These results are discussed in relation to the flow of uric acid through Parcoblatta and its utilization by this insect.

1. 1. Crude extracts of concentrations of endosymbionts from newly formed cockroach oothecae have been assayed anaerobically and aerobically for enzyme activity related to the degradation of uric acid. 2. 2. The extracts exhibited uric acid-dependent oxidation of both methyl viologen and NADH 2 when strictly anaerobic conditions were maintained throughout the extraction and assay procedures. 3. 3. Under aerobic conditions, extracts from egg endosymbionts and cockroach fat body catalyzed the xanthine-dependent reduction of NAD + . 4. 4. The enzyme activity exhibited is strikingly similar to that of xanthine dehydrogenase. 5. 5. The significance of these results is discussed in relation to uric acid storage in the cockroach fat body.

Food and water consumption by adult female German cockroaches has been examined in relation to the reproductive cycle. Daily consumption was recorded for individual insects and was related to certain landmark events in each of four egg-case production cycles. It was shown that peaks of feeding and drinking occur during the egg maturation period, but are abruptly terminated at the appearance of each egg case. During the period when females carry the egg case, they feed and drink sparingly. The possible role played by feeding and especially drinking in the regulation of reproduction in this important pest species is discussed. RESUME Consommation d'eau et d'aliments pendant le cycle reproductif des femelles de Blattella germanica L'examen de la consommation d'eau et d'aliments par les femelles adultes de Blattella germanica a ete lie au cycle reproductif. La consommation individuelle quotidienne des insectes a ete reliee a certains evenements marquants dans chacun de quatre cycles de production d'ootheque. Les pics d'alimentation et d'absorption se produisaient pendant la periode de maturation des oeufs, mais disparaissaient brutalement a l'apparition de chaque ootheque. Pendant la periode ou les femelles portent les ootheques, elles s'alimentent et s'abreuvent parcimonieusement. Le role eventuel joue par l'alimentation et particulierement l'absorption dans la regulation de la reproduction de cet important insecte nuisible est examine.

1. 1. Young adult American cockroaches ( Periplaneta americana L.) were allowed to accumulate nitrogen stores by maintenance on a highly positive nitrogen balance diet. Upon removal to one of three negative nitrogen balance diets, dietary nitrogen intake, body nitrogen uptake, body uric acid content and nitrogen elimination were monitored. 2. 2. Changes in body nitrogen, uric acid nitrogen and body weight were observed when cockroaches were placed on negative nitrogen balance regimes. The rate of uric acid mobilization was related to the amount of carbohydrate and nitrogen present in the diet. Insects maintained on dextrin for 17 weeks mobilized urate stores most rapidly. 3. 3. Females mobilized urate stores more rapidly than males. Oothecal production accounted for a considerable portion of the nitrogen lost. Comparisons of the nitrogen balance values suggest that a portion of the uric acid nitrogen is utilized during egg production and may be incorporated into the ootheca. 4. 4. The mobilization of urate stores may involve the mycetocyte symbionts as well as the metabolic processes of the insect. Mobilization and utilization of nitrogen contained in stored urates is briefly discussed.

1. 1. Uric acid has been positively identified in the Malpighian tubules of three urate-voiding cockroach species—Parcoblatta fulvescens (S. and Z.), Shawella couloniana (S.) and Simploce hospes (P.). 2. 2. In secreting tubules, uric acid occurs in the lumen of the middle and proximal regions and occasionally in the distal tips. 3. 3. Urates are present in the tubule lumen as small spherules which form an opaque white slurry. 4. 4. Urates are discharged into the hindgut in sufficient quantities to obscure the presence of food residues in urate-containing fecal pellets. 5. 5. Birefringent materials occur in vacuoles within the tubule cells, which may indicate vesicular transport of urate.

1. 1. Five additional cockroach species were shown to void uric acid to the exterior bringing the total to nine out of 49 species examined. All nine belong to the subfamily Blattellinae. 2. 2. Uric acid content in whole excreta from six species of Parcoblatta varied from 5.7 to 11.2%, while that in the white, formed-pellets varied from 25.4 to 36.1%. 3. 3. Young Parcoblattait nymphs void little uric acid during the first month of life, but subsequently expel it at adult rates. 4. 4. Fat body from 35 species of cockroaches has a consistent general cytological pattern involving three cell types. 5. 5. Fat body from all species examined contains uric acid within urate cells. 6. 6. Several possible strategies for urate utilization by cockroaches are discussed.

