Calling behavior of the female german cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Virgin German cockroach females, Blattella germanica(L.), were observed, for the first time, to exhibit a characteristic calling behavior during which females emit a volatile sex pheromone. Under a photoperiod of 12L12D, the percentage of 7-day-old virgin females that exhibited this behavior peaked before the end of the scotophase in a similar pattern to the diel periodicity of mating. A clear relationship was evident between calling and stages of sexual receptivity during successive gonotrophic cycles. Females initiated calling 5–6 days after the imaginal molt, when their basal oocytes were 1.6 mm long. If not mated, females continued to exhibit bouts of calling during the next 3–4 days until 24 h before ovulation. Calling was completely suppressed by mating as well as the presence of an egg case in the genital atrium in both virgin and mated gravid females. We suggest that calling and the emission of a volatile sex pheromone serve to attract males from a distance as well as to potentiate responses to contact sex pheromone in aggregations.     

A microdialysis study of allatostatin degradation in Blattella germanica (L.) (Dictyoptera, Blattellidae)

Allatostatins with a typical C‐terminal sequence YXFGL‐NH₂ are insect neuropeptides with inhibitory properties upon Juvenile Hormone production in the corpora allata, vitellogenin release by the fat body, and gut and dorsal vessel motility. All these biological effects are rapidly reversible, suggesting the occurrence of effective mechanisms for inactivation of the peptides. We have studied the degradation of DRLYSFGL‐NH₂ (BLAST‐2), one of the allatostatins of Blattella germanica, in the internal milieu of adult females of this cockroach. The experimental approach combined the use of the radioiodinated derivative [¹²⁵I‐Tyr⁴]BLAST‐2, microdialysis techniques and HPLC analysis with a radioisotope detector. Under these experimental conditions, the half‐life of BLAST‐2 in the internal milieu of the adult female of B. germanica was between 3 and 6 min. Such a short half‐life explains the high doses of allatostatins required to obtain the expected biological effects when tested in vivo, and suggests that circulating allatostatins are subject to rapid rates of synthesis and degradation in order to be operative physiologically.     

Hydramethylnon uptake by Blattella germanica (Orthoptera: Blattellidae) by coprophagy

Blattella germanica (L.) that were fed hydramethylnon bait produced residues that were toxic to exposed conspecifics. Insecticidal activity was traced to the feces of treated insects by feeding radiolabeled material, where approximately 50% of the recovered radioactivity was unmetabolized parent compound. Ingestion of toxicant-laden feces by all life stages was evident, but the effect of this behavior was greatest on early instar nymphs. Baits containing toxicants with delayed activity, such as hydramethylnon, probably affect cockroach field populations indirectly through coprophagy.     

Feeding Behavior and Survival of Glucose-Averse Blattella germanica (Orthoptera: Blattoidea: Blattellidae) Provided Glucose as a Sole Food Source

Glucose-averse (Glu/Glu) male German cockroaches, Blattella germanica, rejected brief exposures to glucose solutions despite food deprivation so extreme as to cause high mortality. In the 24-h period following 5 days of food deprivation, both Glu/Glu and wild-type (+/+) were given a continuous source of 1 M glucose solution. Although Glu/Glu visited the solution as frequently as +/+, feeding bouts were significantly shorter. These truncated feeding bouts were sufficient to extend Glu/Glu longevity to ca. 80 days, regardless of glucose concentration. When provided continuously, the glucose was completely rejected by Glu/Glu for the first 3 days. However, by day 9, glucose intake levels were similar to those of wild-type cockroaches. The initial feeding lag probably accounted for the lower long-term survival of the Glu/Glu vs the +/+ strain. Under the stress of food deprivation, glucose-averse B. germanica modify their feeding behavior toward glucose like many phytophagous insects provided non-host plants in no-choice situations.     

