Effect of Prior Experience in Finding and Accepting Plant and Oviposition in Several Species of Phytophagous Insects

ABSTRACT

I will discuss several species of phytophagous insects (Rhagoletis pomonella, Battus philenor, Bactrocera 
tryoni, Pieris rapae, Callosobruchus maculatus, Dacus dorsalis) and influence of prior (learning) 
experience to find and accept host plant. It will be discussed in relation to insect ability to learn visual and 
chemical stimuli of resources and insect propensity to form host races. In most cases the insect must 
'evaluate' and associate visual (spatial, light intensity and reflectance, shape) tactile and chemical (contact 
chemical, olfactory) information .What characters of the host are associated with the development of the 
response? In some cases it is fruit size and the surface chemistry which counts,  but in other it is 
association of visual cues with relevant characteristics of the host plant. These characters will be discussed 
through examples. Associative learning in egglaying site selection has been proved to be possible and 
important in several phytophagous insect species (such as Rhagoletis pomonella, Battus philenor, etc). 
Acceptance or rejecting of oviposition site (fruit) for egglaying after alighting on fruit is affected by fruit 
chemical and physical properties and the nature of prior ovipositional (learning) experience of insects with 
oviposition site. I will explain this through appropriate example. A description of some experimental 
evidence of experience-induced changes of oviposition preferences in a few phytophagous insect species 
will be given. The magnitude of an effect of experience, could depend on a female's original host  
specificity; generalist  genotypes may more likely to modify their egg-laying behavior in response to recent 
encounters with host plant.

In theory learning in acquisition of egglaying sites could occur during one or more phases of the 
acquisition process: finding the habitat, finding the plant within the habitat, finding a prospective egglaying 
site within a plant, examining the prospective egglaying site, and oviposition. Detailed investigation of the 
influence of learning during one or more of the  first three phases has been carried out in phytophagous 
only on Battus, Ceratitis and Bactrocera fruit flies.

INTRODUCTION

Insect  behavior was generally thought to be determined largely by closed genetic programs leaving little 
room for learning in behavioral development. This has changed over the last decades, especially since the 
highly developed learning ability of social Hymenoptera has been demonstrated. The number of 
publications dealing with learning in phitophagous species is also increasing rapidly. Several species of 
phytophagous insects have been shown to learn characteristics associated with acquiring food, mates or 
egglaying sites. A growing body of evidence shows that various behaviors governing resource use in 
insects may be influenced by the previous experience of individuals. In recent years, for instance, it has 
been found that prior exposure to a particular resource often enhances a female's tendency to oviposit on 
that type of resource. This is known to occur in wasps, flies, beetles and butterflies. In addition, 
preovipositional settling behavior, whether mediated by chemical or visual cues, has also been shown to 
be positively influenced by previous experience in wasps, butterflies and flies.

An intriguing finding, in the few cases where it has been sought, is that the degree to which preferences 
for specific resources may be modified by experience is age dependent. Feeding preferences of stick 
insects are more labile in nymphs than in adults, previous experience affects habitat selection more in 
young than in old ants, and newly emerged wasps show a greater modification of oviposition behavior by 
previous experience than do older wasps. 

A large number of variables may shape the manner in which an insect searches for and assesses the value 
of an essential type of resource such as food, a mate and egglaying site. These variables include genetic 
characteristics of the insects that affect its perception of environmental information and its locomotory 
pattern non- genetic that affect the internal state of  the insect with respect to propensity to respond to 
information from resource stimuli, and environmental factors that determine availability of resources.
  For phytophagous insects, the habitat can be defined as the host plant itself. Such insects appear to be 
particularly likely to undergo sympatric divergence in preference for alternative host species i. e., in habitat 
preference. Host preferences of phytophagous insects often vary genetically within  or between 
population. A second source of variation in host choice is experience. Insects of several orders undergo 
adaptive changes in behavior as a result of experience (that is, learning in its broadest sense). Learning is 
durable and usually adaptive modification of an animal's behavior traceable to a specific experience in an 
individuals life.

