Toxicity of phosphine to the diapausing stages of Ephestia elutella, Plodia interpunctella and other lepidoptera

Diapausing larvae of the stored product moths Ephestia elutella (Hübner) and Plodia interpunctella (Hübner) were tolerant of phosphine only in short exposures, the tolerance of E. elutella being at least twice that of P. interpunctella. The tolerance of a freshly collected wild stock of each species was, at some temperatures, about two or three times that in a laboratory reared stock. The wild stock of E. elutella required concentration-time (CT) products of 36 mg hr/l in 4-day exposures at 10° and 15°C, and 18 mg hr/l in 2-day exposures at 20°C and above for 100% kill. The tolerance of E. elutella larvae in diapause was not dependent on the manner in which diapause was induced, maintained or subsequently terminated. Longer exposures to phosphine were more effective than shorter ones of similar CT product because an initial period of about a day in each exposure was required for insects in diapause to be killed. At 25°C, a concentration of 0.03 mg/l was below the threshold level for mortality of some larvae, long exposures at such very low concentrations proving ineffective.

Diapausing pupae of an outdoor species, Pieris brassicae (L.), and eggs of the univoltine race of Bombyx mori (L.) were highly tolerant of phosphine at 10°C.     

Development of Ephestia kuehniella (Zeller), Plodia interpunctella (Hübner) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) on kernels and wholemeal flours of Fagopyrum esculentum (Moench) and Triticum aestivum L.

Three stored product moth pests, Ephestia kuehniella, Plodia interpunctella and Corcyra cephalonica were reared on the following five foods: whole buckwheat with pericarp, decorticated buckwheat, wheat var. “Centauro” (kernels), wholemeal wheat flour and whole buckwheat flour. Results showed that achenes of buckwheat with pericarp are a poor food for the development of these species. A low rate of survival to adulthood for E. kuehniella and P. interpunctella was recorded, with a considerable extension of post-embryonic development. Although the mandibles of larvae are strong, they have trouble in breaking the fibrous buckwheat pericarp. It was observed that when the seed was decorticated there was a higher percentage of adults emerged. The emergence of E. kuehniella began, according to the food given, 34–42 days after the eggs were laid. The susceptibility index (s.i.) of achenes without pericarp (s.i. 9.7) was higher than that observed on wheat (s.i. 8.6). The first P. interpunctella adults were found after 29 days on wheat and after 56 days on buckwheat with pericarp. The shortest mean period of development occurred on wheat (34 days) while the longest was on buckwheat with pericarp at 81 days. The highest susceptibility index was on kernels (s.i. 12.8), the lowest one was on buckwheat with pericarp (s.i. 2.3). C. cephalonica began to emerge, according to the food given, after 40–55 days. In this case, fewer adults were recorded from buckwheat with pericarp, but no significant differences among the means of emerged adults on wheat, wholemeal wheat flour and whole buckwheat flour were observed. The longest mean period of development was recorded on wholemeal wheat flour (72 days) while the shortest was on wheat kernels (58 days). The highest value for the susceptibility index was obtained for wheat kernels (s.i. 7.4) and the lowest one for buckwheat with pericarp (s.i. 4.5).     

低温冷藏对烟草粉螟亲代和子代适合度的影响

为明确低温冷藏对烟草粉螟亲代和子代适合度的影响,根据年龄-龄期两性生命表理论,对5℃冷藏160d后的烟草粉螟5龄幼虫亲代生殖适合度及其子代发育历期、存活率、繁殖率和种群参数进行研究。结果表明,低温冷藏160d后烟草粉螟F₀代的蛹期显著长于对照,雌雄成虫寿命、平均繁殖力和产卵时间均显著低于对照;但在F₁代中,除了低温处理的平均繁殖力（148.29粒）显著高于对照（113.93粒）外,其他参数均无显著差异。研究表明,低温冷藏显著降低烟草粉螟亲代的适合度,对子代的适合度则无显著影响。     

