Effect of nitrogen on resistance of sweet potato to sweetpotato weevil (Coleoptera: Curculionidae) and on storage root chemistry.

The effects of nitrogen fertilizer on sweet potato, Ipomoea batatas (L.) Poir., resistance to the sweetpotato weevil, Cylas formicarius elegantulus (Summers), was studied. Adult weevil feeding and oviposition preference, larval survival, and pupal weight were used as measures of sweet potato resistance. Sweet potato resin glycosides and caffeic acid concentrations in the periderm tissue of storage roots also were measured. Sweet potato genotypes (Beauregard, Excel, W-244, W-250, and Sumor) with varying levels of resistance to sweetpotato weevil were grown in the field under three nitrogen regimes (0, 45, and 135 kg N/ha). Harvested storage roots were evaluated in the laboratory for feeding and oviposition activity of sweetpotato weevil female adults under no-choice and choice test conditions. Larval survival rate and pupal weight were determined by rearing the insects individually on storage root sections. Nitrogen level had a significant effect on the number of eggs deposited, but not on the number of feeding punctures. Sweetpotato weevils laid fewer eggs on plants with the highest level of nitrogen. Nitrogen levels did not significantly affect larval survival and pupal weight. Genotype had a significant effect on feeding, oviposition, and larval survival. Beauregard had higher levels of feeding, oviposition, and larval survival compared with the other genotypes. No interaction effects between nitrogen and genotype were significant. Resin glycosides and caffeic acid concentrations were significantly different among genotypes and between years. Nitrogen levels significantly affected the concentrations of caffeic acid in 1997.     

Contagious egg-distribution on host pods and avoidance of pods received eggs in a wild bruchidKytorhinus sharpianus

The present study investigated the way a wild bruchid, Kytorhinus sharpianus, distributes its eggs on host pods. First, we counted the number of eggs per pod on the host plant (Sophola flavescens) in the field. The egg-distributions by the overwintered-generation adults in July and by the second-generation adults in mid October did not deviate from Poisson distribution because of small numbers of eggs laid. However, the egg-distribution in late August when many first-generation adults emerged was significantly contagious. The deposition of eggs was determined for three types of pods: (A) clean pods, (B) pods with eggs, and (C) those which eggs had been laid on but were removed from later. The numbers of eggs laid newly on three types of pods were significantly different; A>C>B, suggesting that an oviposition marker pheromone (O.M.P.) caused females to avoid pods on which eggs were deposited. Egg-shells reinforced that response. Monte Carlo simulations for the egg-distribution on pods predicted that even if females avoid pods with heavy egg-load through O.M.P., the egg-distribution becomes contagious when there is a large heterogeneity in quality of the pods.     

Identification of the gland secreting oviposition-deterring pheromone in the cabbage seed weevil,Ceutorhynchus assimilis,and the mechanism of pheromone deposition

After laying an egg into a pod of Brassica napus, the female cabbage seed weevil, Ceutorhynchus assimilis, brushes the caudal setae of the eighth abdominal tergite (VIII UT) on the host pod as she walks along it, depositing oviposition-deterring pheromone (ODP). The VIII UT is periodically extended and withdrawn, thus repeatedly rubbing against the posterior fold of the seventh urotergite (VII UT) which bears the individual outlets of glandular epidermal cells. In post-diapause, sexually mature, gravid (i.e. oviferous) females (virgin or mated) the cells of this VII UT gland were hypertrophic, showing intense secretory activity. Extracts of VII UT from these individuals elicited strong electrophysiological responses from antennal club gustatory sensilla and deterred oviposition. In pre-diapause (sexually immature) females, the cells of the VII UT gland were neither hypertrophic nor active and an extract of their VII UT elicited no significant electrophysiological or behavioural response. Extract of female rectum was a less potent oviposition deterrent than VII UT extract and elicited an electrophysiological response similar to male rectum extract. An extract of ovarian calyces and ovaries elicited no behavioural response. We conclude that ODP is secreted by the epidermal cells of the VII UT posterior fold.     