DISCUSION

1) Callosobruchus maculatus (Coleoptera: Bruchidae) 

Female of C. maculatus lay eggs singly on seeds of several of legumes, especially in the genus Vigna. 
Oviposition is stimulated by chemical cues on the seed surface and discrimination between host species is 
mediated largely by sensory receptors on the maxillary palps. Genetic variation in the host choice has been 
observed both within and among populations. Geographic strains differed in their thresholds of host 
acceptance (i. e., their host specificity) but not in the rank order of host preference (Singer, 1992).

Oviposition preferences of C.maculatus may depend on experience. When females were exposed to a 
highly acceptable host (black -eyed pea) after adult emergence, they appeared to develop an exaggerated 
aversion to a less acceptable host (chickpea).This effect of experience may have been confounded by 
variation in female egg load. Females exposed to black -eyed pea laid more eggs during the conditioning 
period than females exposed to chickpea did, and one group of females conditioned on black-eyed pea 
subsequently laid relatively few eggs on both chickpea and black-eyed pea (Mark,1982).
Mung bean and azuki bean (V.angularis )were chosen as experimental hosts. Azuki bean is generally 
preferred over mung bean, but the two hosts are accepted at statistically similar rates by some beetles 
populations (Wasserman ,1986). Azuki beans are larger than mung beans. This size differences may affect 
absolute acceptance rates in C. maculatus but should not affect comparisons between females with 
different experience (Mitchell,1975).

Experiments with naive females (the egg-laying preferences of females with no prior exposure to mung 
bean or  azuki bean and no egg-laying experience) established genetic differences in host specificity among 
geographic strains of the seed beetle C. maculatus; some females strongly preferred azuki bean over mung 
bean, and others failed to discriminate between two hosts. It was examined whether such congenital 
differences affect the degree to which host preference can be modified by experience. In choice tests, 
previous exposure to azuki bean increased the proportion of eggs laid on that host, but only in strains with 
a relatively low host specificity. This result conforms to a pattern obtained from interspecific comparisons, 
that generalists are more susceptible to the effects of experience than specialists.

Under more realistic,  no-choice conditions,  egg laying experience affected oviposition rates mostly in 
strains with high host specificity; however these experiments could not distinguish between the effect of a 
female's experience per se and her physiological state, i.e. egg load [5]. This study has shown that the 
effect of experience varies among strains   does not mean that strains differed in the propensity to learn. 
Results implied that the importance of experience in host choice can depend on the existing level of host 
specificity in particular population.

With regard to Coleoptera, very few examples of learned oviposition preference have been found, all with 
a bruchid species, C.maculatus. The plant species tested differed: Cajanus cajan and Phaseolus radiatus in 
the earlier study, and Vigna unguiculata and Cicer arietinum in the later one. A learning process is possible 
in these studies, since in addition to the effect of inherently preferred host seeds, other specific stimuli 
such as the seed's surface curvature, chemical constituents of the seed coat, oviposition marking 
substances, and seed size can all serve associating reinforces, and therefore influence the response [6].

2) Pieris rapae (Lepidoptera: Pieridae)

Learning has been shown to occur in P. rapae. Traynier & Truscott (1991) have shown that P.rapae can 
associate the color of a disk with the presence of host phytochemicals (sinigrin or glucobrassicin). In 
addition, a preference was observed in subsequent tests for the visual stimuli (color) learned by 
association. However, Traynier (1987) reported that from preliminary experiments of 24 h duration, P. 
rapae did not associate leaf shape characteristics with the presence of sinigrin.

