Oriental Cockroach Blatta Orientalis Research Articles

Isolation and Identification of Shimwellia blattae from the Gut of the Hospital Cockroach Blatta orientalis in Annaba City, Algeria

The overall aim of this paper was to divulge the pathogenic and beneficial bacterial flora of cockroaches (Blatta orientalis) living in a hospital area in Annaba city, Algeria. Thirteen cockroaches were randomly apprehended in sterile conditions during March 2022 in two different hospitals in Annaba, “El Bouni” Hospital and the “Sainte-Therese” Hospital. Bacterial strains were isolated from the imprint of the insect on Petri dishes previously inoculated with different media, also from external and internal body part suspensions of the captured specimens. Biochemical identification was established using the analytical profile Index (API) System (Biomerieux, France). The identification of the enteric-screened strain was confirmed using molecular sequencing of the 16S rRNA gene and phylogenetic analysis was performed. The results showed a high prevalence of the pathogenic strains isolated from the oriental cockroach Blatta orientalis (225 strains), such as Serratia liquefaciens, Raoultella ornithinolytica, Pseudomonas luteola, Enterobacter aerogenes, Hafniaalvei and Bacillus sp. Phylogenetic analysis of the enteric bacteria confirmed the affiliation with Shimwellia blattae NCTC10965 (100%), Basonym Escherichia blattae, which is a natural cyanocobalamin producer. Results confirm at the same time the symbiotic relationship between S. blattae and Blatta orientalis, but also point out the underrepresented potential of these insects as a source of strains with biotechnological interest.

Disease prevalence in an urban raptor related to pest species: The case of Eurasian Scops Owl Otus scops infection by Gongylonema sp.

Urbanization is often associated with homogenization, including the homogenization of biodiversity and overpopulation by generalist species that can change community and disease dynamics. In Madrid, nestlings of Eurasian Scops Owl Otus scops frequently suffer necrotic oropharyngeal disease as a result of infection by Gongylonema sp., a parasitic nematode transmitted by adult owls to their offspring through the diet, more specifically through consumption of a pest species: the oriental cockroach Blatta orientalis. We studied how the presence of cockroaches and owl infection rates are affected by urban features such as green areas. We found that a higher number of birds were affected by the parasite in the initial period of the breeding season and in areas with greater surface area of green spaces. We suggest that urban management should promote the diversity of insects in green areas so that the owls diversify their dietary offer to their offspring, to reduce the prevalence of the disease and improve their breeding success in the city of Madrid, as this problem has not yet been described in other cities.

The Oriental Cockroach Blatta orientalis L. Recovered from Early Roman London: Implications for Past Distribution and Roman Trade

ABSTRACT This paper describes the recovery and identification of oothecae of the oriental cockroach (Blatta orientalis L.) from deposits associated with an Early Romano-British bakery oven from Roman Londinium (now modern-day London). The ecology, behaviour and past archaeological history of this species are presented. The implications of finding this species for our understanding of the movement and importation of stored products and other materials by the Roman Army and citizenry is outlined.

Eating in a losing cause: limited benefit of modified macronutrient consumption following infection in the oriental cockroach Blatta orientalis

BackgroundHost–pathogen interactions can lead to dramatic changes in host feeding behaviour. One aspect of this includes self-medication, where infected individuals consume substances such as toxins or alter their macronutrient consumption to enhance immune competence. Another widely adopted animal response to infection is illness-induced anorexia, which is thought to assist host immunity directly or by limiting the nutritional resources available to pathogens. Here, we recorded macronutrient preferences of the global pest cockroach, Blatta orientalis to investigate how shifts in host macronutrient dietary preference and quantity of carbohydrate (C) and protein (P) interact with immunity following bacterial infection.ResultsWe find that B. orientalis avoids diets enriched for P under normal conditions, and that high P diets reduce cockroach survival in the long term. However, following bacterial challenge, cockroaches significantly reduced their overall nutrient intake, particularly of carbohydrates, and increased the relative ratio of protein (P:C) consumed. Surprisingly, these behavioural shifts had a limited effect on cockroach immunity and survival, with minor changes to immune protein abundance and antimicrobial activity between individuals placed on different diets, regardless of infection status.ConclusionsWe show that cockroach feeding behaviour can be modulated by a pathogen, resulting in an illness-induced anorexia-like feeding response and a shift from a C-enriched to a more P:C equal diet. However, our results also indicate that such responses do not provide significant immune protection in B. orientalis, suggesting that the host’s dietary shift might also result from random rather than directed behaviour. The lack of an apparent benefit of the shift in feeding behaviour highlights a possible reduced importance of diet in immune regulation in these invasive animals, although further investigations employing pathogens with alternative infection strategies are warranted.