Supercooling point variability in the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Factors affecting the supercooling point (SCP) of the Indian meal moth, Plodia interpunctella (Hübner), were investigated under various conditions. The effects of geographic origin, time under laboratory conditions, laboratory diet, stage of development, age within stage, and season on P. interpunctella SCP were examined. Overall, SCPs ranged from −28.6 to −2.4 °C. At the times of collection, differences in SCP between field-collected individuals and individuals from laboratory sources were negligible. The minimum observed SCP for most of the cultures tested soon after collection was below −20 °C. After 7 months under laboratory conditions, the mean SCP of field-collected and laboratory-reared cultures remained unchanged. No particular trend in SCP was observed when comparing cultures from northern and southern regions. Differences in laboratory diets did not affect mean SCP. Mean SCP for 1- and 4-d-old eggs was similar. Eggs (−24.4 °C), first instars (−23.5 °C), pupae (−22.2 °C), and adults (−22.4 °C) had lower mean SCPs than later instar larvae (−14.4 to −11.6 °C). When confined in the laboratory for 8 months under conditions which were not controlled, monthly mean SCP for the same culture varied by as much as 5.7 °C. Plodia interpunctella appeared to regulate its SCP as the season changed, with a relatively high mean SCP during summer and a marked decline of more than 10 °C in fall. The SCPs obtained in this study suggest that very low temperatures may be needed for disinfestation of P. interpunctella at all stages of development.     

A wild strain of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) from farm-stored maize in South Carolina: Effect of temperature on mating, survival, and fecundity

The purpose of this study was to develop age-specific survivorship and fecundity schedules for adult Plodia interpunctella (Hübner) relevant to maize storages, with special reference to the southeastern states (USA). Laboratory cultures were established with moths collected from farm-stored maize in South Carolina and maintained on cracked maize at 30 °C and 60% r.h. Age-specific schedules of survivorship and fecundity, the length of the oviposition period, mating success, and mating frequency were determined at 20, 25, 30, and 35 °C and about 75% r.h. The maximum oviposition period was longest (18 d) at 20 and 25 °C, and shortest (8 d) at 35 °C. The optimum temperatures for reproduction (mating frequency and fecundity) were 25–30 °C, but mean life-span was longest (13.2 d) at 20 °C and declined linearly with increasing temperature. Mean total (lifetime) fecundity ranged from 16.9 eggs at 35 °C to 227.7 eggs at 25 °C.     

Technologically important characteristics of Enterococcus isolates from milk and dairy products

Enterococcus faecium (54 strains), E. faecalis (40 strains), and E. durans (14) were isolated from various dairy products (raw milk, cream, butter and fermented milk products) during a previous study (Wessels et al., 1988). In this article various characteristics of these isolates, which may have a bearing on their significance in dairy products, have been studied. A large percentage of the identified strains of all three species were able to grow at 7°C. Seventy-six percent of the E. faecium strains, 62% E. faecalis and 50% E. durans strains also showed proteolytic activity at psychrotrophic temperatures. The fact that proteolytic activity could be detected within 2 days at 7°C is significant, since bulk cooled milk is normally held for 3 to 4 days at temperatures between 4 and 7°C at farms or factories prior to processing. This examination confirmed that enterococci are proteolytic rather than lipolytic.     

Simulation studies on the effects of solar heat on egg-laying, development and survival of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) in stored bambara groundnut Vigna subterranea (L.) Verdcourt

The effects of simulated solar heat on oviposition, development and survival of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) in stored bambara groundnut, Vigna subterranea (L.) Verdcourt, were evaluated at three high temperatures (40°C, 45°C and 50°C) at a constant, low humidity (30% relative humidity). Exposure to these temperatures for 6 h significantly reduced oviposition in C. maculatus and C. subinnotatus females. Females of both species that were exposed to 50°C laid significantly fewer eggs than those exposed to 40°C; and in the case of C. maculatus, females exposed to 45°C also laid significantly fewer eggs than those exposed to 40°C. The percentage of eggs laid by females of both species that reached adulthood after exposure to 50°C for 2–6 h was significantly lower than the percentage that developed from eggs laid by females that were exposed to 40°C. No adult developed from eggs of C. maculatus exposed for 6 h at 50°C or from eggs of C. subinnotatus exposed for 2 h at this temperature. For both species, no adult progeny subsequently emerged from seeds harbouring first instar larvae when exposed at 50°C for 2, 4 or 6 h. Older larvae of C. maculatus were more tolerant of exposure at 50°C: 26.8, 10.2 and 0.9% of late instar larvae exposed for 2, 4 and 6 h, respectively, developed to the adult stage. In contrast, no adults of C. subinnotatus emerged from seeds harbouring late instar larvae when exposed at 45°C for 6 h nor in seeds exposed to the temperature of 50°C for 4 or 6 h. On average, immature stages of C. subinnotatus were more susceptible to heat treatment than those of C. maculatus.     