Furthermore, P.rapea is unable to learn to associate negative stimuli with color. Experiments in which P. 
rapea was offered a choice between six white discs for oviposition, on three different occasions. In the 
first and third test, two discs were treated with sinigrin solution and the remainder with water, while in the 
second test two discs were treated with water, two with sinigrin solution and two with chlorogenic acid. 
The egg distributions from the first and third trials were similar with most eggs laid on sinigrin solution 
-treated discs and the remainder evenly distributed on water discs. In the second test, the chlorogenic acid 
discs failed to elicit oviposition, receiving very few eggs, whereas, the water and sinigrin discs both 
received eggs. Chlorogenic acid influenced behavior only instantaneously as a deterrent and failed to 
influence learning[1].

Traynier demonstrated a long term change in the oviposition behavior of the cabbage butterfly induced by 
contact with plants. Gravid females were placed in cages and were allowed contact either with cabbage or 
lettuce discs for 30 min, then deprived of any leaf discs for 24 and 72 h, and finally retested on cabbage or 
lettuce. Cabbage-experienced butterflies landed on cabbage and laid eggs, whereas on lettuce they 
frequently moved from disc to disc but rarely laid eggs. The females experienced on cabbage landed more 
frequently on lettuce than those becoming experienced on lettuce, but few eggs were laid. Those that 
experienced lettuce on each occasion showed a low level of responsiveness in both tests, because the 
tendency to land decreased after the first two minutes. It could be that the females gained oviposition site 
imprinting or induction and had learned to respond to green disks  but it is also possible, as suggested by 
Traynier, to explain it by sensitization [6].

Insects have learned how to stand in the best position on the flower, and how far in what direction to insert 
their proboscides ( Darwin, 1876). Darwin hypothesized that flower constancy in insects that feed on 
nectar results from the need to learn how to extract nectar from a flower of a given species. In laboratory 
tests, Pieris rapae, showed flower constancy by continuing to visit flower species with it had  experience.  
The time required by individuals to find the source of nectar in flowers decreased with successive 
attempts, the performance following a learning curve. (Fig 1). Learning to extract nectar from a second 
species interfered with the ability to extract nectar from the first. Insect that switch species thus experience 
a cost in time to learn. These results support recent suggestions on the importance of learning in animal 
foraging [12]. 

3) Dacus dorsalis

Compared with females of Rhagoletis, Anastrepha and Ceratitis tephritid flies, Dacus dorsalis females 
seem less able to bore through the skin of on -tree host  fruit with the ovipositor.  Rather, D. dorsalis 
females often use preexisting punctures made by other tephritids or wounds made by birds or other agents 
for access to the fruit flesh, where the eggs are deposited. The hypothesis was that D. dorsalis females 
might respond positively to odor as well as visual properties of individual fruit, particularly freshly 
punctured fruit. The question is whether the propensity of D. dorsalis females to alight on kumquats or 
apples was influenced by previous experience with these fruit and what sorts of host fruit cues modified 
subsequent female responses to these fruit.

Mature oriental fruit fly females, D. dorsalis, from a population cultured on host fruit in the laboratory for 
one generation responded positively  to visual  stimuli of individual kumquat (Fortunella japonica) and 
apple (Malus pumila) host fruit or models of these fruit hung from branches of potted trees in field 
enclosures. Response was greater when fruit visual stimuli exist in combination with odor stimuli (as in 
unpunctured natural fruit)  and even greater when natural fruits are freshly punctured, which confirms 
earlier hypothesis. Although, D. dorsalis females do refrain from ovipositing in punctures containing 
conspecific or heterospecific larvae, they do not refrain from laying eggs in uninfested punctures or 
punctures containing only eggs (Prokopy,1989).