德国小蠊两个海藻糖合成酶基因的克隆、组织分布及温度诱导表达分析

【目的】海藻糖合成酶（trehalose-6-phosphate synthase, TPS）是参与昆虫血糖-海藻糖合成的关键酶。本研究旨在克隆德国小蠊 Blattella germanica TPS基因,研究TPS基因在德国小蠊不同组织中的表达模式及在不同温度处理下的表达情况。【方法】通过RACE技术克隆德国小蠊TPS基因全长序列,利用荧光定量PCR的方法检测TPS基因在德国小蠊5龄幼虫不同组织中的表达模式及在高温(40℃和46℃处理30 min)及低温(0℃和10℃处理1 h)逆境下的表达量变化。【结果】从德国小蠊中克隆获得2个TPS基因,分别命名为 BgTPS1 (GenBank登录号：KR050213) 和 BgTPS2 (GenBank登录号：KR050214)。其中,BgTPS1基因cDNA序列全长2 987 bp,开放阅读框 (ORF) 2 502 bp,编码833个氨基酸;BgTPS2基因cDNA序列全长3 212 bp,开放阅读框2 469 bp,编码822个氨基酸。BgTPS1和BgTPS2基因都主要在5龄幼虫脂肪体中表达,且BgTPS2基因的表达量为BgTPS1基因表达量的3.9倍。在两种不同极端温度诱导下,BgTPS1和BgTPS2基因mRNA均上调表达。其中,BgTPS2 的表达量始终显著高于 BgTPS1。在0℃时,BgTPS1和BgTPS2的表达量最高。【结论】德国小蠊5龄幼虫中存在2个TPS基因。两个TPS基因均在脂肪体中高表达,且BgTPS2基因的表达量显著高于BgTPS1基因;低温和高温诱导下均能促进两个基因的表达量上升。该结果为进一步明确昆虫海藻糖的合成途径及其在昆虫对温度逆境的反应中的作用研究奠定了基础。     

Aspergillosis in German cockroach Blattella germanica (L.) (Blattoidea: Blattellidae)

Natural infection of Aspergillus flavus was observed in adults of Blattella germanica. Though the adult insects exhibited no external symptoms, they became hypoactive and later died. The dead and experimentally infected insects repeatedly yielded Aspergillus flavus in culture on Czapek's medium. Direct microscopic observation of the tissues of infected insects revealed fungal material. The blood films stained with Giemsa stain showed granulocytes (GRs) engulfing fungal hyphae. A remarkable increase in GR and plasmatocyte (PL) counts occurred in differential haemocyte counts (DHCs) of the infected insects. Two main types of immunological responses of the insect noticed were phagocytosis and encapsulation. DHC showed maximum involvement of GRs and PLs in immune mechanism. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agonistic Tactics and Size Asymmetries between Opponents in Blattella germanica (L.) (Dictyoptera: Blattellidae)

In this paper we investigated the influence of size differences between opponents on the occurrence of different agonistic attack and response tactics displayed during encounters between Blattella germanica (L.) cockroaches of all developmental stages, competing for a limited food source. The two main results were: 1) attack and response tactics varied during development and 2) size asymmetries between contestants influenced agonistic tactics. Developmental stage of initiator influenced the frequency distribution of the three types of attack patterns (Bite, Kick and Jump) and of the four types of response patterns (Retaliation, Escape, Resettle and No Response). The proportion of kicks increased gradually with developmental stage of the initiator whereas the proportion of bites declined during development. In addition, cockroaches adapted their attack tactics to the developmental stage of their opponent. Similarly the response displayed varied in relation to the developmental stage of the attacked individual, the developmental stage of the initiator and the type of attack displayed. During an interaction, animals appeared to be able to evaluate the relative size of their opponent and to evaluate the consequences of the behavioural pattern they displayed. Larger animals tended to minimize the intensity of the agonistic act they initiated. Escalation in interactions was rare and smaller individuals tended to escape when attacked by larger ones. Wrong estimations of the relative size of opponent, when a smaller animal retaliated after being attacked by a larger animal or when a larger animal fled after being attacked by a smaller one, represented only 6% of the records.     

Differential susceptibility of adults and nymphs of Blattella germanica (L.) (Blattodea: Blattellidae) to infection by Metarhizium anisopliae and assessment of delivery strategies

Microbial insecticides for cockroach control, such as those containing entomopathogenic fungi, may be an alternative to reduce contamination by chemicals in housing and food storage environments. Virulence of isolate ESALQ1037 belonging to the Metarhizium anisopliae complex against nymphs and adults of Blattella germanica (L.), and its infectivity following exposure of insects to a contaminated surface or to M. anisopliae-bait were determined under laboratory conditions. Estimated LD50 15 d following topical inoculation was 2.69 x 10(5) conidia per adult, whereas for nymphs the maximum mortality was lower than 50%. Baits amended with M. anisopliae conidia had no repellent effect on targets; adult mortality was inferior to 25%, and nymphs were not susceptible. All conidia found in the digestive tract of M. anisopliae-bait fed cockroaches were unviable, and bait-treated insects that succumbed to fungal infection showed a typical mycelial growth on mouthparts and front legs, but not on the hind body parts. As opposed to baits, the use of a M. anisopliae powdery formulation for surface treatment was effective in attaining high mortality rates of B. germanica. Both nymphs and adults were infected when this delivery strategy was used, and mycelia growth occurred all over the body surface. Our results suggest that the development of powders or similar formulations of M. anisopliae to control B. germanica may provide faster and better results than some of the strategies based on baits currently available.     

