Sensitive periods for wing development and precocious metamorphosis after precocene treatment of the brown planthopper,Nilaparvata lugens

The critical periods for juvenile hormone suppression of wing development and metamorphosis were examined in a pure brachypterous line of Nilaparvata lugens following topical application of Precocene II (PII) to various stages of the third and fourth nymphal stadia. When PII, in doses ranging from 10 pg to 100 ng, was applied to 12-h-old third or 6-h-old fourth stadium nymphs, long-wing formation (macroptery) was induced. Macropter induction ranged from 5 to 50% in females and from 30 to 50% in males, the effect being more prominent in males. The sensitive period for macropter induction lasted from the early second stadium through to day one of the fourth (penultimate) stadium. Beyond that period nymphs required sensitivity to PII and the numbers of macropters increased towards the final nymphal molt, again males were more sensitive. On the other hand, periods sensitive to PII for precocious metamorphosis induction appeared from early second stadium to 18 h after molting to the third nymphal stadium. Overlapping application of JH-III with PII at early third stadium could totally inhibit the occurrence of precocious metamorphosis and significantly rescue the macropter induction. From the data described, a scheme is presented for the control of wing development and metamorphosis by juvenile hormone, assuming two types of threshold value determining wing form and metamorphosis.     

Temperature dependent development of Lygus hesperus (Hemiptera: Miridae) nymphs

Lygus hesperus Knight (Hemiptera: Miridae) is a key pest of fruit and vegetable crops, forages, and cotton (Gossypium spp.) in the western United States. Accurate models describing relationships between temperature and L. hesperus development are critical to the study of seasonal L. hesperus population dynamics. Development of L. hesperus nymphs was assessed at nine constant temperatures from 10 to 37.8 degrees C. The relationships between temperature and development for each L. hesperus instar, and for the entire nymphal stage, were best described by six-parameter biophysical models indicating both low- and high-temperature inhibition of development. Development rates asymptotically approached zero with decreasing temperature in the lower thermal range, and decreased with increasing temperatures above 32.2 degrees C. Nymphs did not survive from egg hatch to adulthood at either 10 or 37.8 degrees C, and nymph mortality was > 90% at both 12.8 and 35.0 degrees C. The fifth instar exhibited the longest stadium, whereas the shortest stadia were associated with the second and third instars. Development rates of males and females did not differ, and the ratio of males to females was not different from 1:1 at any temperature. Our temperature-dependent development rate models for L. hesperus nymphs will facilitate control of insect physiological age in controlled laboratory experiments, and should be useful in planning and interpreting field studies on L. hesperus population dynamics.     

Developmental changes in fatty acid biosynthesis and composition in the house cricket,Acheta domesticus

Incorporation of [1-¹⁴C] acetate into various phospholipid and triacylglycerol fatty acids showed cyclic fluctuations in fatty acid biosynthesis that were similar for all of the major fatty acids in both male and female house crickets, Acheta domesticus, during development. All three stadia showed low levels of biosynthesis near ecdysis followed by increased synthesis to a peak at midstadium. In the phospholipid fraction, the incorporation of newly synthesized saturated fatty acids, 16:0 and 18:0, predominated near ecdysis, while at midstadium linoleic acid was the most actively synthesized fatty acid. In the triacylglycerol fraction, 18:0 and 18:1 predominated throughout the entire stadium. In contrast to the large fluctuations in fatty acid biosynthesis, the fatty acid compositions of the phospholipid and triacylglycerol fractions did not change within a stadium. However, significant differences were demonstrated between the stages and were associated primarily with differences between nymphal and adult stadia. Males and females differed in the proportions of 16:0 and 18:2 incorporated into phospholipids with females showing a greater proportion of 18:2 and a corresponding smaller proportion of 16:0 than males. The greater proportion of linoleic acid in females and in adults in general compared to nymphs and the predominance of the incorporation of newly synthesized linoleic acid into the phospholipid fraction of all stadia are consistent with the importance of this fatty acid in a number of biological roles.     

