A quantitative and qualitative study of the behavioral effects of an insecticide on various life stages of the German cockroach, Blattella germanica (L.), was conducted. Comparisons between a susceptible laboratory strain (VPI) and a resistant field strain (BP) were made to examine the relationship between physiological resistance and behavioral resistance. The effects of vapors from a formulation of 1% propoxur in oil were compared with vapors from a mineral oil control. Vapors from the control had little effect on cockroach behavior. Adult males, adult females, and middle instars were repelled from aquaria containing the insecticide vapors. Early instars sought shelter in the pores of water sponges. No differences in behavior due to reproductive state were observed as females with oothecae and females without oothecae were equally repelled. Responses by adult males included increased movement, antennal grooming, and tarsal grooming. Electroantennogram studies showed that the vapors of the propoxur formulation were detected by the antennae. Adults of the susceptible VPI strain responded more strongly to the insecticide vapors, relative to the controls, than did adults of the resistant BP strain. The negative correlation between physiological resistance and behavioral responses was not due to the development of behavioral resistance. Rather the resistance mechanism of the BP strain was probably responsible for inhibiting the behavioral response of that strain. Responses to the propoxur insecticide may have been compounded by solvents in the formulation, but differences between the two strains were probably due to the propoxur. The oil base had no effect on cockroach behavior. That wet sponges provided safe harborage for the early instars indicates the importance of even short range dispersal. Also, the use of repellent barriers to exclude cockroaches from sensitive areas may become less effective if physiological resistance in cockroach populations is accompanied by decreased avoidance responses. Knowledge of the levels of physiological resistance must be supplemented by an understanding of the behavioral characteristics of insect populations for the successful development of pest control programs. / Ph. D.

The inheritance of resistance to chlordane in the German cockroach, Blattell germanica. (L.), was studied by determining the toxicity of chlordane to the following strains of roaches: a) chlordane-resistant and non-resistant strains, b)F₁ and F₂ progeny of reciprocal crosses between two parental strains, c) progeny of pair matings within resistant and non-resistant strains, and from a cross between resistant females and non-resistant males. / Ph. D.

Successive releases of male German cockroaches heterozygous for the translocation T(8;9) and the recessive deleterious gene sty were made into laboratory populations of Blattella germanica to study the effect of this genetic load on population growth. Five experimental populations and one control were followed by monthly census for eight months. Individual progeny groups were held in separate containers. Various aspects of reproductive behavior of different genotypes were evaluated in separate experiments including fecundity, competitiveness and assortative mating. Linkage between T(8;9) and sty was also measured. The translocation T(8;9) and sty were successfully introduced into the experimental populations by the introduction of heterozygous males. Experimental populations were only 50% the size of the control at the F₁ generation and only 25% as large by the F₂ generation. At the F₃ generation, experimental populations were only 15.4% as large as the control. Cross connected contingency table analyses of population data showed a significant retardation of population growth from releases of T(8;9) sty males. T(8;9) provided a successful mechanism for driving the deleterious gene, sty, into the normal segment of the population. The frequency of sty/sty females in F₂ groups was predicted at 0.20. Observed frequencies approached the expected frequency at 0.11 to 0.22. This deleterious gene provided additional genetic load by reducing possible F₃ progeny by approximately 15%. Linkage tests of T(8;9) with sty showed cross-over frequencies of less than 1% for both males and females. Results were less than optimum due to the following: a possible reduction in competitiveness of released males; higher than expected fecundity in the sty· homozygote female; possible shift in the frequency of alternate disjunction in T(8;9) sty heterozygote males; possible assortative mating between non-translocation bearing wildtype males and T+/+sty females in the population as well as T+/+sty males and non-translocation bearing wild-type females; fewer T+/+sty males and more sty males released than planned due to phenotyping errors in larger releases. Laboratory studies of the reproductive behavior of three genotypes involved in the experimental populations evaluated competitiveness among males, initial productivity, maximum number of matings per male, and assessed the prospect of assortative mating among the genotypes. Competitiveness of the T+/+sty males in small number tests was consistently better than wild-type males but in later assessments by mass mating and population studies, they demonstrated equal competitiveness with wild-type males. A statistically significant tendency toward assortative mating between VPI wild-type males and T+/+sty females was observed. The feasibility of techniques for mass rearing of semi-sterile males for releases of up to 10,000 males per month was demonstrated. / Ph. D.