Response of late-instar Blattella germanica (Dictyoptera: Blattellidae) to dietary insect growth regulators

Late-instar German cockroaches, Blattella germanica (L.), were used to evaluate the relative effects of single treatments and combinations of three insect growth regulators (IGRs): pyriproxyfen, fenoxycarb, and diflubenzuron. Groups of 15 males or 15 females were held for 2 wk on food treated with varying amounts of IGRs. After removal, newly mature adults were placed with untreated adults of the opposite sex. Mortality, adult phenotype (normal wings, divergent wings, curly wings, and nymphoids), and reproduction were assessed. Mortality occurred largely in the nymphal stage except when all three IGRs were combined. Neither the average number of nymphs per egg case nor hatch of egg cases from phenotypically normal cockroaches (normal wings, occasional darkening of the body) was affected in single treatments or in combinations of two IGRs, but nymphal numbers were reduced when the three IGRs were combined. Hatch from matings of insects with divergent wings varied. At low concentrations (3-10 ppm), hatch was generally normal; at high concentrations, most mating tests were unproductive. Mating tests of cockroaches with curly wings were almost always unproductive. When males with curly wings were mated, females dropped either unfertilized egg cases (no mating) or partially fertilized egg cases. Curly-wing females either dropped unfertilized egg cases or failed to form egg cases because of deleterious effects on ovarian development. Nymphoids did not mate. Diflubenzuron at 100 ppm had no effect other than causing the appearance of a few insects with divergent wings. Effects on phenotype and reproduction began at 3 ppm of both pyriproxyfen and fenoxycarb and at a comparable concentration in the combination of pyriproxyfen + fenoxycarb (1 ppm each). Female sterility was complete at 100 ppm of pyriproxyfen and fenoxycarb. When pyriproxyfen or fenoxycarb was combined with equal amounts of diflubenzuron, the number of productive matings was not reduced at 6 ppm (3 ppm per each IGR). At 20 ppm (10 ppm per each IGR), a reduction in productive matings coincided with the appearance of curly wings. Complete female sterility occurred only at 600 ppm (300 ppm per IGR). The most severe effects occurred in the experiment with equal amounts of pyriproxyfen, fenoxycarb, and diflubenzuron. In addition to reduced hatch from normal phenotypes, this experiment caused complete male sterility (300 ppm; 100 ppm of each IGR). Female sterility was complete at greater than or equal to 90 ppm (30 ppm of each IGR).     

Monitoring for insecticide resistance in field-collected populations of Blattella germanica (Blattaria: Blattellidae)

Seven field-collected populations of German cockroach, Blattella germanica (L.) (ICN, DNH, CHN, DGU, BSN, GSN, and GWJ), were tested for susceptibility to eight different insecticides by a topical application method, and were compared to an insecticide-susceptible KSS strain. Marked regional variations of insecticide susceptibility were observed. Extremely high to high levels of resistance were observed in bifenthrin [resistance ratio (RR), 46–159], deltamethrin (RR, 61–160), and esfenvalerate [RR, 70–270; except for BSN females (RR, 20) and GSN females (RR, 24)]. Low to moderate levels of resistance were observed in cypermethrin [RR, 16–29; except for DGU females (RR, 88) and BSN females (RR, 41)], permethrin [RR, 11–39; except for DNH females (RR, 110) and BSN females (RR, 44)], chlorpyrifos [RR, 2–13; except for GSN and GWJ females (RR, ca. 140)], chlorpyrifos-methyl (RR, 2–8), and fenthion (RR, 8–17). All of the colonies were susceptible to one or more of the insecticides examined. These results indicate that careful selection and rotational use of these insecticides should result in continued satisfactory control against field populations of German cockroach.     