Electroantennogram responses of aphid nymphs to plant volatiles

Abstract. Electroantennogram (EAG) responses of immature aphids were investigated for 30 plant volatile compounds in third‐ and fourth‐stadium nymphs of the black bean aphid, Aphis fabae. The nymphs were destined to develop into adult alate (winged) virginoparae. The EAG response profiles were similar to those previously reported in the adults. Among the compounds tested, hexanonitrile elicited the largest EAG responses in both nymphal stadia, corresponding to previously reported results with adults. Six‐carbon aliphatic compounds showed relatively higher EAG activities in the nymphs but, in contrast, (E)‐2‐hexenal, benzaldehyde, α‐pinene and β‐pinene, and citronellal elicited relatively smaller EAG responses in nymphs than adults. Although overall EAG response profiles were similar between the third and the fourth stadia for the majority of the volatiles, four aldehyde compounds, hexanal (E)‐2‐heptenal, 2‐hydroxybenzaldehyde and citronellal, showed relatively higher EAG activities in the third than in the fourth stadium. The present study indicates that aphid nymphs possess a functional olfactory receptor system before the antennae are fully developed morphologically and physiologically.     

Influence of social situation on food consumption and growth in nymphs of the house cricket, Acheta domesticus

ABSTRACT. Grouped nymphs of Acheta domesticus L. (Orth., Gryllidae), which mature faster than isolated ones (Chauvin, 1958), consumed more food per milligram of body weight and converted it to body tissue more efficiently than did isolated nymphs, during the fifth and sixth instars. Grouped nymphs; usually had fewer instars than isolated ones. Feeding and growth rates did not decline after isolation part-way through development. Previously isolated females, paired at 25 days, matured as rapidly as females paired throughout development, but isolated males paired at 25 days matured no faster than males which remained isolated. Nymphs paired with an older cricket gained weight as fast as nymphs in same-age pairs in early instars, but their rate of weight gain declined in later instars, and their maturation was slower. However, all females, and males paired with older males, were heavier at emergence as adults than were adults from same-age pairs. When grouped with both an older cricket and one of the same age, females developed at normal rates, but males still showed some retardation.     

An adaptive benefit of facultative coprophagy in the German cockroach Blattella germanica

1. A possible adaptive benefit of coprophagy was investigated in nymphs of the German cockroach Blattella germanica (L.). 2. Newly ecdysed first instars, given no source of food other than conspecific faeces, survived significantly longer than first instars deprived of faeces. The faeces of adult males and females may be of different quality, however, because nymphs given female faeces were more likely to moult into the second stadium than nymphs given male faeces. 3. In contrast to first instars, second instars provided adult faeces survived only slightly longer than starved counterparts. Faecal feeding is therefore stage‐specific, as is the benefit derived from it. 4. The relationship between the nutrient composition of faeces and the survival of nymphs was also examined. First instars fed the faeces of adults that had been maintained on a high (50%) protein diet, died more slowly than first instars fed the faeces of adults that had been maintained on medium (22.5%) and low (5%) protein diets. Chemical analysis of faeces showed that the concentration of protein in adult faeces increased with the level of protein in the diet. Moreover, food choice assays showed that first instars, unlike adults, ingested more of the high‐protein diets. 5. These data support the idea that coprophagy is a stage‐specific adaptive behaviour that permits first instars to moult into the second stadium with minimal foraging.     