Life history of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) at optimum conditions of temperature and humidity

At 32°C, 80% r.h. the mean egg, larval and pupal development periods of Prostephanus truncatus (Horn) were 4.86, 25.40 and 5.16 days, respectively. After a pre-oviposition period of 5–10 days, female adults laid most eggs at 15–20 days old and some continued to lay eggs for a further 70–80 days. Mean total egg production was 50 eggs per female and the maximum number of eggs laid in a 5-day period by a single female was 33. On average, 68.4% of all eggs were found inside damaged grains.

Mean adult longevity was 44.7 days for males and 61.1 days for females but these were not significantly different due to high variability in the data. P. truncatus was found to have a finite rate of natural increase (λ) of 1.399 per week and an infinite rate of increase (r) of 0.336 per week.     

The toxicity of phosphine to all developmental stages of thirteen species of stored product beetles

The toxicity of phosphine to all stages of 13 species of stored product beetles was determined using large numbers of test insects which made possible more accurate assessments of mortality. Species tested were Acanthoscelides obtectus, Caryedon serratus, Cryptolestes ferrugineus, C. pusillus, Lasioderma serricorne, Oryzaephilus surinamensis, Ptinus tectus, Rhyzopertha dominica, Sitophilus granarius, S. oryzae, S. zeamais, Tribolium castaneum and Trogoderma granarium. Tests were conducted as appropriate at 10, 15, 25 and 30°C, all at 70% r.h., with concentrations ranging from 0.013 to 2.96 mg/l and exposure times from 1 to 16 days. Sitophilus spp. proved the most tolerant, and in all species other than T. granarium, in which diapausing larvae were the more tolerant in longer exposures, eggs and pupae were the most tolerant stages. Phosphine was most effective at the higher temperatures, whilst long exposures at low concentrations were far more effective than short exposures at high concentrations. The use of phosphine to control these species of stored-product insects will only be effective at 15°C or below if long exposures can be guaranteed.     

The effect of temperature and humidity on the developmental period and mortality of Typhaea stercorea (L.) (Coleoptera: Mycetophagidae)

The development of Typhaea stercorea (L.) on kibbled wheat was investigated at temperatures from 15 to 30°C in combination with humidities from 70 to 90% r.h. Eggs hatched at 17.5–30°C but not at 15°C. Incubation periods ranged from 2.5 days at 30°C to 9.5 days at 17.5°C. Larval periods ranged from 9.7 days at 30°C, 90% r.h. to 83.6 days at 17.5°C, 80% r.h. and were more than doubled for each 10% decrease in humidity. At 70% r.h. all larvae died outside the temperature range 22.5–27.5°C. Mortality increased with decreasing humidity in the range tested. Pupal periods ranged from 2.9 days at 30°C, 80% r.h. to 13.8 days at 17.5°C, 90% r.h. At 70% r.h. the lowest temperature for pupal development was 25°C whereas at 90% r.h. it was 17.5°C. The results suggest that this species is essentially a mould feeder and confirm that it requires relatively high humidity to develop.     

温度和烟草粉螟密度对麦蛾茧蜂觅食行为的影响

为明确温度和烟草粉螟密度对麦蛾茧蜂觅食行为的影响,设置15、20、25、30和35℃梯度温度,测定了麦蛾茧蜂在不同密度烟草粉螟5龄幼虫条件下的功能反应、寄生量和产卵量。结果表明,麦蛾茧蜂的麻痹量随温度的升高和烟草粉螟密度的增大而增大,其功能反应为Holling Ⅱ模型;麦蛾茧蜂的瞬时攻击率（a）随温度的升高先增大后降低（25℃最大）,处理时间（Th）随温度的升高而缩短;在30～35℃条件下麦蛾茧蜂对烟草粉螟的控害潜力（a/Th和T/Th）最大。麦蛾茧蜂的寄生量、产卵量和转化率均随温度的升高而增大,随烟草粉螟密度的增大而减小。当温度在30～35℃和烟草粉螟为5～10头/盒时,麦蛾茧蜂的寄生量、产卵量和转化率较高。本研究为大量饲养和利用麦蛾茧蜂防治烟草粉螟等仓储害虫提供了理论依据。     