The effect of an oviposition deterring pheromone on egglaying in Pieris brassicae

A laboratory study was conducted in order to determine the influence of the oviposition deterring pheromone (ODP) upon the distribution of eggbatches and eggs by Pieris brassicae females. This pheromone is known to be associated with eggs. Butterflies were offered a choice between cabbage leaves treated in various ways with the ODP and control leaves. The presence of intact conspecific eggs on the treated leaf appeared to have a moderate deterrent effect upon oviposition. An aqueous solution of the ODP, obtained by washing eggs in distilled water was found to have a somewhat higher deterrent effect. Most effective in deterrence of oviposition, however, appeared to be a washing of P. brassicae eggs in methanol. Such a methanol solution can be stored at low temperatures for at least three years without loosing activity. Application of eggwash to either the upper or lower surface of the leaf does not make any difference to females. Percentage deterrence was found to increase with the concentration of eggwash. At very low concentrations no significant difference could be observed anymore in the numbers of eggbatches and eggs laid on control and treated leaf. On the other hand, even very high concentrations of methanol eggwash do not fully protect cabbage leaves against oviposition. Washing P. brassicae eggs seven times consecutively in methanol, a series of pheromone solutions is obtained, all of them were found to possess a high deterrent activity. Although percentage deterrence slowly decreases in subsequent washings, the seventh eggwash sprayed onto cabbage leaves still resulted in less than one quarter of the total number of eggbatches and eggs being laid on the treated leaf.

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Résumé Des expériences de laboratoire ont été réalisées pour déterminer d'influence d'une phéromone dissuasive de la ponte (ODP) sur la distribution des ooplaques et des oeufs de Pieris brassicae. Cette phéromone est connue comme associée aux oeufs. Les papillons ont eu le choix entre des feuilles de chou traitées de différentes façons avec ODP et des feuilles témoins. La présence d'oeufs intacts de la même espèce sur les feuilles a un effet dissuasif modéré sur la ponte. Une solution aqueuse d'ODP, obtenue par lavage des oeufs à l'eau distillée est quelque peu dissuasive. Le lavage des oeufs de P. brassicae au méthanol est apparu comme le plus dissuasif. Une telle solution au méthanol peut être stockée à basse température au moins 3 ans sans perte de son pouvoir. Les applications de l'eau de rinçage sur les faces supérieures ou inférieures des feuilles induisent le même comportement des femelles. L'effet dissuasif augmente avec la concentration de l'eau de rinçage; aux très faibles concentrations, aucune différence significative n'a pu être observée avec les témoins quant au nombre d'ooplaques et d'oeufs. Par ailleurs, même aux très hautes concentrations du méthanol, l'eau de rinçage n'inhibe pas totalement la ponte sur les feuilles de chou. En lavant 7 fois consécutives les oeufs de P. brassicae dans le méthanol, on obtient une série de solutions de phéromones, dont chacune possède un fort pouvoir dissuasif. Bien que l'effet dissuasif diminue lentement avec des rinçages successifs, la pulvérisation du septième rinçage sur les feuilles de chou réduit encore à moins du quart le nombre total d'ooplaques et des oeufs pondus sur la feuille traitée.

     

Physical and chemical plant characters inhibiting the searching behaviour of shape Trichogramma chilonis

Several plant characters are known to affect the searching behaviour and parasitization efficiency of Trichogramma spp. (Hymenoptera: Trichogrammatidae). In this study, plant characters contributing to the low Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) egg parasitism levels on pigeonpea (Cajanus cajan (L.) Millspaugh) were investigated. The efficiency of T. chilonis on pigeonpea was dependent on the plant structure on which the host eggs were found. In a cage experiment, more than 55% of eggs placed on leaves were parasitized, while 1% of eggs on calyxes and no eggs on pods were parasitized. In a filter paper bioassay, parasitoids were deterred by acetone and hexane surface extracts from pigeonpea pods but showed no response to water extract. The searching behaviour of the parasitoids was not affected by different solvent extracts from the surface of pigeonpea leaves. In a four-armed airflow olfactometer, T. chilonis was repelled by volatiles from pigeonpea pods but showed no response to volatiles derived from hexane extract of pod surfaces. Volatile infochemicals and hexane surface extracts from pods of two wild Cajanus species, C. scarabaeoides (L.) Thours and C. platycarpus (Bentham) van der Maesen, were similarly deterrent to T. chilonis. The movement of the parasitoids on pigeonpea pods and calyxes was inhibited by long trichomes and wasps were trapped by sticky trichome exudates. Parasitoids walked significantly faster on leaves than on pods. The walking speed on both pods and leaves increased significantly after washing with hexane. The results presented in this paper show that the plant growth stage and the plant structures preferred by H. armigera for oviposition are the least suitable for T. chilonis, contributing to the low parasitoid efficiency on pigeonpea.     