Effects of a juvenile hormone analog, pyriproxyfen, on the apterous form of Lipaphis erysimi

Effects of a juvenile hormone analog, pyriproxyfen, on various developmental stadia of the apterous form of the turnip aphid, Lipaphis erysimi (Kaltenbach), were bioassayed at three concentrations (50, 100, and 150 mg [AI]/l) in the laboratory. Supernumerary-molted nymphs with 1-3 extra molts were found when the first three nymphal instars were treated, and all these nymphs died prematurely. In contrast, all treated fourth instar nymphs molted normally to adults. The longevity of all pyriproxyfen-treated L. erysimi nymphs and adults and the fecundity of treated adults were reduced by 50%. Higher concentrations of pyriproxyfen (100 and 150 mg [AI]/l) caused sterility in adults from treated fourth instars; whereas the lowest concentration (50 mg [AI]/l) did not cause any adult sterility. A majority of adults from treated fourth instars and treated adults produced normal nymphs, and some adults produced dead nymphs with normal appendages or dead and deformed nymphs without any appendages. Normal nymphs produced by the adults from treated adults or treated at fourth instars developed more slowly from first instar to adult than the water-treated nymphs, and all adults in the new generation apparently reproduced normally. The potential role of pyriproxyfen in a vegetable aphid IPM program was discussed.     

1-Phenyl-2-pentanone and methyl salicylate: new defense allomone components and their content shift during ontogenetic development of the millipede <Emphasis Type="Italic">Nedyopus tambanus mangaesinus</Emphasis> (Polydesmida: Paradoxosomatidae)

Twelve components were identified in hexane extracts of the polydesmid millipede Nedyopus tambanus mangaesinus (Attems, 1909) and their contents were examined at all stadia of ontogenetic development including two adult conditions (before and after hibernation). Two compounds, 1-phenyl-2-pentanone and methyl salicylate, were newly identified as components of the millipede together with six well-known polydesmoid compounds (benzaldehyde, benzyl alcohol, benzoic acid, benzoyl cyanide, mandelonitrile, and mandelonitrile benzoate) and four phenols (phenol, p-cresol, 2-methoxyphenol, and 2-methoxy-4-methylphenol). Benzaldehyde and benzoyl cyanide were distributed from nymphs at stadium I, and other components started to become detectable at more advanced stadia. The largest content (35.1%) of methyl salicylate was detected in nymphs at stadium I, together with benzaldehyde and benzoyl cyanide, implying the reinforcement of defensive functions during or after egg emergence. The content (18.8%) of 1-phenyl-2-pentanone reached a maximum in hibernated females among all stadia and conditions. Its female-biased distribution at the mating season (ca. 5.7-fold more than in males) implies its sexually related functions.     

The life history and post-embryonic development of "Spirobolus" bivirgatus (Diplopoda: Spirobolida) on Aldabra, Western Indian Ocean

Spirobolus bivirgatus, recently known as Mystalides bivirgatus, passes through 15 stadia. These were differentiated by the ocular field method. Development is anamorphic from stadia I to VIII and epimorphic from stadia IX to XV. Maturity is reached in a few males in the eighth stadium but more normally it occurs in the ninth to twelfth stadium. Females are mature in the ninth to fifteenth stadium. Adult males possess fully developed gonopods as well as soft pads on the ventral surface of the tarsi. The pads are illustrated with scanning electron micrographs. Males die after breeding but females probably breed in three or more successive years. Eggs are laid during the wet season, December to April, and these reach maturity within the second or, possibly, the first year of growth. The density, distribution and food of S. bivirgatus is briefly described.     

Biometric studies of some stoneflies and a mayfly (Plecoptera and Ephemeroptera)

Aspects of the nymphal/adult developmental change were investigated in biometric studies of several species of Plecoptera: Nemouridae near Schlitz, Hesse, Germany. Preliminary information on the mayfly, Baetis vernus Curtis, is also provided. Nemourid nymphs pass through 3 wing bearing stages before reaching adulthood. Instars can be identified by their characteristic shapes, as expressed by the wing length/head width (WL/HW) ratio. Size does not allow instar discrimination, mainly due to sexual size differences. HW is ca 10% larger in last instar female than in male nemourid nymphs; exuviae shed at the moult to adult represent about 14% of nymphal ash free dry weight (AFDW). Biomass lost with exuviae during the many larval moults should be accounted for in estimates of production. Freshly emerged nemourid females are about 6% larger and 30% heavier than males. The HW/AFDW relationship is the same in both sexes. Through terrestrial feeding during adult life, males double their weight on average. Mature females are up to three times heavier than freshly emerged ones. They invest about 30% of their final AFDW in reproduction.Shape of last instar nymphal Baetis was expressed as the ratio wing length/mesonotum length. It is size-dependent, a characteristic, instar-specific shape may not occur in this mayfly. Nymphal and subimaginal exuviae together represent about 14% of last instar nymphal dry weight. Females of Baetis are about 55% heavier than males. Unlike in Plecoptera, the size/weight (ML/AFDW) relationship differs between sexes.     