Fine Structure of the Fat Body and its Bacteroids in Blattella germanica (Blattodea)

The abdominal fat body of the cockroach Blattella germanica contains three characteristic cell types—trophocytes, bacteriocytes and urate cells—which have been investigated by electron microscopy. The trophocytes are rich in lipid droplets of different sizes; glycogen, rough endoplasmic reticulum and mitochondria are also abundant. In females immediately after eclosion, the trophocytes contain a greater number of lipid droplets, some of which have different electron density; glycogen and cytoplasmic organelles are clearly reduced. The bacteriocytes hold rod-like and spherical bacteroids, which are encapsulated by a vacuolar membrane; they show a thin cytoplasmic membrane and an evident cell wall surrounded by a membrane-like outer envelope. The bacteroids appear to be dividing either by transverse partition or by budding. The urate cells, adjacent to the bacteriocytes, are characterized by complex urate vacuoles delimited by a double layer-structure.     

Effects of the synergists piperonyl butoxide and S,S,S-tributyl phosphorotrithioate on propoxur pharmacokinetics in Blattella germanica (Blattodea: Blattellidae).

Effects of the synergists piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) on propoxur pharmacokinetics were examined in the German cockroach, Blattella germanica (L.). Treatment of adult male German cockroaches with the cytochrome P450 monooxygenase inhibitor, PBO, or the esterase inhibitor, DEF, increased propoxur toxicity by 2- and 6.8-fold, respectively, implicating hydrolysis as a major detoxification route of propoxur in the German cockroach. However, significant hydrolytic metabolism could not be demonstrated conclusively in vitro resulting in a conflict between in situ bioassay data and in vitro metabolic studies. In vitro propoxur metabolism with NADPH-fortified microsomes produced at least nine metabolites. Formation of metabolites was NADPH-dependent; no quantifiable metabolism was detected with cytosolic fractions. However, microsomal fractions lacking an NADPH source did produce a low, but detectable, quantity of metabolites (1.6 pmol). PBO inhibited NADPH-dependent propoxur metabolism in a dose-dependent fashion, implicating cytochrome P450 monooxygenases as the enzyme system responsible for the metabolism. Interestingly, DEF also inhibited the NADPH-dependent metabolism of propoxur, albeit to a lower extent. Treatment with PBO or DEF also caused a significant reduction in the cuticular penetration rate of propoxur. The data demonstrate that unanticipated effects are possible with synergists and that caution must be exercised when interpreting synergist results.     

Isolation and sequence of a partial vitellogenin cDNA from the cockroach,Blattella germanica (L.) (Dictyoptera,Blattellidae), and characterization of the vitellogenin gene expression

A partial cDNA clone of the vitellogenin gene from the cockroach Blattella germanica has been isolated from a cDNA expression library using an anti-vitellin–vitellogenin antiserum probe. The analysis of cDNA inserts gave a sequence of 2,645 nucleotides corresponding to the 3′ region. The deduced amino acid sequence is 825 residues long and is similar to the homologous portion of the vitellogenin of other insect species, especially that of the mosquito Aedes aegypti. RNA hybridization studies indicated that the vitellogenin gene expression is limited to the fat body of adult females. The pattern of expression during the first vitellogenic cycle was approximately parallel to that of vitellogenin production by the fat body previously described. The availability of a cDNA probe for the B. germanica vitellogenin gene represents a useful tool to study the molecular action of hormones affecting vitellogenin synthesis in this species. Arch. Insect Biochem. Physiol. 38:137–146, 1998. © 1998 Wiley-Liss, Inc.     

Comparisons of toxic baits for controlling the cockroach, Blattella germanica: attractiveness and feeding stimulation

Female German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae) and nymphs (stages 1, 3 and 6) were used to test the attractiveness and the feeding stimulation of several commercial gel formulations of insecticide food baits in laboratory binary choice tests. The four toxic gel baits tested were: 'Avert' (0.05% abamectin=avermectin B1), 'Drax' (33.3% boric acid), 'Goliath' (0.05% fipronil) and 'Maxforce' (2.15% hydramethylnon). The attractiveness of a bait was estimated by the number of cockroaches that chose it first, and by their tendency to change to it secondarily. Feeding stimulation was estimated by the mean duration of feeding bouts and total duration of food intake. Variability of these factors was assessed in relation to age of cockroaches and to age of baits. With a few exceptions, cockroach age did not affect performance in any of these tests. Attractiveness to B. germanica ranked 'Goliath' gel higher than 'Avert', 'Drax' and 'Maxforce' gels, whether or not the active ingredient fipronil was present in 'Goliath' gel. Feeding stimulation ranked 'Avert' and 'Maxforce' gels higher than 'Goliath' gel, and 'Drax' gel was inferior. With ageing up to 3 months, the feeding stimulation power of 'Goliath' and 'Maxforce' gels increased, whereas that of 'Avert' fluctuated. Assuming that all types of bait effectively kill cockroaches once ingested, these results illustrate the importance of behavioural observations on bait efficiency and show that ranking of these different food baits varies in relation to the parameter analysed.     