Factors affecting egg maturation in the bean weevil Callosobruchus maculatus

Abstract. This paper concerns the effects of mate and seed availability on the rate of egg maturation in the bean weevil Callosobruchus maculatus (F.). Egg maturation starts before emergence from the seed and, provided that both oviposition sites and mates are available, eggs are laid at a rate determined by the number of oviposition sites, and mature at a similar rate. If seeds or mates are absent then a small number of eggs are laid, but oocytes continue to mature until the oviduct-capacity is approached. The number of eggs that a female can store is dependent on her body weight and does not correlate with the number of ovarioles. If, after a period in which oocyte development has been halted, conditions for egg-laying become suitable, then egg maturation can be re-started, but only after the oviducts have been emptied of eggs. The rate of egg maturation is then similar to that for females of the same age which have been maturing eggs since emergence.     

Circadian rhythms of feeding, oviposition, and emergence of the boll weevil （Coleoptera： Curculionidae）

Circadian rhythm of feeding, oviposition, and emergence of boll weevil adults were determined at five different photophases （24, 14, 12, 10, and 0 hours） and a constant 27℃ temperature, 65% RH in the laboratory. Squares from Petri dishes, where they were exposed to boll weevil females, were removed and examined for feeding and oviposition punctures every 4 hours during daylight （0700-1900 h） and every 12 h at night （1900-0700 h） over eight consecutive days. Cohorts of randomly selected egg-punctured squares were sampled from ovipositing females at 0700, 1100, 1500, and 1900 during 24 hours and under different photophase treatments, and maintained in Petri dishes at 27 ＋ I℃, 65% RH. Dishes were observed twice daily （1900 and 0700 h） for adults emerging at day or night. Circadian rhythm of oviposition was not affected by the length of the photophase. The boll weevil has round-the-clock circadian rhythm of oviposition, with a daytime preference. We observed that 82.4%-86.0% of the boll weevil eggs were deposited between 0700 and 1900 h, and 14.0%-17.6% between 1900 and 0700 h during a 24-h period. Feeding of boll weevil females in photoperiods 24：0 h （complete light） and 0：24 h （complete darkness） did not significantly change between 0700-1900 h versus 1900-0700 h, while the d .ally cycle of light and darkness in other photoperiods significantly increased the feeding punctures from 0700-1900 compared with 1900-0700 h. The circadian rhythm of emergence depended significantly on the time of oviposition and the length of the photophase. Investigation of boll weevil circadian rhythm provides a better understanding of boll weevil ecology and reveals potential weak links for improving control technologies targeting their reproductive strategies.     

Evidence for an oviposition-deterring pheromone in Tephritis bardanae (Schrank) (Diptera: Tephritidae)

Summary Female Tephritis bardanae (Schrank) exhibit a characteristic ovipositor-dragging behaviour immediately after laying eggs into a flowerbud of Arctium minus (Hill) Bernh. To establish whether this behaviour is associated with an oviposition-deterring pheromone (ODP), female T. bardanae were presented with clean, unattacked flowerbuds and fly activity was monitored using video recording equipment. The distribution of oviposition and fly behaviour were analysed. Avoidance of attacked buds was revealed by the oviposition pattern becoming overdispersed. Spacing out of eggs continued until, on average, each bud contained one egg-batch, after which the distribution became more random or clumped. Analysis of fly behaviour showed that attacked and unattacked buds received similar numbers of visits, but fewer oviposition attempts were made on attacked buds. This behaviour was consistent with use of a contact pheromone deterring repeated oviposition and applied to the bud surface during ovipositor-dragging. Avoidance of attacked buds should increase the efficiency of resource use by T. bardanae populations in the field; however, distributions of egg-batches in flowerhead samples collected from Monks Wood NNR, Cambridgeshire, during 1983–1985, were highly clumped and did not provide supportive evidence. This suggests that the effectiveness of oviposition deterrence in the field is reduced, because the active life of ODP under natural conditions is short, and/or because wild females frequently experience high oviposition drive due to scarcity of suitable flowerbuds.     

Ecophysiological aspects of bruchid reproduction. I. The influence of pod maturity and seeds of Phaseolus vulgaris and the influence of insemination on the reproductive activity ofZabrotes subfasciatus

ABSTRACT.