When females were exposed for 3 days to natural kumquats or apples on trees and subsequently released 
individually onto trees harboring one or the other of these fruit types, a significantly greater proportion of 
females  exposed to kumquats than females  exposed to apples or females  not exposed to any fruit visited  
kumquats. Possibly kumquats are somewhat inconspicuous in appearance to females lacking prior 
experience finding kumquats. Once such experience has been obtained, apparently it is not quickly 
forgotten. Females exposed to kimquats for at least 3 days followed by at least 3 days of exposure to 
apples retained ability to find kumquats. Compared with females exposed to apples for 3 days or with 
naive females, females exposed to kumquats for 3 days exhibited no less ability to find apples but did 
significantly refrain from accepting apples for oviposition. Females were exposed to natural kumquats or 
apple for 3 days and tested for response to inanimate models of either the same color and size as natural 
kumquats (orange,20-mm diameter) or apples (green, 75-mm diameter) or model of same color but 
opposite size. Results suggest that fruit size is the principal character learned and used  in finding 
kumquats, which apparently are somewhat inconspicuous to an inexperienced foraging D. dorsalis female 
[4].

The studies of C. capitata  flies suggest that fruit size is a principal character learned by fruit -seeking 
females during within -tree search, with fruit color and odor apparently being of lesser or no importance. 
Among other phytophagous insects, host experience  enhances upwind response to host -plant odor in 
Leptinotarsa beetles, Schistocerca nymphs, and Bruchophagus seed chalcids. Color and/or light intensity 
cues are learned by Heliconius  in finding nectar source or egglaying sites. Besides, D.dorsalis, females of 
R. pomonella, C. capitata, and B. tryoni are capable of learning to accept fruit for egg laying.  

4) Bactrocera tryoni (Diptera;Tephritidae)

Intensive study of population of B. tryoni  under semi-natural and natural conditions has revealed that a 
source of exogenous protein for females in Queensland is bacteria that occur on the surface of host fruit in 
infested trees. The odor of such "fruit -fly-type" bacteria is known to attract B. tryoni females a distance of  
at least several centimeters.

Using caged host trees on which food and oviposition sites were manipulated, the foraging behavior of 
B.tryoni females in relation to state of fly hunger for protein (presence or absence of bacteria as a source of 
protein), degree of prior experience with host fruit, and quality of host for oviposition was investigated. 
One task to determine was whether it is immature or mature B. tryoni females that are responsible for 
initially inoculating host fruit surfaces with fruit-fly- type bacteria. It was found that 3-week -
old immature females  provided with sucrose, but deprived of  protein from inclusion had a much greater 
propensity than 3-week-old protein-fed mature females to visit vials containing bacteria. In the absence of 
associated bacteria in vials, immature females had a much  lower propensity than mature females to visit 
host fruit. In the presence of bacteria in vials, propensity of immature and mature females to visit fruit was 
about equal. Mature (but not immature) females were more inclined to visit fruit that ranked higher for 
oviposition (nectarines) than fruit that ranked lower (sweet oranges).

Mature females that attempted oviposition during a single 3- min exposure period to a nectarine prior to 
release were much more likely to find a nectarine after release on a tree than were mature females naive to 
fruit or immature females with or without prior contact with fruit. The results of the experiment showed 
that prior experience with nectarines did not affect the propensity of either mature or immature B.tryony to 
alight on an odorless inanimate models of fruit that closely mimicked the  visual properties of nectarines. 
This suggests also that it is host -fruit chemical stimuli that are learned by females during  a single 
ovipositional bout, and that elicit subsequent search for fruit emitting similar chemical stimuli [8].

5) Battus philenor

The effect of learning has been investigated in the butterfly  species  including P. rapae, C. p. eriphyle and 
Battus philenor. 

In a study of B.philenor searching behavior ,there were two species: Aristolochia reticulata and 
A.serpentaria, of host plant in the herbaceous vegetation . These two hosts differ in leaf shape: A.reticulata 
has broad ovate leaves whereas A.serpentaria has long narrow parallel-sided leaves. It was observed that 
B. philenor females appeared to be highly selective in their response to leaf shape, with females searching 
and  alighting preferentially on either narrow-leaved or broad-leaved hosts but not both simultaneously. 
Females did not change their search mode during a 30min observation period. Females alighting and 
ovipositing on a host plant with a leaf shape different to that being searched for then adopted that leaf 
shape as their search mode (Rausher,1978).