Fecundity,nymphal development and longevity of field‐collected tropical bedbugs,Cimex hemipterus

This study examined the fecundity, oviposition, nymphal development and longevity of field‐collected samples of the tropical bedbug, Cimex hemipterus (Fabricius) (Hemiptera: Cimicidae). Under environmental conditions of 26±2°C, 70 ± 5% relative humidity and a 12‐h photoperiod, with bloodmeals provided by a human host, six strains of tropical bedbug had a fecundity of up to 50 eggs per lifetime, over 11–14 oviposition cycles. Increased feeding frequency improved fecundity. After feeding and mating, adult females normally took 2–3 days to produce a first batch of eggs. The oviposition period lasted 2–7 days before cessation of the oviposition cycle. The egg incubation period usually lasted 5–7 days before the emergence of first instars. The nymphs underwent five stadia (the first four of which each took 3–4 days, whereas the last took 4–5 days) before becoming adults at a sex ratio of 1 : 1. More than five bloodmeals were required by the nymphs to ensure a successful moult. Unmated adults lived significantly longer than mated adults (P < 0.05). Unmated females lived up to almost 7 months, but the longevity of mated males and females did not differ significantly (P > 0.05).     

Maternal death relaxes developmental inhibition in nymphal aphid defenders

In certain aphids, first-instar nymphs defend their gall by attacking intruding arthropod predators. One correlate of such defensive behaviour is a lengthened duration of the first nymphal stadium during the galling phase of the life cycle. A prolonged first stadium allows a large army of first-instar defenders to accumulate, which may be advantageous for gall defence. The factors determining developmental delay have been unclear, however. Our field experiment with Pemphigus obesinymphae, a North American gall-forming aphid with defensive first-instar nymphs, tests whether first-stadium duration is influenced by the death of the colony''s fundatrix (mother). We killed fundatrices in certain galls, left those in control galls alive, and counted aphids in each stadium in each gall. Galls in which fundatrices were killed contained a lower proportion of first-instar defenders and more late-instar nymphs than did galls with living fundatrices, indicating that maternal death dramatically increased developmental rate of nymphs. Possibly nymphal aphids respond adaptively to environmental cues that signal a threat to the colony''s welfare. Alternatively, the fundatrix actively suppresses offspring development in order to maintain a large army of soldiers to protect her gall. The results add a new layer of complexity to our understanding of social aphid systems.     

Notes on the life-history and ecology of Tachypodoiulus niger (Diplopoda, Iulidae) in Britain

In some iulids females can moult several times after first attaining maturity but males cannot. Males of Tachypodoiulus niger (Leach) are exceptional in that they can moult, but they lose their functional intromittent organs in the process, regaining them after a second moult. The process can be repeated, a series of functional males alternating with nonfunctional males. This extension of the life and the consequent increase in number of segments led Verhoeff (1928) to postulate that the ancestral millipede was short-bodied and that many-segmented forms were derived from it. We think that this extension of life is of ecological rather than phylogenetic significance–adapting the species to disperse widely to scattered habitats. In particular, the extension of life of males as well as of females may ensure a reasonable sex ratio in those areas where the species is least dense.
In Britain, Tachypodoiulus niger lays eggs in spring which reach the fourth and fifth stadia by their first winter and the seventh, eighth and ninth stadia by their second winter. Maturity is usually attained by males in the eighth stadium but occasional specimens mature at stadium seven and others defer maturity until the ninth. Both sexes can proceed to the fourteenth stadium but adults in Britain usually belong to two generations of two and three years old, divided mainly between the eighth, ninth and tenth stadia. Details are given of a large collection made by the late Dr Scott of animals taking refuge in his house at Henley-on-Thames. Animals in Britain appear to have a similar life history to those in Germany as described by Verhoeff, but effective comparison has depended on correcting and re-interpreting some of Verhoeff's data.     