• 1 Economically important bruchid beetles like Zabrotes sub-fasciatus (Boh.) are able to reproduce both in the field before the legume crop harvest – whilst the seeds are still enclosed within pods – and on seeds in storage sites.
• 2 To take into account this reproductive feature, the influence of pods at different stages of maturity and seeds of Phaseolus vulgaris (Lin.) together with the influence of insemination on the reproductive activity of Zabrotes subfasciatus were examined.
• 3 Female fecundity, insemination and ovarian production were studied under laboratory conditions approximating as closely as possible to the thermal and photoperiodic regimes of the Costa Rican region from which the experimental strain originated.
• 4 The three stages of pod maturity used in experiments (fresh green, fresh yellow and dry yellow pods, all non-dehiscent) induced copulations and significantly stimulated oogenesis. Fecundities of females in the presence of pods were low and did not differ from controls.
• 5 The influence of bean seeds on female reproductive activity was more pronounced than that of pods. Contact with seeds led to a marked increase in the number of sexual meetings, ovarian production and egg-laying activity. Under these conditions, eggs are laid directly on the larvae's food.
• 6 Insemination alone stimulated oogenesis but did not induce egg-laying.
• 7 Possible additive or synergistic interactions between host plant information perceived by females, the effects of egg-laying and insemination are suggested to explain the observed results.
• 8 The adaptive value of this form of reproductive regulation by host plant seeds and pods is discussed in terms of the natural history and oviposition behaviour of Zabrotes subfasciatus.

     

Assessment of patch quality by ladybirds: role of larval tracks

Gravid females of the two-spot ladybird, Adalia bipunctata (L.), were deterred from ovipositing when kept in petri dishes that had previously contained conspecific larvae but not conspecific adults, or the larvae of another two species of ladybird, Adalia decempunctata (L.) and Coccinella septempunctata L. The deterrent effect was density dependent and mediated via a chloroform-soluble contact pheromone present in the larval tracks. Similarly, gravid females of C. septempunctata were deterred from ovipositing by conspecific larval tracks and chloroform extracts of these tracks, but not by the tracks or extracts of tracks of A. bipunctata larvae. That is, in ladybirds the larvae produce a species-specific oviposition-deterring pheromone. In the field, the incidence of egg cannibalism in ladybirds increases very rapidly with the density of conspecific eggs or larvae per unit area. Thus, in responding to the species specific oviposition deterring pheromone female ladybirds reduce the risk of their eggs being eaten and spread their offspring more equally between patches. Received: 14 March 1997 / Accepted: 26 August 1997     

Host-marking pheromone and use of previously established oviposition sites by the mediterranean fruit fly (Diptera: Tephritidae)

Under controlled conditions, the Mediterranean fruit fly, Ceratitis capitata(Wiedemann) preferred to initiate oviposition into preexisting, naturally formed oviposition punctures in a host fruit, kumquat (Fortunella japonica),over establishing new sites on the fruit. This preference was expressed despite the presence of naturally deposited host-marking pheromone (HMP)shown previously to deter oviposition. An almost-identical preference for existing punctures was expressed when females were presented with fruit bearing artificially made punctures on which HMP had been naturally deposited. Using artificial punctures and HMP extracts, the occurrence of punctures was manipulated independently of the presence of HMP.Under field-cage conditions, we found that (1) punctures stimulated egg-laying on kumquats, regardless of HMP treatment; (2) HMP extract inhibited egg-laying, regardless of the occurrence of punctures; and (3) the extent to which HMP inhibited egg-laying was greater on fruit free of punctures than on fruit bearing them. The physiological, evolutionary, and pest management implications of these results are discussed.     