Females of B.philenor responded preferentially to a particular leaf shape during search and had a higher 
rate of encounter of that shape. Females with a stronger preference for a particular leaf shape discovered a 
greater proportion of host plants with that leaf shape than did females with a weaker 
preference. (Rausher,1978).

The conditioning of B.philenor to leaf shape through association with host plant phytochemical cues in 
laboratory studies has been investigated by Papaj (1986).It was found that the host leaf shape to which a 
gravid females was exposed had a marked effect on the leaf shapes on which she alighted. These 
differences in alighting preference were significant and contact only was necessary to train the 
butterflies.[1]

The training of B. philenor to leaf shape was easily reversed when a female exposed to host plants of a 
particular leaf shape was exposed to host plants with a different leaf shape. With a single exception, all 
females exposed first to one host plant species adopted a search mode for the second host plant to which 
they were exposed. The association between the final search mode and re-training of the insect to the host 
is significant (Papaj,1986). The results of Papaj (1986) and Rausher (1978) would seem to show that B. 
philenor can learn to search preferentially for a particular leaf shape by conditioning of perception; defined 
by Papaj (1983), as any effect of experience that improves the probability of detecting a stimulus.

The frequency with which B.philenor females alighted on particular kinds of conspecific plants was 
apparently modifiable through experience (Fig. 2). Although females first  alighted on large plants 
regardless of age category in proportion to their abundance, they eventually alighted significantly more 
often on larger young plants as time went on. Young plants received egg clusters more often after a female 
alighted than did old plants, and large plants always received egg clusters more often after a female 
alighted than did small plants (Table,1) [10].

6) Rhagoletis pomonella (Diptera:Tephritidae)

For R.pomonella as well as many other frugivorous tephritids, the size, color, and shape of fruit all play a 
significant role in fly ability to find individual fruit for oviposition. R. pomonella flies are known to find 
large (8cm), red-colored, or spherical fruit (or mimics) more readily than smaller, green-colored, or 
semispherical fruit, or mimics. (Prokopy,1986).

R. pomonella females proved capable of finding spherical, red medium-size (55-mm) apples or spherical, 
red,  small (18-mm) hawthorns to an approximately equal extent irrespective of whether they had prior 
ovipositional experience for 3 days with fruit of these types or with green apples or green hawthorns. 
Females proved significantly less capable of finding spherical, green, medium-size (55-mm) apples or 
spherical, green, small hawthorns (18-mm) when they had prior ovipositional experience for 3 days with 
red apples or red hawthorns compared with green apples or green hawthorns. This findings nonetheless 
suggest that green fruit may be less conspicuous to females whose prior ovipositional  experience had been 
with red fruit compared with green fruit. Alternatively, red fruit may constitute a higher-quality resource 
and females having information (from prior experience) that red fruit exist in the habitat may see but ignore 
green fruit.

Differences in size (or surface chemistry) of fruit but not differences in color among green and red 
hawthorn and green and red apples had a significant negative effect on the propensity of alighting R. 
pomonella females to bore into fruit of a type with which they had no prior experience.

Three bouts of experience with alighting upon and ovipositing  into fruit over a period of about 1h had no 
effect on females ability to find unfamiliar fruit but did reduce propensity to bore into unfamiliar fruit [3]. 
The length of exposure, (i.e. the quantity of experience) is important. In contrast, after only a single bout 
of host alighting and ovipositional experience, B.tryoni females demonstrated  a significantly enhanced 
ability to find a familiar fruit (Prokopy,1991). R.pomonella females use fruit visual stimuli but not fruit 
odor as cues for finding individual fruit, whereas B.tryoni females use both of these types of cues.

Females of R.pomonella exposed to particular host fruit species-apple or hawthorn in a  field cage 
oviposited at a higher rate in test fruit of that species than did inexperienced females or females exposed to 
other species. Females exposed to a particular host fruit species also tended to remain longer in test trees 
harboring fruit of that species than did inexperienced females or females exposed to the other species. 
Prior adult experience thus alters two components of habitat preference in the R.pomonella: oviposition 
preference and habitat fidelity [14].