Biochemistry and regulation of pheromone production in Blattella germanica (L.) (Dictyoptera,Blattellidae)

Females of the German cockroach, Blattella germanica, produce a contact sex pheromone consisting of the methyl ketones 3,11-dimethyl-2-heptacosanone, 3,11-dimethyl-2-nonacosanone, 29-hydroxy- and 29-oxo-3,11-dimethyl-2-nonacosanone. We review evidence in support of the hypothesis that in adult females the hydrocarbon 3,11-dimethylnonacosane is oxidized to the corresponding methyl ketone pheromone. Recent studies on the precursors and directionality of synthesis of the methyl-branched alkane indicate that it is formed by the insertion of methylmalonyl units derived from propionate, isoleucine, valine, methionine and succinate early in chain elongation. The hydrocarbon is then hydroxylated and oxidized at the 2-position to form the methyl ketone pheromone. The in vivo synthesis of pheromone and its accumulation on the cuticle are correlated to the synthesis of juvenile hormone (JH) by the corpora allata (CA) in vitro and to oocyte development, suggesting common regulation by JH of pheromone production as well as other reproductive events. The patterns of pheromone and hydrocarbon production in starved, allatectomized and head-ligated females, as well as in females rescued with hormone-replacement therapy, suggest two mechanisms of regulation of pheromone production: a JH-induced conversion of hydrocarbon to pheromone is related to the CA cycle and to oocyte development, while a JH-independent mechanism, which is probably related to feeding, supplies precursors for hydrocarbon biosynthesis.     

Olfactory conditioning with single chemicals in the German Cockroach, Blattella germanica (Dictyoptera: Blattellidae)

Many insects find resources by means of the olfactory cues of general odors after learning. To evaluate behavioral responses to the odor of a particular chemical after learning with reward or punishment quantitatively, we developed a standardized odor-training method in the German cockroach, Blattella germanica (Linnaeus), an important urban pest species. A classical olfactory conditioning procedure for a preference test was modified to become applicable to a single odor, by which a (?)-menthol or vanillin odor was independently associated with sucrose (reward) or sodium chloride solution (punishment). The strength of the association with the odor was evaluated with the increase or decrease in visit frequencies to the odor source after olfactory conditioning. The frequency increased after (?)-menthol was presented with a reward, while it did not change with the rewarded vanillin odor. With both odors, the frequency decreased significantly after training with a punishment. These results indicate that cockroaches learn a single compound odor presented as a conditioned stimulus, although the association of the odor with a reward or punishment depends on the chemical. This olfactory conditioning method can not only facilitate the analysis of cockroach behavior elicited by a learned single chemical odor, but also quantify the potential attractiveness or repellency of the chemical after learning.     

Monitoring pyrethroid resistance in field collected Blattella germanica Linn. (Dictyoptera: Blattellidae) in Indonesia

The German cockroach, Blattella germanica , is a major and the most common pest in public areas in Indonesia. Although intensive control measures have been carried out to control the populations of this pest, results have been far from successful, which is believed to be because of its resistance to insecticides. A standard World Health Organization (WHO) glass jar test was carried out to determine the resistance level of this insect to pyrethroid insecticides, the most commonly used insecticides for cockroach control in Indonesia. A susceptible S1 strain collected from Tembagapura Papua was compared with four strains collected from Bandung, West Java: strain S2, from a local restaurant; strain S3, from the Bandung train station; and strains S4 and S5, from two different hotels. All strains showed low resistance to the pyrethroid, except the S5 strain, which had a Resistance Ratio (RR)₅₀ of 95 for permethrin. The addition of piperonyl butoxide (PBO) suggests that the detoxifying enzyme mixed function oxidases (MFO) played an important role in the development of resistance to permethrin in the S5 strain, suggested by the high Synergist Ratio (SR) of 70.4. However, the low level of resistance to cypermethrin was not affected by PBO, suggesting that other mechanisms of pyrethroid resistance are involved. Our study is the first report of German cockroach resistance to permethrin in Indonesia, and the findings can be used in formulating potential strategies for cockroach resistance management.