Newly emerged adult female Parcoblatta fulvescens (Saussure & Zehntner) mate ca. 10 days after emergence and produce their first ootheca 5 days later. All matings occurred between 0230 and 0700 hours and lasted an average of 100 ± 40 (±SEM) min. Subsequently, females of this species and P. pennsylvanica (DeGeer) produce an ootheca about every 8 days. They feed extensively during the period from oothecal deposition to appearance of the next ootheca. This is necessary to support sustained reproduction because each ootheca equals 15–20% of female body weight. Oothecae of five Parcoblatta species have been compared in size and number of egg compartments. P. pennsylvanica from Texas has been shown to undergo two complete generations per year in the laboratory.

o 1. Nitrogen and cation excretion/storage in 23 cockroach species representing 11 subfamilies have been examined. Measurements of externally excreted ammonia nitrogen, uric acid nitrogen, total nitrogen, potassium and sodium were made. Values of total body nitrogen, body urate nitrogen, and body potassium and sodium are also reported. 2. A significant correlation was found between body nitrogen and body uric acid nitrogen. Certain species contained very high levels of uric acid/urates representing as much as 72% of their total body nitrogen. Contrarily, other species were found to contain low levels of uric acid/urates, representing as little as 3% of their body nitrogen. 3. A less significant correlation was found between internal nitrogen storage and external nitrogen excretion. Certain species can be classified as uricotelic, since as much as 62% of their total fecal nitrogen may be excreted as uric acid-nitrogen. Other species can be designated as ammonotelic, since they may excrete as much as 70% of their total fecal nitrogen as ammonia nitrogen. 4. Increased body nitrogen retention may be correlated with increases in body potassium and/or sodium. The internal storage of nitrogen as uric acid appears to involve the formation of potassium and/or sodium urate salts.

1. 1. Adult female Parcobtatta pennsylvanica and P. fulvescens exhibit pronounced feeding and drinking cycles during their 8-day reproductive cycle. 2. 2. Food and/or water deprivation at oothecal deposition markedly inhibited basal oocyte development. 3. 3. The voiding of urate-containing fecal pellets by P. fulvescens is also cyclic, and peaked 1 day after peak feeding. It occurred only in females on high-nitrogen diets. 4. 4. Females on a graded series of nitrogen diets did not show a progressive increase in the level of body urate on the higher nitrogen diets, suggesting that urate excretion plays a role in regulating the level of internal urates.

Newly emerged adult female German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae) fed avermectin B1 at concentrations of 6.5 ppm and higher in the food exhibited high mortality at 10 days. Survivors of these dosages failed to reproduce. Lower dosages produced some mortality and inhibited mating and reproduction. Those individuals that did reproduce had normal-sized oothecae and the percent hatch was normal. The higher concentrations produced a marked inhibition of feeding which appeared to be related to toxicity rather than to unpalatability or repellency. When nymphs were fed avermectin B1 for short periods, higher dosages were required to produce mortality. Young nymphs were the most susceptible. Feeding inhibition also occurred in these short-term studies, but the survivors reproduced normally as did the progeny from the females fed avermectin continuously. The possible use of avermectin B1 in baits for cockroach control is discussed. RESUME Effets de la consommation d'avermectine B1 sur la mortalite et la reproduction de Blattella germanica (Dictyoptera: Blattellidae) Alimentees peu apres la mue imaginale avec une nourriture contenant 6,5 ppm ou plus d'avermectine B1, des femelles de B. germanica L. ont presente une forte mortalite a 10 jours; les survivantes ne se sont pas reproduites. Des doses plus faibles ont provoque quelque mortalite et quelque inhibition des accouplements et de la reproduction; les individus qui se sont reproduits avaient des ootheques de taille normale et le taux d'eclosion etait correct. Les concentrations plus elevees ont provoque une nette inhibition de l'alimentation, qui semblait etre plus due a la toxicite qu'a la repulsion ou au gout. Quand des larves âgees ont ete alimentees avec de l'avermectine B1 pendant de breves periodes, des doses plus elevees etaient necessaires pour provoquer la mortalite. Les jeunes larves etaient les plus sensibles. Une inhibition de l'alimentation apparut dans ces etudes a court terme, mais les survivants se reproduisirent normalement, comme le firent les descendants des femelles alimentees continuellement avec de l'avermectine. La discussion porte sur l'utilisation eventuelle de l'avermectine B1 dans des appâts pour lutter contre les blattes.