Oviposition deterrents for the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae) from fly faeces extracts

After oviposition, females of the Mediterranean fruit fly Ceratitis capitata Wiedemann deposit a host-marking pheromone on the fruit surface that deters oviposition by conspecifics. Methanolic extracts of fruit fly faeces elicit a similar deterrent effect. The results of laboratory and field experiments using raw methanolic extracts of C. capitata faeces as an oviposition deterrent are reported. Laboratory bioassays revealed a significant positive relationship between concentration of faeces and the inhibition of oviposition responses by C. capitata. Treatment of halves of coffee bushes with methanolic extracts containing 0.1, 1.0 and 10 mg faeces ml(-1) resulted in a significant reduction of infestation only at the highest concentration (P=0.03). Treatment of blocks of coffee bushes with an extract of 10 mg faeces ml(-1) resulted in an 84% reduction in infestation by C. capitata in sprayed plants and a 56% reduction in adjacent untreated coffee bushes surrounding treated plots, probably due to the deterrent effect of host-marking pheromone on fly oviposition. We conclude that faeces contain oviposition deterrent substances that effectively reduce fruit infestations by C. capitata, suggesting a clear potential for the use of this infochemical in integrated management programmes targeted at this pest.     

Reproductive potential of field-collected overwintering boll weevils (Coleoptera: Curculionidae) fed on pollen in the laboratory

Abstract  The reproductive potential of overwintering boll weevil, Anthonomus grandis grandis (Boheman), females collected from pheromone traps in September, November and January, fed for 1, 3, and 5 weeks on plant pollens, and then provided cotton squares, was determined in the laboratory at 27 ± 1°C, 65% RH, and a photoperiod 13 : 11 (L : D) h. Duration of pollen feeding by overwintering boll weevils did not significantly influence egg and feeding punctures, or puncture ratios (egg to total punctures) for any of the three months of parent weevil collections when provided cotton squares on a daily basis. However, punctures and puncture ratios are significantly different when comparing mean data between months of boll weevil collections. When boll weevils were provided with cotton squares daily, the pre-ovipositional periods of female parents captured in September, November and January were 5, 9 and 14 days, respectively. The rate of eggs by females was significantly lower during November and January than September. Female parents collected in September produced a significantly higher percentage of eggs yielding adult progeny than those collected in November and January. Life table parameters indicated that net reproductive rate ( R _o) of boll weevil females collected in September was 1.2-fold higher than those collected in November and 10.7-fold higher than those collected in January. Except for testes size, no differences in male reproductive parameters were observed during the cotton-free period compared with males captured during mid-cotton (June). The number of oocytes in the ovarioles and the number of oocytes containing yolk were significantly lower during September, November and January compared with June. The reproductive potential of overwintering boll weevil females collected in different months is an important consideration in determining the success of any control strategy.     

Semiochemical mediation of oviposition by the phlebotomine sandfly Lutzomyia longipalpis

Abstract. Extracts of rabbit food, hay and rabbit faeces elicited a positive oviposition response from gravid female Lutzomyia longipalpis sandflies (Diptera: Phlebotominae). Combined extract of rabbit food and oviposition pheromone had a synergistic effect on sandfly egg-laying, greatly increasing the number of eggs laid and resulting in a highly targeted response. Individually tubed flies, exposed to the combined extract, were shown to be 3.5 times more likely to survive oviposition and laid 2.5 times more eggs than control flies. A laboratory oviposition trap baited with the combined extract was tested in a cage and caught 31 (62%) of 50 gravid L.longipalpis over a 72h period.     

The Immediate Source of the Oviposition-Deterring Pheromone Produced by Larvae of Adalia bipunctata (L.) (Coleoptera, Coccinellidae)

As is the case for other insects ovipositing on or in resources that are limited in time and/or space, the two-spot ladybird beetle, Adalia bipunctata (L.) produces an oviposition-deterring pheromone (ODP), which is produced by the larval stages. Foraging larvae touch the substrate with their tarsi and the anal disk on the tenth abdominal segment. The aim of this paper was to determine whether the ODP produced by larvae was deposited by the tarsi or the anal disk. Fourth instar larvae either had their anal disk and tarsi, or anal disk, or tarsi coated with a water-soluble mounting medium. Larvae so treated were allowed to walk on filter paper that was subsequently presented to gravid females. The tracks of larvae that had both their tarsi and anal disk masked did not inhibit oviposition. However, the tracks of larvae that had only their tarsi masked significantly inhibited oviposition but those of larvae that had only their anal disk masked did not. It is concluded that the ODP is deposited on the substrate by the anal disk on the tenth abdominal segment of larvae.     