Effect of constant temperature and humidity on oviposition and development of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) on bambara groundnut, Vigna subterranea (L.) Verdcourt

The effect of different conditions of temperature and humidity on oviposition and development of Callosobruchus maculatus and Callosobruchus subinnotatus was investigated in the present study. Four temperatures (25°C, 30°C, 35°C and 40°C) and three humidities (30%, 60% and 90% r.h.) were evaluated on both species in pure and mixed populations on bambara groundnut (Vigna subterranea) seeds. In both pure and mixed populations, temperature influenced oviposition and progeny development of both species significantly more than humidity. Egg-laying and progeny development in C. maculatus were optimal at 35°C. In contrast, oviposition and progeny development in C. subinnotatus were optimal at 30°C. In mixed populations, where eggs were laid by females of C. maculatus and C. subinnotatus held together, more C. maculatus adults than C. subinnotatus adults were produced at the various temperatures and humidities. No adult progeny of either species developed in pure or mixed populations at 40°C. C. maculatus was more fecund than C. subinnotatus and development from egg to adult took much longer in C. subinnotatus than in C. maculatus in both pure and mixed populations. The implications of these findings for the development and survival of both species in the different agroecologies and seasons in Nigeria are discussed.     

Fungal colonists of maize grain conditioned at constant temperatures and humidities

Fungal colonization of shelled maize (Pioneer 3320) harvested from a field near Furman, South Carolina, in 1992 was determined after 348 and 751 days of continuous storage at each of seven temperatures (10, 15, 20, 25, 30, 35, or 40°C) and four constant relative humidities, giving equilibrium grain moisture contents ranging from 9.4% to 17.5% m.c. in 28 grain conditioning environments. Twenty fungal species infected surface sterilized seeds and were recorded from these conditioned grain treatments, including species commonly found in preharvest maize [e.g. Acremonium zeae, Aspergillus flavus, Fusarium moniliforme (syn. F. verticillioides), Penicillium pinophilum (syn. P. funiculosum), etc.]. Eupenicillium cinnamopurpureum and Monascus ruber were recorded only from conditioned grain treatments. Eurotium chevalieri colonized 50–96% of the kernels from grain conditioning treatments with the highest moisture content for each incubation temperature. Grain samples with>33% E. chevalieri infection had a decreased occurrence of F. moniliforme and A. zeae, and no kernels from these samples germinated. No fungi colonized more than 50% of the kernels conditioned at 30–40°C and 9.4–14.2% m.c. The results of this study indicate that individual patterns of fungal colonization during grain conditioning were a function of the survival rates for preharvest fungal colonists and their potential replacement by E. chevalieri.     

Observations on the susceptibility of compressed dried grass and legume to infestation by some storage insects

Under conditions controlled at 25°C and 70% r.h. and under outdoor conditions in southern England, the storage insect pests Sitophilus granarius (L.), Oryzaephilus surinamensis (L.), Cryptolestes ferrugineus (Steph.) and Ephestia elutella (Hueb.) were unable to breed or to survive for long on blocks of compressed, dried forage (grass or legume). The beetles Ptinus tectus Boield. and Trigonogenius globulus Sol. were able to breed on this material under both sets of conditions, but Stegobium paniceum (L.) only at 25°C. At the higher relative humidities associated with outdoor conditions the moths Hofmannophila pseudospretella (Staint.) and Endrosis sarcitrella L. produced thriving cultures. The damage caused by S. paniceum and the moths was severe; in particular, H. pseudospretella completely destroyed the foodstuff during 1 yr of storage at ambient outdoor shade temperatures in Britain.     