Changes in desiccation resistance during development in the millipede Polydesmus angustus

Water loss at increasing temperature in dry air (< 5% r.h.) was measured for the eight stadia of Polydesmus angustus Latzel (Diplopoda, Polydesmida: Polydesmidae). Instantaneous rates of water loss, expressed as percentages of original body water, were calculated at 20, 25 and 30°C. At each temperature, the rate of water loss varied greatly among stadia, decreasing between 15‐ and 18‐fold from stadium I to stadium VII, and then significantly increasing from stadium VII to stadium VIII (adult). In all stadia, the rate of water loss increased with rising temperature, but the temperature effect was much more pronounced in juveniles than in larger stadia. The threshold temperature of heat stupor, which was measured from stadium IV onwards, increased significantly during development, from 35.6°C in stadium IV to 39.5°C in adults. Survival at 20°C and 76% r.h. varied as could be expected from the water loss rates in dry air, survival time increasing from stadium I to stadium VII and then decreasing from stadium VII to the adult stage. The maximum tolerable water loss, estimated for stadia V, VII and adults, did not change significantly among stadia (mean: 47% of the original water content), suggesting that survival times under desiccating conditions depended primarily on the rates of water loss. The relevance of the results in terms of summer survival under natural conditions is discussed, and it is concluded that juvenile mortality could be substantial in the field. This is important for understanding the adaptive value of cohort‐splitting in P. angustus.     

高温对稻褐飞虱发育与生殖的影响

通过高温处理及交配产卵实验,探讨了高温对稻褐飞虱Nilaparvata lugens (Stal)发育与生殖的影响。研究了不同高温条件对褐飞虱若虫发育历期、产卵量、产卵前期、寿命等生物学特性的影响。34℃以上高温导致褐飞虱若虫发育历期延长。高温处理4龄若虫使羽化后的雌成虫产卵量减少。高温处理不同日龄雌成虫也致使其产卵量减少,其中以1日龄短翅型、3日龄长翅型的产卵量影响最大。高温处理后褐飞虱寿命缩短。高温恒温处理,对短翅型雌成虫的产卵前期影响不大,但能延长长翅型雌成虫的产卵前期;而高温变温处理致使短、长翅型雌成虫的产卵前期均延长。高温变温对褐飞虱生殖的影响程度大于高温恒温。高温处理组雌、雄成虫与对照组相应的成虫交配试验表明,高温对雌性的影响大于雄性。实验初步确定34℃为对褐飞虱发育与生殖产生影响的临界温度。     

Additional moults into 'elongatus' males in laboratory-reared Polydesmus angustus Latzel, 1884 (Diplopoda, Polydesmida, Polydesmidae) - implications for taxonomy

The number of stadia during post-embryonic development is supposed to be fixed in most species of the millipede order Polydesmida. For the first time since 1928, additional moults were observed in two males of Polydesmus angustus Latzel, 1884 reared in the laboratory. These 'elongatus' males sensu Verhoeff reached stadium IX instead of stadium VIII, with addition of a further podous ring (32 pairs of legs). One male had well-developed gonopods at stadium VIII, which regressed at stadium IX; the other had no gonopods at stadium VIII, which developed at stadium IX. The two cases correspond to the 'regressionis' and 'progressionis' forms described by Verhoeff in Polydesmus complanatus (Linnaeus, 1761), which confirms entirely his results. Additional moults appear to be associated with small body sizes and possible underlying mechanisms are discussed. Comparisons between millipede orders indicate that post-embryonic development is less strictly canalized in Polydesmida than in Chordeumatida. This implies that the adult number of body rings is of limited taxonomic value in Polydesmida and should not be viewed as a character of generic importance.     