New insights into predation through imaging

ABSTRACT The role of generalist predators has long been considered an important component of mortality for many agricultural pests but can be difficult to quantify. We present the use of digital imaging as a means of both identifying key stink bug egg predators and measuring their relative impact on egg survivorship. Brown marmorated stink bug (BMSB), Halyomorpha halys and bagrada bug, Bagrada hilaris, two exotic stink bugs new to California, are now widely distributed throughout the state. A survey was conducted to identify resident natural enemies of their eggs. A field camera aided in the identification of arthropods attacking these eggs and their relative impact. Predation of BMSB eggs, which are naturally oviposited onto plant foliage, was less than for eggs of bagrada bug, which oviposit onto and into soil. The top ranked predators of BMSB eggs were the carabid Laemostenus complanatus (Coleoptera) the European earwig Forficula auricularia and ring-legged earwig Euborellia annulipes (Dermaptera), the oriental cockroach Blatta orientalis (Orthoptera), and the spider Trachelas spp. (Araneae). The two most common and important predators of bagrada bug were two ant species (Formicidae), Solenopsis xyloni and Monomorium ergatogyna, and species of Collembola (Entomobryidae). A Predation Index was developed to compare the relative importance of BMSB egg predators. Lastly, two striking, unanticipated results are reported: an apparent synergistic interaction between the spider Trachelas spp. and native ant M. ergatogyna in causing damage to sentinel eggs of BMSB, and the predaceous role for Collembola on bagrada bug sentinel eggs.

Nymphs of the Oriental cockroach (Blatta orientalis) as passive vectors of causal agents of avian tuberculosis and paratuberculosis.

The potential transmission of the causal agent of paratuberculosis Mycobacterium avium ssp. paratuberculosis and avian tuberculosis Mycobacterium avium ssp. avium (Actinomycetales: Mycobacteriaceae) by nymphs of the Oriental cockroach Blatta orientalis L. (Blattodea: Blattidae) was investigated by oral infection with mycobacterial suspensions and examination of their droppings and bodies. Both the subspecies of M. avium were isolated from droppings at 3 days post-infection and M. a. avium was found in homogenized bodies at 10 days post-infection. The identity of M. a. avium and M. a. paratuberculosis isolates was demonstrated by Restriction Fragment Length Polymorphism (RFLP) analysis. The M. a. avium isolate used as the inoculum and the isolates from the bodies and droppings of the nymphs were shown to be virulent in chickens. The results show that orally infected nymphs of B. orientalis can harbour and shed viable and virulent mycobacteria. This hazard should be considered in the implementation of control measures against mycobacterial infections of animals and humans, which should include destruction of all developmental stages of cockroaches and prevention of their access to materials that can be contaminated by mycobacteria.

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An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

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An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

Table of Contents

An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

Cover 2 - Editorial Board

An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

Cover 2 - Editorial Board

An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

Cover 2 - Editorial Board

An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

Effect of carbon dioxide on the Oriental cockroach Blatta orientalis.

Exposure to high concentrations of carbon dioxide (CO2) killed adult and nymphal stages of the oriental cockroach Blatta orientalis L. (Dictyoptera: Blattidae) with LT50 values of 11.5-16.2 h for 60% CO2 in air and 5.7-7.1 h for 100% CO2 at 20 degrees C; corresponding LT50s at 28 degrees C were 2.8-4.6 h for 60% CO2 in air and 2.3-3.6 h for 100% CO2. Complete kill of mobile stages was obtained within 24 h using 60% CO2 at 20 degrees C. Survivors of treatments with 100% CO2 at 28 degrees C remained completely paralysed for up to 3 days post-treatment and took up to 5 days to regain normal movement, but adult females then resumed production of oothecae with no significant loss in fecundity. Oothecae 5 or 30 days after deposition required 60-84 h exposure to 60% CO2 at 20 degrees C to prevent emergence of nymphs but less time using 100% CO2 at 28 degrees C. At 28 degrees C, when adult females were treated with 100% CO2 and 52% r.h. for 6 h (giving 100% mortality) loss of weight was significantly greater than that following treatment with air at 52% r.h. for 6 h (giving no mortality). However, significantly greater weight loss also occurred when they were treated with dried air (< 10% r.h.) for 6 h, also with no mortality. The toxicity of CO2 to mobile stages of the oriental cockroach appeared to result from irreversible effects on the nervous system, rather than from water loss during exposure.