1. 1. Thirty one additional cockroach species have been examined with respect to external voiding of uric acid. Eight of them, belonging to the subfamily Plectopterinae, void formed-urate pellets sparingly. 2. 2. Two species of Ischnoptera void urates admixed with feces at the rate of 2% by weight. 3. 3. The leaf mantid voids urates admixed with feces at the rate of about 20% by weight. 4. 4. The ability of adult female Parcoblatta fulvescens to avoid urate pellets can be altered by varying dietary nitrogen levels. 5. 5. The importance of these results to understanding the various nitrogen strategies found among cockroaches is discussed.

NAD-and NADP-linked isocitrate dehydrogenases (ICDH) have been identified in fly and cockroach thoracic muscle mitochondria. The NAD-linked enzymes from both species have been partially purified from mitochondrial acetone powders. The fly enzyme has been studied in detail. This enzyme is very stable and can be stored in 30 per cent saturated ammonium sulphate containing 20 mM phosphate buffer at pH 7.0 for 3 weeks at room temperature without loss of activity. Mg++ and Mn++ stimulate activity optimally at concentrations equivalent to substrate concentration. ADP stimulates activity optimally at 2 mM in conjunction with NAD+ (4mM), isocitrate (6 mM), and Mg++ (6 mM). Other properties of the enzyme are also described, and a discussion is included.

The toxic effects of 8 carbamate insecticides have been compared in susceptible and carbaryl-resistant strains of Blattella germanica (L.). Baygon® ( o -isopropoxyphenyl methylcarbamate) and UC-10854 ( m -isopropylphenyl methylcarbamate) effectively killed cockroaches of both strains with a topical method of application. Dimetilan and Isolan® (l-isopropyl-3-methyl-5-pyrazolyl dimethyl-carbamate) were less toxic, and there was little resistance to these materials in the carbaryl-resistant cockroaches. Susceptible cockroaches were killed effectively by UC-21149 (2-methyl-2-(methylthio)propionaldehyde O -(methylcarbamoyl)oxime) and Matacil® (4-(dimethylamino)-m-lolyl methylcarbamate), but there was evidence of cross resistance to these compounds in the resistant strain. Cross resistance to MC-A-600 (benzo[b]thien-4-yl methyl carbamate) occurred in carbaryl-resistant cockroaches when a topical method of application was used. There was no apparent cross resistance to this material when a dipping technique was employed for testing. Carbaryl was ineffective in killing cockroaches of either strain by the topical method; as expected, significant levels of resistance were demonstrated in the resistant strain with a dipping technique.

Mitochondria isolated from cockroach thoracic muscles have been used to demonstrate that the rate of oxidation of several Krebs-cycle intermediates is under the control of adenosine diphosphate concentration. Respiratory-control indices as high as 25 have been achieved with both pyruvate and glutamate. Contrarily, the rate of oxidation of α-glycerol phosphate is influenced by adenosine diphosphate concentration to only a minor degree, but is markedly inhibited by accumulation of the oxidation product. When the ratio [reactant]/[product] is approx. 3, oxidation of α-glycerol phosphate becomes very low. These findings are used to propose a theory which may satisfactorily explain the problem of respiratory control in insect muscles.

A preliminary survey of mitotic and meiotic cells from 12 cockroach species was made. Cells were obtained from embryonic and testicular tissues and were prepared by the squash technique. Haploid and diploid numbers were either established or confirmed for each species. Diploid numbers ranged from 20 in Supella to 74 in Blaberus , with numbers of 24 and 28 being common to several species. Chromosome size appeared to vary inversely with chromosome number. The XO sex determination mechanism was confirmed, and the X chromosome was identified in at least 2 species. Observations on centromere location and on certain unusual chromosome situations are also presented.

1. 1. Four protein fractions with ATPase activity have been obtained from cockroach thoracic muscle mitochondria. 2. 2. Purifications of forty- to one hundredfold were achieved using ultracentrifugarion, (NH 4 ) 2 SO 4 fractionation and column chromatography on Sephadex and on DEAE cellulose. 3. 3. ATPase IV appears to be specific for purine nucleoside triphosphates, while the other three dephosphorylate purine and pyrimidine nucleoside di- and triphosphates. ATPase I degrades nucleoside monophosphates. Evidence on the cold lability of the four enzymed is also presented. 4. 4. These results are discussed in relation to the ability of insect sarcosomes to degrade ATP.

