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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.

Metaphase I cells from heterozygotes in eight reciprocal chromosome translocation stocks of Blattella germanica (L.) have been examined and counted. The data show that three stocks have random disjunction (adjacent and alternate orientations are equally frequent), but the cell types adjacent-1, alternate-1, adjacent-2, and alternate-2 are present in a ratio of 2∶1∶1∶2. Four stocks with directed disjunction have similar patterns, except for a heavy preponderance of alternate-2 cells. This difference is reflected in the finding that 60–65% of all cells in these interchanges are type II cells (alternate-2 plus adjacent-2), and the individual percentages agree closely with the percent directed disjunction in each case. One inter-change with directed disjunction is distinctly different in that the frequencies of both alternate-1 and alternate-2 cells are elevated and contribute to directed disjunction. It has also been demonstrated with two stocks that changes in disjunction frequencies can be brought about by genetic manipulation. These observations provide a better understanding of the differences between random and directed disjunction.

The evidence in support of two types of alternate disjunction in translocation heterozygotes from the German cockroach, Blattella germanica(L.), is reviewed. When unique cytomorphological features occur in the translocation figure, the two types of alternate disjunction are identifiable regardless of the angle of observation. Photographs supporting this contention are presented for alternate-1 and alternate-2 disjunction in T(7;12)/7;12. Other evidence in support of the existence of alternate-2 disjunction is also presented.

Two eye-color mutations in the American cockroach, Periplaneta americana (L.), are reported. The names proposed for these mutants are “pearl” and “lavender.” Crosses with wild-type individuals established that both traits are inherited as single autosomal recessives. Crosses between pearl and lavender proved that the two traits are inherited independently, but that the double recessive is phenotypically pearl. Since both mutants are tryptophan accumulators, this result can be explained by assuming that the lesion producing pearl occurs first in the biosynthetic pathway. Experiments involving parabiotically joined lavender and wild-type nymphs have also been performed. There was no change in the eye color of either partner even after two molts. This confirms an earlier report involving parabiotically joined pearl and wild-type nymphs.

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.

Adjacent-1, alternate-1, adjacent-2, and alternate-2 disjunction configurations were observed cytologically at metaphase I in heterozygotes from two reciprocal chromosome translocations in the German cockroach, Blattella germanica (L.). T(7; 12) shows random disjunction and the frequencies of the above four types were in a ratio of 2:1:1:2 (p greater than 0.90). T(3; 12) has directed disjunction (about 70% alternate) which is attributable to a heavy preponderance of alternate-2. No interpretable ratio occurs here except for the equality of alternate-1 and adjacent-2 types. These observations confirm the existence of two types of alternate disjunction, and provide insight into the basis for random vs directed disjunction.

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.

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.