麦蛾茧蜂对烟草粉螟的控制潜能研究

为明确麦蛾茧蜂对烟草粉螟的控制潜能,研究了麦蛾茧蜂对烟草粉螟幼虫的偏好性、功能反应、种内干扰和雄蜂存在对雌蜂的干扰效应。结果表明,麦蛾茧蜂偏好麻痹5龄幼虫,平均麻痹率74.00%±2.67%,对5龄幼虫的功能反应符合Ⅱ型,瞬时攻击率、处理时间、最大麻痹量分别为0.085/h、0.187 h和128.06头;麦蛾茧蜂种内干扰系数为0.316,该蜂对烟草粉螟幼虫的平均麻痹率（0.226~0.566）和搜寻效率（0.476~0.836）均随着雌蜂密度的增加而显著降低,但雄蜂的密度不影响雌蜂对烟草粉螟的麻痹量。研究证明,麦蛾茧蜂对烟草粉螟的控制潜力大,在烟仓烟草粉螟的绿色防控中具有良好的开发利用前景。     

Some laboratory observations on the development of two African strains of Plodia interpunctella (Hübn.) (Lepidoptera: Phycitidae), with particular reference to the incidence of diapause

Laboratory investigations were made on the development of two African strains of Plodia interpunctella on a mixture of wheatfeed, glycerol and dried yeast at four teperatures from 17·5°C to 25°C at 50% r.h. and at 17·5°C and 30°C at 70% r.h. Particular attention was given to the possible incidence of a pre-pupal diapause in the two stains, one from Kano, Nigeria and the other from Pretoria, South Africa.

At 30°C there was little difference between strains, but at 22·5 and 25°C the development period of the larva and possibly also of the pupa was longer in the Pretoria strain. At 20 and 17·5°C this difference was extremely large for larvae and at 17·5°C reached 4 days for pupae. The difference in the time for larval development, e.g. average 164·8 and 206 days in the Pretoria strain, and 38·1 and 57·5 days in the Kano strain, at 20 and 17·5°C (50% r.h.) respectively, was due to a prolonged pre-pupal diapause in the former strain.

It was shown that diapause was induced in the Pretoria strain when eggs were incubated at 25 or 30°C and newly-hatched larvae transferred to 20°C; also when larval development commenced at 30°C and larvae were transferred to 20°C before the end of the second instar.

The incidence of diapause in the Pretoria strain and its absence in the Kano strain is discussed in relation to climatic data and reference is made to the possible implications of diapause in relation to control, with particular reference to fumigation.     

Temperature and water activity effects on growth and temporal deoxynivalenol production by two Argentinean strains of Fusarium graminearum on irradiated wheat grain

The ability of six strains of Pichia anomala, four strains of Pichia kluyveri and two strains of Hanseniaspora uvarum predominant during coffee processing to produce polygalacturonase (PG), pectin esterase (PE) and pectin lyase (PL) in yeast polygalacturonic acid medium (YPA) and in coffee broth (CB) was studied. For comparison, a reference strain of Kluyveromyces marxianus CCT 3172 isolated from cocoa and reported to produce high amount of PG was included.

Initial screening of PG activity using YPA medium showed that K. marxianus CCT 3172, P. anomala S16 and P. kluyveri S13Y4 had the strongest activity. Enzymatic assays showed that the four yeast species secreted PG, but none of the yeasts investigated was found to produce PE or PL. P. anomala S16 and P. kluyveri S13Y4 were found to produce higher amounts of PG when grown in CB than in YPA. When K. marxianus CCT 3172, P. anomala S16 and P. kluyveri S13Y4 were grown in YPA broth adjusted to pH of 3.0–8.0 and incubated at temperatures of 15–40 °C, the three yeast species secreted the highest amount of PG at pH 6.0 and at 30 °C. For PG secreted by K. marxianus CCT 3172 and P. anomala S16, the optimum pH and temperature for the enzymatic activity were 5.5 and 40 °C, respectively. On the other hand, PG produced by P. kluyveri S13Y4 showed the highest activity at pH 5.0 and 50 °C.

Significant differences in the extracellular activity of PG were found between the yeasts species as well as between strains within same species. High amounts of PG were produced by two strains of P. anomala and P. kluyveri. It is therefore likely that strains of those two species may be involved in the degradation of pectin during coffee fermentation.     