Three glutamic acid-metabolizing enzymes have been identified and partially purified from cockroach thoracic muscle mitochondria. The enzymes are glutamic dehydrogenase, glutamic-aspartic transaminase and glutamic-alanine transaminase. The glutamic dehydrogenase appears to be NAD+ specific, while the two transaminases require pyridoxal phosphate. Substrate specificity, pH optima, and several other characteristics of each enzyme have been determined.

1. 1. The excreta from twenty species of cockroaches have been examined for the presence of uric acid by several methods of analysis. 2. 2. Uric acid is voided by only three of these species (Shawella couloniana, Symploce hospes and Parcoblatta spp.) all belonging to the subfamily Blattellinae. 3. 3. Each of these species voids uric acid in formed pellets which are separate from the fecal wastes, and which contain a high percentage of uric acid. 4. 4. Blattella germanica, which belongs to the same subfamily, eliminates small amounts of uric acid, but the mechanism appears to be entirely different. 5. 5. The fat body of fourteen species was shown to contain uric acid stores. 6. 6. The significance of these results is discussed in terms of phytogeny, species biology, pellet formation and functioning of the malpighian tubules.

The effects of nitrogen balance on uric acid/urate, K+ and Na+ storage or mobilization were examined in the American cockroach Periplaneta americana (L.). Cockroaches on a high nitrogen diet increased in whole body uric acid/urates, K+ and Na+. Those on a semi-starvation diet maintained fairly constant levels of uric acid/urates, K+ and Na+. However, those on a low nitrogen diet mobilized stored uric acid/urates and K+, but not Na+. Analyses for uric/urates K+, Na+, Ca2+ and Mg2+ in fat body tissue from insects maintained on 12 diets containing different concentrations and sources of dietary nitrogen showed that only K+ concentration could be correlated with fat body uric acid/urate storage. Whole body storage and mobilization of uric acid/urates, K+ and Na+ were reflected in the faecal/dietary ratios of K+ and Na+. A model for a uric acid/urate ion sink which might be associated with ionic and osmotic balances is proposed, and some evidence for its existence is discussed.

1. Excreta from ten additional species of cockroaches have been analyzed for the presence of uric acid. 2. Uric acid is voided only by Parcoblatta pennsylvanica which belongs to the subfamily Blattellinae. 3. The urate voiding mechanism appears to be the same as for three other species of this subfamily previously studied. 4. Internal urate deposits were demonstrated in eight species. 5. The house cricket voids a uniform, uric acid-containing excreta, but retains only small amounts of uric acid internally.

A pyrethrins-susceptible and a pyrethrins-resistant strain of German cockroaches, Blattella germanica (L.), were selected with either permethrin or fenvalerate over several generations to determine if resistance would occur. Large nymphs were left on treated glass surfaces until about half were killed each generation. The level of resistance was determined periodically by time-mortality testing. The VPI-susceptible strain served as the basis for comparison. The pyrethrins-susceptible strain developed resistance to pyrethrins in six to seven generations with either selecting agent. This strain also showed resistance to allethrin when fenvalerate was the selecting agent. The pyrethrins-resistant strain developed resistance to allethrin with both selecting agents; in addition, resistance to permethrin, phenothrin, and fenvalerate developed when fenvalerate was used. The synergists piperonyl butoxide and MGK 264 (2-(2-ethylhexyl)-3a,4,7,7a-tetrahydro-4,7-methano-1H-isoindolel, e(2H)-dione) largely negated resistance to pyrethrins, but neither they nor the esterase inhibitor DEF (S, S, S tributyl phosphorotrithioate) were effective after development of resistance to allethrin. While resistance to pyrethroids can easily develop in this species, both the selecting agent and the previous history of resistance appear to have a bearing on how resistance develops.