Light and Electron Microscopic Study of a Rickettsiella Species from the Cockroach Blatta orientalis

An infection with Rickettsiella sp. was responsible for an illness causing heavy body swelling in the Oriental cockroach Blatta orientalis. Reproduction of the colony stagnated. Vacuoles with parasitic bacteria occurred mainly in the fat body, but also in nearly all other organs, such as gut epithelium, Malpighian tubules, blood cells, and ovarioles. The parasites clearly differed from the symbiotic bacteria of the genus Blattabacterium, which regularly occur in the mycetocytes of B. orientalis. The vacuoles contained four stages of Rickettsiella: (1) infectious, electron-dense, rod-like elementary bodies (mean size 300 × 145 nm); (2) an electron-dense, flat intermedium stage, called flat body (mean size 515 × 255 × 125 nm); (3) an electron-light, spherical intermedium stage, called condensing sphere (mean size 340 nm); portions of cytoplasm condensed crescent-like at the border or in the center of the cell; and (4) large, spherical, electron-light initial bodies that multiplied by binary fission (mean size 600 nm). The initial bodies had a three-layered cell boundary, but all other stages had a five-layered cell boundary. Elementary and flat bodies contained an electron-light, oblique lamella and an oval structure with an array of ribosome-like granules, respectively. In contrast to other species of Rickettsiella, crystal formation or multiple division did not occur. The described species of Rickettsiella is different from “R. blattae,” which belongs to the R. popilliae group. Instead, it shares more similarities with the R. chironomi group. To avoid confusion, it was provisionally named “R. crassificans.”

Effect of arena size on behaviour and mortality of the oriental cockroach Blatta orientalis in arenas with a cypermethrin deposit adjacent to harbourage access points.

Activity and survival of adult female Blatta orientalis was investigated using tagged cockroaches in periodically illuminated arenas (LD 12:12 h) with a harbourage at one end. The arenas were rectangular with a width of 50 cm and lengths up to 480 cm. A cypermethrin-treated plywood plate (50 x 11 cm) substrate across the harbourage access points caused cockroaches to be exposed to the insecticide deposit by tarsal contact as they entered or left the harbourage. The effects of varying arena length and cypermethrin concentration were tested at 28 degrees C. The LC50 following 3 days exposure ranged from 5.7 to 11.8 mg/m2 on the plywood plate for arena lengths of 60 to 480 cm, respectively; cypermethrin at 30 mg/m2 produced 100% knockdown of B. orientalis within one 12 h dark period. During darkness, active cockroaches spent most time close to the harbourage or around food and water stations, at the far end of the arena, and made frequent returns into the harbourage. For arena length 120 cm, the mean duration of contact with treated plates during the first hour of the dark period was significantly less than contact time on untreated plates, but during 12 h the cumulative contact times were not significantly different between treated and untreated plates. During the first 4 h of the dark period, mean cockroach numbers on the treated plate declined as arena length increased, but not as rapidly as the mean number/unit area over the rest of the arena. The arena design is considered suitable for comparative testing of fast-acting neuroactive insecticide deposits against cockroaches.

The effects of the insect growth regulator lufenuron on oriental cockroach, Blatta orientalis, and german cockroach, Blattella germanica, populations in simulated domestic environments