Adult longevity and oviposition of Trogoderma parabile Beal (Coleoptera, Dermestidae) at different temperatures

Adult longevity and egg production of Trogoderma parabile Beal were determined at 14 temperatures from 4·4 to 40°C and 70±5 per cent r.h. In the range 12·8 to 32·5°C male and female longevity decreased with increasing temperature, particularly above 17·5°C. At temperatures below 12·8°C longevity decreased rapidly. From 22·5 to 37·5°C females had a shorter life span than males; but at all other temperatures females outlived males. The lengths of the preoviposition and oviposition periods were inversely related to temperature. Eggs of normal appearance were laid at temperatures from 17·5 to 37·5°C, a few deformed, non-viable eggs were laid at 15·6°C, and none beyond this range. Most eggs were laid at temperatures of 27·5 and 30°C. The number of fecund females rose as the temperature increased from 17·5 to 35°C and declined beyond 37·5°C. As the temperature increased above 17·5°C there was generally an inverse relationship between oviposition period and temperature. Females alternately exposed for 24-hr periods at 32·5 and 15·6°C during their adult life produced about the same total number of eggs as those held continuously at 32·5°C. The number of laying females and egg production per female on individual days was directly related to temperature. The finite rate of increase (λ) of T. parabile at 32·2±0·3°C and 70 per cent r.h. was 1·7 per 8 days. The results suggest that in Canada T. parabile is unlikely to become a serious pest of stored grain because of low winter temperatures and relatively short summers in the primary grain-growing regions.     

The suitability of dried fruits, almonds and carobs for the development of Ephestia figulilella Gregson, E. calidella (Guenee) and E. cautella (Walker) (Lepidoptera: Phycitidae)

In experiments at 30°C, 70% r.h. and a light régime of 16 hr light/8 hr dark 30 freshly-hatched larvae were placed singly on ripe carob pods obtained direct from Cyprus, and almonds, dates and raisins bought from a shop. The raisins had been treated commercially with paraffin oil prior to export. All 3 species thrived on ground carobs and dates. Between 17 and 26 individuals of each of these species completed development and emerged as adults on these foods. The particle size of carobs had a considerable influence, for only 13 E. calidella and 8 of each of E. figulilella and E. cautella completed development on carob pieces. Only 1 adult of E. calidella was bred from almonds, and 2 from raisins; 9 adults of E. figulilella were bred from almonds, and 16 from raisins, whilst E. cautella gave 17 adults on almonds and 3 adults on raisins.

The shortest mean developmental period for E. figulilella was 34 days on ground carobs, for E. calidella it was 37 days on carob pieces and for E. cautella 35 days on almonds. The longest mean developmental periods were 56 days for E. figulilella and 59 days for E. calidella, both on almonds, and 84 days for E. cautella on raisins.

The significance of these laboratory results in relation to field and warehouse observations is discussed.     

The susceptibility of the immature and adult stages of Sitophilus granarius to phosphine

A concentration of 4 mg/l. of phosphine applied for 8 hr at 25°C permitted a considerable survival of the developmental stages of Sitophilus granarius (L.). Eggs of 3–4 days old were very tolerant and pupae even more so but larvae were very susceptible. A concentration of 1 mg/l. applied for 32 hr completely killed all stages except pupae. The most tolerant eggs were 2–4 days old. At 0·5 mg/l., pupae were again the most tolerant stage and eggs were most tolerant at 1–2 days old. At 0·3 mg/l. or less the majority of eggs were killed during the fifth day of development irrespective of their age at the start of fumigation, but over half were dead by 4 days old at 0·4 mg/l. and about a third survived beyond the sixth day at 0·05 mg/l. It is only at these latter concentrations at these ages that mortality of eggs was clearly related to dosage.

The physiological age range of pupae in samples was more dispersed. Pupae were most tolerant to phosphine at about 32 days old. From 5 to 7 days were needed for complete mortality at concentrations of 0·1–0·05 mg/l.

Adults were very susceptible to phosphine, all being killed by 8 hr at 1 mg/l. which permitted survival of some larvae. Freshly emerged adults were the most tolerant; older adults were very susceptible, at 1 month old being killed by 4 hr at 1 mg/l. and 3 days at 0·01 mg/l. Insects surviving fumigation as larvae or pupae usually laid fewer eggs than controls though their longevity was unaffected. Those surviving fumigation as eggs were not adversely affected. There is a possibility that some individuals surviving, as eggs or pupae, a fumigation causing very high mortality may lay more rapidly than controls.