Changes in salivary nitrophorin profile during the life cycle of the blood-sucking bug Rhodnius prolixus

The insect Rhodnius prolixus is a hematophagous hemipteran that has five nymphal instars. Fifth instar nymphs contain, in their salivary glands, four nitrophorins which have already been described in the literature (NP1, NP2, NP3 and NP4). Two new hemeproteins were isolated and partially characterized from first instar nymphs. NP2, that shows an anticoagulant activity, was also identified, but NP1, NP3 and NP4 were not found. As these new hemeproteins have amino-terminal sequences clearly homologous to already described nitrophorins and were capable of binding nitric oxide, they were named nitrophorins 5 and 6, although they showed an unusual Soret band at 412 nm. In each subsequent nymphal stage, a new nitrophorin emerges. In the second instar, NP4 comes into view, in the third instar NP1 appears, and NP3 is only found in fifth instar nymphs and adults, showing that the nitrophorin profile of R. prolixus saliva is stage-specific.     

The manifestation of sexual dimorphism in the preimago phases of 2 species of the genus Hyalomma (Ixodoidea, Ixodidae)

Experiments on laboratory cultures of Hyalomma asiaticum and H. anatolicum have shown that at the nymphal phase sexual dimorphism manifests itself in statistically reliable differences between general sizes and mass of the body of male and female individuals. Larger nymphs moult mostly into females, small ones mostly into males. Reliable differences have been noted in the sizes of scutum, gnathosoma and its appendages in male and female nymphs of both species. At the larval phase sexual dimorphism does not manifest itself in the sizes of individuals.     

Effects of fenoxycarb on development and reproduction of the Oriental cockroach, Blatta orientalis

Abstract. In a laboratory study, groups of third-instar Blatta orientalis nymphs were reared to adulthood in arenas containing fenoxycarb (48 mg a.i./m²) treated ceramic or plywood tiles. The reproductive capacity of the emergent adults was assessed by pairing each individual with two untreated individuals of the opposite sex. Oothecal production, oothecal hatch and the numbers of nymphs emergent from each hatched ootheca were monitored. Exposure to 1-day-old deposits of fenoxycarb reduced adult emergence by 45–75% in comparison with an untreated control treatment. Substantial (>40%) mortality also resulted when nymphs were exposed to deposits up to 3 months old on plywood and up to 6 months old on ceramic. Exposure to fenoxycarb significantly extended the time taken to reach adulthood of males contacting 6-month-old deposits on both surfaces, and of females contacting 1-year-old deposits on ceramic. Adult females exposed as nymphs to fenoxycarb were unable to produce oothecae, except one female laid a non-viable ootheca. Untreated females paired with treated males produced large numbers of oothecae of normal appearance but very low viability, with only 0–7.1% hatching. With marked effects on both development and reproduction in B. orientalis , fenoxycarb is a promising agent for control of this species.     

Ontogenetic changes in immunity and susceptibility to fungal infection in Mormon crickets Anabrus simplex

Insects have innate immunity that may be weakened by resource allocation to growth. I measured enzymatic immunity, encapsulation response, and susceptibility to fungal infection in Mormon crickets of known age. Although the concentrations of circulating spontaneous and total phenoloxidase (PO) increased with age from the most recent molt in late instar nymphs (5th, 6th, and 7th) and 0-5 day old adults, mean values did not differ between stadia, indicating that circulating PO titers are knocked back with each molt. In contrast, encapsulation rate increased throughout nymphal development and adult maturation. No longer required to molt, adult PO titers increased steadily with age. Survivorship also increased with the age at which Metarhizium acridum fungus was applied to adults. I conclude that immunity relevant to defense against fungi continues to develop well into the adult stage. With each molt setting the insects back in circulating PO titers, very young adults are much like nymphs in enzymatic immunity.