REFERENCES

1. Hern, A., Jones, G.E., and Mckinlay, R.G. (1996). A review of pre-oviposition behavior of the small 
cabbage white butterfly, Pieris rapae (Lepidoptera:Pieridae). Ann.appl.Biol.128:349-371.

2. Feder,J.L., Reynolds,K., Go,W., and Wang, E.C. (1995).Intra-and interspecific competition and host 
race formation in the apple maggot fly, Rhagoletis  pomonella (Diptera:Tephritidae).Oecologia101:416-
425.

3. Prokopy, R. J., Bergweiler ,C., Galarrza, L.,  and Schwerin, J. (1994). Prior experiance affects the 
visual ability of  Rhagoletis pomonella flies (Diptera: Tephritidae)to find host fruit. J.Insect Behav.7: 663-
678.

4. Prokopy, R. J., Green, T. A., and Vargas, R. I. (1990).Dacus dorsalis flies can learn and accept host 
fruit. J. Insect Behav.3:663-675

5. Chiu,Yuan-ju., and Messina, F. J. (1994).Effect of experience on host preference in Callosobruchus 
maculatus (Coleoptera: Bruchidae): variability  among populations.J.Insect Behav.7:503-515

6. Szentesi,A., and Jermy,T. (1990)The role of experience in host plant choice by phytophagous 
insects.In 
Bernays,E.A. (ed.),Insect-Plant Interactions,Vol .II,CRC Press,Boca Raton,FL,pp 39-74

7. Papaj, D. P ., Opp, S. B., Prokopy,R. J., and Wong, T. T.Y. (1989). Cross - induction of fruit 
acceptance by the medfly Ceratitis capitata :  The role of fruit size and chemistry.J. Insect Behav.2:241-
253.

8. Prokopy, R. J, Drew,R. A.I, Sabine,B.N.E, Lloyd,A.C, and Hamacek, E. (1991). Effect of 
physiological and experiential state of Bactrocera tryoni flies on intra-tree foraging behavior for food 
 (bacteria) and host fruit. Oecologia 87:394-400.

9. Prokopy,R.J., and Luna,I.G. (1995).Behavioral differences between hawthorn-origin and apple 
-origin 
Rhagoletis pomonella flies in patches of host trees. Entomologia Experimentalis et Applicata74:277-282.

10. Papaj,D.R and Rausher,M.D (1987).Components of conspecific host discrimination behavior in the 
butterfly Battus philenor. Ecology 68:245-253.

11. Jaenike,J. (1988).Effect of adult experience on host selection in insect: Some experimental and 
theoretical results. J.Insect Behav.1:3-16.

12. Lewis,A.C. (1986).Memory constraints and flower choice in Pieris rapae. Science 232:863-864.

13. Jaenike,J., and Papaj,D.R. (1992).Behavioral plasticity and patterns of host use by insects.In 
Papaj,D.R., and Lewis,A.C (eds.),Insect learning, Chapman and Hall,New York, pp.245-264.

14. Papaj,D.R, and Prokopy,R.J. (1988).The effect of adult experience on components of habitat 
preference in the apple maggot fly (Rhagoletis pomonella).Oecologia76:538-543.

15. Prokopy,R.J.,Averill, A.L.,Cooley,S.S., and Roitberg,C.A. (1982). Associative learning in 
egglaying site selection by apple maggot flies.Science.218:76-77.

16. Papaj,D.R. (1986).Conditioning of leaf -shape discrimination by chemical cues in the butterfly Battus 
philenor.Anim.Behav.,34:1281-1288.

17. Mark,G.A. (1982).Induced oviposition preference, periodic environments and demographic cycles in 
the bruchid beetle Callosobruchus maculatus. Entomol. Exp.Appl.32:155-160.