Several field-collected strains of German cockroaches, Blattella germanica (L.), were tested for resistance to bendiocarb or pyrethrins or both in the presence or absence of synergists. Large nymphs were exposed to toxicants on glass surfaces. All strains tested had high-level resistance to bendiocarb: a few were highly resistant to pyrethrins. The synergists piperonyl butoxide and MGK 264, 2-(2-ethylhexyl)-3a,4,7,7a-tetrahydro-4,7-methano-1H-isoindole-1,3(2H)-dione, both successfully negated resistance to bendiocarb and pyrethrins. Combinations of these insecticides with either synergist also effectively eliminated resistance. A commercial product (Ficam Plus) containing bendiocarb, pyrethrins, and piperonyl butoxide rendered eight bendiocarb-resistant strains susceptible. These results indicate that the resistance mechanism to both bendiocarb and pyrethrins probably may be attributed to an enhanced microsomal mixed-function oxidase system which is effectively inhibited by either synergist.

The synthesis and properties of a new double translocation heterozygote in B germanica, combining T (8;9) with the progressive interchange T (4;5;10), are described. Competitiveness and sterility data indicate that males are promising candidates for a "field" experiment in genetic control of a cockroach. Sterility from genetic load and embryonic trapping is complete. Disjunction properties of the parental interchanges are similar to those found in cells of the double males, but chiasma frequency of the interchanged chromosomes is increased. Evidence of a possible relationship between chiasma formation and disjunction type is discussed.

1. 1. Three fluorescing materials have been discovered in excreta from the American cockroach, Periplaneta americana (L.), and found to increase in concentration as dietary nitrogen increases. 2. 2. These compounds have been identified as kynurenic, xanthurenic and 8-hydroxyquinaldic acids. 3. 3. Feeding cockroaches antibiotic eliminates 8-hydoxyquinaldic acid production, presumably by inhibiting gut microbial dehydoxylation of xanthurenic acid. 4. 4. Excreta from wild-type and lavander-eye mutants contains all three metabolites, while that from pearl-eye mutants contains none of them. 5. 5. Xanthurenic and 8-hydroxyquinaldic acids may contribute to cockroach gut tumor formation.

During the investigation of a wing mutation in the German cockroach (Cochran & Ross 1961), sib-matings of some of these mutant roaches were made for several generations. From certain of these crosses there appeared roaches in which the body was twisted in a most unusual but consistent manner. Thus far attempts to mate twisted males and females have been unsuccessful. Twisted cockroaches have been successfully crossed with normal cockroaches, however, and normal-appearing offspring were produced. Most of these roaches were accidentally lost prior to maturation, but the trait has continued to appear in the inbred line which first produced it. More recently a few specimens have been found in other inbred lines as well. To date 15 twisted roaches have appeared in the original inbred line (3 in the F1, 3 in the F2, and 9 in the F3). A genetical basis for the trait is thus indicated, but as yet the mechanism is not clear. Therefore, the present note is primarily a morphological description of the abnormality.

In the course of certain investigations dealing with the German cockroach, Blattella germanica (L.), it became necessary to separate males and females prior to the final molt. To our knowledge, no method of sex determination in nymphs has previously been reported for this species. It is usually quite easy to distinguish the sexes in the last one or two nymphal instars by gross appearance, however, and this means has probably been used in the past. In the present paper a method is described by which it is possible to sex the nymphs in all instars including the first. The distinguishing characters are the presence or absence of a notch in the ninth sternum in the early instars and, in later instars, the presence or absence of the eighth and ninth sterna. Over 800 nymphs have been sexed by this method without error.

Although gynandromorphs are well known in several diverse insect groups, none have heretofore been described from a cockroach. Recently we found a single adult gynander in a laboratory-bred, DDT-resistant strain of the German cockroach, Blatella germanica (L.). Since little can be deduced from a single specimen in regard to genetic mechanisms, this note is limited to a brief mention of the more prominent morphological features.

FOR many years various cockroach species have been used extensively as experimental animals, particularly in physiological investigations and, more recently, in studies on insecticide resistance. Generally speaking, however, there is little known concerning the genetics of cockroaches. For some time we have carried out a search for heritable traits in the German cockroach, Blattella germanica (L.), along a somewhat similar line to that conducted in the mosquito, Aedes aegyptii, by Craig and VandeHey1,2, An autosomal recessive, balloon-wing3, and a tergal abnormality4 have already been described. The genetics of an orange-body colour mutation (or) is presented here, as well as the results of tests for linkage of this trait with balloon-wing (ba). Crosses with a DDT-resistant strain were also made, but the results are presented elsewhere5.