Two age factors were studied: the age of the roach at the time of testing, and the age of the female parent at the time reproduction occurred. Age groups from 1-3 days to 25-28 days were used to test the first factor and the first three egg eases were used to test the latter. Age was found to be a statistically significant factor when malathion, aldrin, and DDT were tested on both sexes of the normal strain. However, because of inconsistencies and a lack of differences of any great magnitude, it is believed that the differences in all but the aldrin tests were of no biological significance. In the aldrin tests it appeared that as the age of the roach increased, susceptibIlity gradually increased. The tests using aldrin on the Aldrin-resistant strain were significant for the females. Resistance in this strain appeared to increase from the 1-3 day age group until it reached a peak in the 10-12 day age group, then decreased to a level equal to or lower than that of the younger age groups. Statistical significance was found for the parental age factor in about one-half of the tests. However, it was of little biological significance because the variations were of a small magnitude and inconsistencies between the males and females occurred of ten. / Master of Science

German cockroach, Blattella germanica L., females of resistant and non-resistant strains carrying oothecae were exposed to filter paper impregnated with propoxur, malathion, and diazinon. Premature oothecal drop was monitored during the exposure period and for 24 hours thereafter. Determinations of female mortality were also made 72 h post-exposure. Oothecae from exposed females were observed for percentage egg hatch, time from exposure to hatch, percentage nymphal emergence, nymphal survival, and the percentage of nymphs able to move about freely 24 hours post-emergence. The comparisons of these factors were made not only on prematurely dropped oothecae but also on oothecae retained by females, and oothecae that were manually detached from females. Premature oothecae dropped and those manually detached were hatched on an insecticide treated surface. Premature oothecal drop occurred in all experiments, but was delayed 24 h in experiments with organophosphates. The mortality of treated females which prematurely dropped their oothecae was higher than females retaining them (73% vs. 53%). Percentage nymphal emergence and survival were reduced when oothecae were placed on an insecticide treated surface. The significantly higher survival of resistant strain nymphs (Carver, 60%, and Lynn Haven, 99%) in a comparison to nymphs of a susceptible strain (VPI, 45%) on insecticide treated surfaces provides evidence for resistance in first instar nymphs. A procedure for the quantitative comparison of the effects of different insecticides on oothecal-bearing females has been developed. Insecticides which cause a higher percentage of premature oothecal drop may reduce regrowth of a cockroach population when compared to materials which do not, even if the insecticides cause similar mortality. The extent to which population regrowth occurs depends on whether oothecae hatch on a treated surface, oothecal age, and environmental conditions. / Master of Science

This research concerns the effects that harborage limitation and habitat isolation have on German cockroach control in urban housing apartments. Standard Mason jar traps were used to survey cockroach populations, trap cockroaches for marking and population census, and detect cockroaches that moved from the original capture sites. Focus apartments (ie. apartments with large cockroach populations) were located and used for the two studies. Five focus apartments were used for the harborage limitation study. All harborage and harborage access in the kitchen and bathroom areas were sealed in three treatment apartments. These areas were not sealed in the two control apartments. Eight focus apartments were used for the habitat isolation study. Three treatment apartments had all accessways (holes and cracks) between the focus and the adjacent apartments sealed. Five control apartments were not sealed. Cockroaches in the three treatment apartments were captured, marked and released at the point of capture. Harborage limitation focus apartments were sprayed with 0. 5% chlorpyrifos in water and habitat isolation focus apartments were sprayed with a 0.25% synergized pyrethrin aerosol. Percentage control for the harborage limitation study was determined and no significant differences (P<0.1%) between treatment and control apartments were found. Percentage movement for the habitat isolation study was determined and no significant differences (P<0. 1%) between treatments and controls were noted. Neither harborage limitation nor habitat isolation would be recommended as a cockroach control technique unless they are used in concert with other control techniques. / Master of Science

This investigation represents the first thorough examination of chiasma frequency in the primitive orthopteroid insect, <u>Blattella germanica </u> (L.). The data obtained are useful both in advancing our knowledge of cockroach genetics and in stimulating comparative cytogenetic studies. A pilot study was conducted to ascertain appropriate sample sizes and to assess the feasibility of more extensive investigations. Experimental animals were reared in a constant temperature and humidity chamber and segregated according to whether they emerged from a first, second, or third ootheca. The testes of third to fourth instar male nymphs were removed, stained with acetic orcein, and examined for suitable numbers of cells at diplotene-diakinesis. Analysis of the chiasma frequency data showed a decrease in mean chiasmata per bivalent: 1.3325 ± 0.0184 for the first oothecal group, 1.2999 ± 0.0165 for the second oothecal group, and 1.2525 ± 0.0113 for the third oothecal group. The variances decline with the means. The chiasma frequency of a stock heterozygous for a reciprocal translocation involving two mid-sized chromosomes, eight and nine, was compared to the wild-type freq9encies. In comparison with the first oothecal group, an elevated chiasma frequency, 1.4176 ± 0.0062 chiasma per bivalent, was found. The translocation had the effect of raising chiasma frequency in the two bivalents involved. No interchromosomal effect on chiasma frequency was observed, due to the presence of the translocation. It was noted that in B. germanica, chiasma frequency is probably not positively correlated with bivalent length. / Master of Science