Evaluation of puncture types as indicators of boll weevil (Coleoptera: Curculionidae) oviposition in cotton squares

Reproductive boll weevil populations are typically identified by the presence of a frass seal and protuberance at the oviposition site in cotton squares. However, despite the occurrence of other oviposition puncture seal types and their use in previous fecundity studies, the relationship of these respective puncture seal types and oviposition has not been clearly examined. In this study, newly eclosed females (相似文献   

Deterrent activity of plant lectins on cowpea weevil Callosobruchus maculatus (F.) oviposition

A set of 14 plant lectins was screened in a binary choice bioassay for inhibitory activity on cowpea weevil Callosobruchus maculatus (F.) oviposition. Coating of chickpea seeds (Cicer arietinum L.) with a 0.05% (w/v) solution of plant lectins caused a significant reduction in egg laying. Control experiments with heat inactivated lectin and BSA indicated that the observed deterrent effects are specific and require carbohydrate-binding activity. However, no clear correlation could be established between deterrent activity and sugar-binding specificity/molecular structure of the lectins. Increasing the insect density reduced the inhibitory effect of the lectins confirming that female insects are capable of adjusting their oviposition rates as a function of host availability.     

Effect of marking pheromone on clutch size in the Mediterranean fruit fly

Abstract Using acridine orange to selectively stain eggs, we showed that wild-collected female Mediterranean fruit flies (Ceratitis capitata Wiedemann) laid fewer eggs per clutch in fruit previously infested with eggs than in uninfested fruit. This effect is apparently attributable to marking pheromone deposited by females after oviposition: clutch size on fruit infested with eggs but free of marking pheromone was not statistically different from that on uninfested fruit. Clutch size on uninfested fruit on which marking pheromone was artificially transferred was significantly lower than that on uninfested and untreated fruit. Marking pheromone had a comparable though not statistically significant effect on the clutch size of females originating from a strain maintained in the laboratory for several hundred generations.     

Mechanism and effectiveness of safflower oil against female Queensland fruit fly Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), infests many horticultural fruit crops in the eastern part of Australia. Farmers usually apply synthetic insecticides to control this pest. Little is known on the use of plant products especially vegetable oils for fruit fly control although they are considered to be safer than synthetic insecticides. In this study, safflower oil was investigated for its mechanism and effectiveness against female B. tryoni. In a laboratory test, safflower oil treatments (2.5 and 5.0 ml l^?1) reduced the number of fly punctures on treated artificial fruits, no matter whether pre‐punctures were present or absent. Safflower oil treatments also reduced the number of fly landings and eggs laid, but only when the treated artificial fruits were without pre‐punctures. These results confirmed that safflower oil is active against female B. tryoni mainly by preventing this fruit fly from making oviposition punctures, not by discouraging them from depositing eggs or by repelling them. The slippery nature of safflower oil is considered to be responsible for a reduction in the susceptibility of artificial fruit to fruit fly punctures. Further investigation using fruit‐bearing tomato plants (a no‐choice test) in a glasshouse situation revealed that safflower oil application at concentrations of 10 and 15 ml l^?1 reduced the number of oviposition punctures but failed to reduce the number of eggs laid. To increase efficacy of safflower oil under field conditions, multiple tools may be needed to reduce fruit fly populations and oviposition behaviour, such as the addition of trap‐crops, provision of artificial oviposition sites, or mixing the insecticides with the oil.     

Evolution of cannibalism and female's response to oviposition-deterring pheromone in aphidophagous predators

1.  Egg cannibalism by larvae is common in Coccinellidae and is known to be advantageous for the cannibals. Furthermore, larvae of aphidophagous ladybirds usually produce an oviposition-deterring pheromone (ODP), which inhibits oviposition by adult females. It has been proposed that the response to ODP has evolved because of the high costs of cannibalism. However, this has never been formally proved.
2.  In this paper, we study the theoretical evolution of this system. We first look at the conditions under which cannibalism and the response to ODP can evolve. Subsequently, we examine the occurrence of polymorphism both in the production of larval tracks and in the sensitivity of females to specific pheromones.
3.  The models predict that the amount of cannibalism should not depend on prey density and that evolution should lead to a continuous increase in cannibalism, and consequently larvae should always cannibalize eggs when possible. In response to the cost of cannibalism, ODP recognition can evolve, so that females avoid laying eggs in patches of prey already occupied by conspecific larvae. The result is an arms race between larvae and adult females, which favours a diversification of ODP pheromones. Our models show that: (i) females should be able to recognize mixtures of hydrocarbons rather than a single molecule; and (ii) females should be more sensitive to the tracks of their own offspring than those of non-related larvae.