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.

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 biosynthesis of (+)- -pinene in Pinus species.

1. The degradation of (+)-alpha-pinene biosynthesized from 3RS-[2-(14)C]mevalonate by Pinus radiata or Pinus nigra revealed an asymmetrical labelling pattern whereby the moiety derived from isopentenyl pyrophosphate contained at least 90% of the incorporated tracer. This pattern differed both in asymmetry and position of labelling from previous results obtained with P. nigra, but is consistent with the generally accepted hypothetical mechanism for the biosynthesis of the pinane skeleton. 2. (+)-alpha-Pinene biosynthesized in Pinus attenuata and in the previously named two species from 3RS-[2-(14)C,(4R)-4-(3)H(1)]mevalonate and its (4S)-isomer retained all the 4R hydrogen atoms (within the experimental error) but lost all the 4S hydrogen atoms of the precursor. This stereospecificity of hydrogen loss is the same as that previously found for the formation of geraniol and nerol in other plant species, and the result may be reasonably inferred to be general for monoterpenes.