AbstractBait (50 mg AI kg−1) and spray (10 mg AI m−2) formulations of the novel insect growth regulator (IGR) lufenuron were tested against populations of the Oriental cockroach Blatta orientalis L. and the German cockroach Blattella germanica L. that had been established in simulated domestic environments. The treated populations of B. germanica declined rapidly three to four months after the start of bait or spray treatment, and were completely eradicated after 12 months. As well as disrupting the moulting process, lufenuron affected the reproduction of B. germanica by preventing the hatch of the oothecae. In B. germanica, it appeared probable that lufenuron was transferred from female cockroaches to the oothecae while they were being carried. By contrast with B. germanica, the treated populations of B. orientalis did not show any substantial decline compared with the control, even after 18 months' exposure to lufenuron bait or spray treatments. Moreover, neither moulting nor reproduction in the populations of B. orientalis appeared to be affected by either of the lufenuron treatments. Subsequently, laboratory investigations with surface deposits of either technical or formulated lufenuron, applied at dose rates up to 50 mg AI m−2, failed to demonstrate any significant effects on the development or reproduction of B. orientalis. Laboratory tests with first‐instar nymphs of both species revealed substantial differences in sensitivity to the moult‐disrupting effects of the compound. These differences extended to the adult insects, where reproduction was markedly affected in B. germanica, but apparently unaffected in B. orientalis. Thus, both bait and spray formulations of lufenuron have been shown to provide rapid and effective control of German cockroach populations in simulated domestic environments. However, the same treatments were much less effective against similar populations of the Oriental cockroach. These results are discussed in terms of the potential effectiveness of lufenuron as a cockroach control agent, and in relation to the substantial differences in susceptibility to the inhibitory effects of this compound on reproduction that were apparent between Blatta orientalis and Blattella germanica.

Effects of hydroprene on development and reproduction in the Oriental cockroach, Blatta orientalis.

Nymphs of the Oriental cockroach Blatta orientalis were exposed during the penultimate and final instars to vinyl tiles treated with the juvenile hormone analogue hydroprene. Adults moulting from these nymphs exhibited deformities such as twisted wings in both sexes and modified genitalia in females. Females with deformities were unable to produce viable oothecae. B.orientalis confined on tiles treated with hydroprene at rates of 25-100 mg/m2 did not reproduce. The treatment rate of 10 mg/m2 reduced fecundity and caused 47-57% of resultant adults to have deformities, but some adults reproduced successfully and population growth was not suppressed.

Reproductive and developmental biology of the oriental cockroach Blatta orientalis (Dictyoptera)

At 27 degrees C and 45% r.h. in the laboratory, the oriental cockroach Blatta orientalis (L.) developed to adulthood in seven to nine instars for males (66% had eight instars) and eight to ten instars for females (67% had nine instars) in mixed groups, with up to twelve instars for isolated females. Nymphal development lasted 185 +/- 2 days for males, 216 +/- 4 days for females, with 89% survival to adulthood. Adult longevity was significantly more for males than females in mixed groups. Virgin females lived for 135 +/- 6 days compared with 87 +/- 9 days for females kept with males. After an initial maturation time of 12.2-13.5 +/- 0.4 days for mated and unmated females, oothecae were produced, on average, every 6-7 (range 2-29) days. Ootheca viability was 68% from females kept with males, 32% from females kept apart from males. Numbers of nymphs emerging were 14.1 +/- 0.26 after 45 days from mated female oothecae 8.2 +/- 0.3 after 49 days from unmated females. With sexual reproduction the sex ratio of progeny reaching adulthood was 1.1 males per female (n = 443), whereas unmated females produced only female progency, which is consistent with parthenogenetic reproduction. Drawings of the ventral aspect of the terminalia are given to show features useful for instar determination and for distinguishing between male and female nymphs and adults of B. orientalis.

Distribution of Oriental and German cockroaches, Blatta orientalis and Blattella germanica (Dictyoptera), in the United Kingdom

Results are presented of a survey carried out by Rentokil Ltd on the distribution of the Oriental cockroach Blatta orientalis L. and the German cockroach Blattella germanica L. in the United Kingdom. The known ranges of both species are increased considerably by the findings of the survey, with several new vice-county records for Scotland (including the Western Isles), England and Wales. The frequency at which Blatta orientalis was observed in outdoor habitats may indicate that this species sometimes spreads to new areas without human assistance.

Spectral sensitivity of visual cells of the compound eye ofBlatta orientalis

Responses of single visual cells of the anterior part of the compound eye of the oriental cockroachBlatta orientalis were recorded intracellularly. Two spectral types of cells were discovered: ultraviolet receptors with λmax 361 nm and green-sensitive receptors with λmax 503 nm. The spectral curve of the whole eye, measured by the electroretinogram, included two peaks (λ=350−370 and 500 nm) and a minimum between 400 and 430 nm. This last fact is interpreted as additional evidence of the dichromatic vision of the cockroach.