Resistant and susceptible field strains of the German cockroach were compared for possible chromosome aberrations. Resistant strain females produced significantly higher numbers of aberrant oothecae ( >5 unhatched eggs ) than the susceptible strains. Chromosome aberrations found in the susceptible strains were attachments (autosome-autosome, autosome-x) and fragments that did not reappear in outcrosses. Attachments (autosome-autosome, autosome-x), fragments, three translocation configurations that did not reappear in outcrosses and two reciprocal translocation heterozygotes occurred in the resistant strains. These two translocations have been tentatively identified as T(12:8)/12:8 from the Bowl strain and T(11:6)/11:6 from the K851 strain. T(12:8)/12:8 exhibits random disjunction at metaphase I. There were no differences related to susceptible vs. resistant strains in the frequency of chromosome aberrations from the aberrant oothecae. There was no evidence, except in the K851 strain, to support a relationship between egg arrest and chromosome aberrations, or the hypothesis that chromosome aberrations result from the selective pressure of insecticides. It is suggested by this study that translocations are the most common type of “floating” polymorphism in the German cockroach. The first occurrence of three known phenotypic mutants, bent bristle, yellow body, and pallid eye, and one new phenotypic mutant, colorless eye, in field strains are reported by this study. / Master of Science

The studies presented here are an effort toward learning about the behavior of small mixed populations of German cockroaches. Of particular interest was the effect of female cockroaches on the behavior of the group, particularly the group formation within a harborage and the dispersal from a harborage. The effect of females was looked at with respect to female density and reproductive state. Populations aggregated at low female densities. This response increased when densities of gravid females increased but decreased when densities of non-gravid females increased. The effects of female reproductive state on dispersal could not be determined as non-gravid females developed egg cases by the end of the study. Increased female density caused increased dispersal of females and mid-instars. The mid-instars were the primary dispersers in each experiment. Early instars, excluding escapees, dispersed least. The results of these studies indicate the females of a population can mediate the behavior of that population and its members. It is postulated that this may be achieved by the production and/or regulation of sex, aggregation, and dispersal-inducing pheromones by females. / Master of Science

The overall purpose of this study was to examine the effects of an insecticide vapor pulse on the dispersal response of the German cockroach, Blattella germanica (L). An apparatus was designed to expose test cockroaches to vapors from commercial pesticide formulations. Insecticide vapor-induced dispersal responses were recorded during a two hour period from different strains that had been allowed to acclimate to a harborage. The dispersal response of large nymphs from a pesticide susceptible laboratory strain (VPI) was compared to two propoxur resistant field strains (Carver, Kenly) after exposure to four propoxur formulations and their blanks. Vapors from the petroleum-based oil and aerosol formulations induced significantly more dispersal than vapors from water-based emulsifiable concentrate and wettable powder formulations. Vapors from formulations containing the toxicant generally induced a significantly faster dispersal response than did their blanks. Exposure of cockroaches to the vapors of diazinon, malathion, and cyfluthrin indicated that the class of pesticide can also influence the dispersal response. Strain differences were found in experiments with the propoxur formulations, their blanks, malathion, and cyfluthrin. Slow dispersal precluded demonstration of significant strain differences in experiments with diazinon. Exposure of mixed age groups of four strains to vapors from 1% propoxur-in-oil, an aerosol and their blanks indicated that dispersal patterns were similar to the single age class experiments. Inter- and intra-strain differences were found. Dispersal of the field strains was distinguished from that of the laboratory strain by more variable responses and differences among age classes. The strongest inter-and intra-strain differences were in response to the solvents rather than the complete formulation. The air concentration of propoxur from a 1% oil formulation was estimated at 146 pg/ml. Condensation of the toxicant onto the apparatus was also observed. Vapor pulse characteristics for the four propoxur formulations indicated that the equilibrium vaporization rate in the test apparatus was approximately 0.5 mg/min for the oil and aerosol formulations and 1.0 mg/min for the WP and EC formulations. Results suggest that effective control strategies must be tailored for each target population. / Ph. D.