Oligophagous Species Research Articles

Benefits and risks of introducing exotic macro‐biological control agents into Europe1

Biological control of insects — the use of natural enemies to reduce pest numbers — has been applied on a worldwide scale for more than 100 years and its use has considerably increased during the past decades as it offers a sustainable, economical and environmentally attractive alternative to chemical pest control. In biological control, locally occurring natural enemies are used or alien species are imported. Until now, introductions of hundreds of species of insect natural enemies have not led to environmental problems when a procedure of selection, importation and release was carefully applied. In contrast, many intentional and unintentional introductions of plants and phytophagous animals have resulted in very negative effects on the environment. Several early biological control introductions, mostly of generalist, large predators (e.g. vertebrates, birds and toads) and usually not supervised by biological control experts, led to unintended negative effects on native species. For insect biological control executed by experts, examples of unintended, harmful effects are not known. Selected natural enemies are usually specific, mono‐ or oligophagous species of parasitoids and predators. To prevent making mistakes in the future, pre‐introductory evaluation of natural enemies is advocated, including a step where their potential negative effects are studied. Examination of the literature, taxonomic research and host acceptance experiments are used in such studies to estimate negative effects.

HOST-PLANT SWITCHES AND THE EVOLUTION OF CHEMICAL DEFENSE AND LIFE HISTORY IN THE LEAF BEETLE GENUS OREINA.

Insect-plant interactions have played a prominent role in investigating phylogenetic constraints in the evolution of ecological traits. The patterns of host association among specialized insects have often been described as highly conservative, yet not all specialized herbivorous insect lineages display the same degree of fidelity to their host plants. In this paper, we present an estimate of the evolutionary history of the leaf beetle genus Oreina. This genus displays an amazing flexibility in several aspects of its ecology and life history: (1) host plant switches in Oreina occurred between plant families or distantly related tribes within families and thereby to more distantly related plants than in several model systems that have contributed to the idea of parallel cladogenesis; (2) all species of the genus are chemically defended, but within the genus a transition between autogenous production of defensive toxins and sequestration of secondary plant compounds has occurred; and (3) reproductive strategies in the genus range from oviparity to viviparity including all intermediates that could allow the gradual evolution of viviparity. Cladistic analysis of 18 allozyme loci found two most parsimonious trees that differ only in the branching of one species. According to this phylogeny estimate, Oreina species were originally associated with Asteraceae, with an inclusion of Apiaceae in the diet of one oligophagous species and an independent switch to Apiaceae in a derived clade. The original mode of defense appears to be the autogenous production of cardenolides as previously postulated; the additional sequestration of pyrrolizidine alkaloids could have either originated at the base of the genus or have arisen three times independently in all species that switched to plants containing these compounds. Viviparity apparently evolved twice in the genus, once without matrotrophy, through a retention of the eggs inside the female's oviducts, and once in combination with matrotrophy. We hypothesize that the combination of autogenous defense and a life history that involves mobile externally feeding larvae allowed these beetles to switch host plants more readily than has been reported for highly conservative systems.

Intra- and interspecific predation on four life stage groups by the adult females of Metaseiulus occidentalis, Typhlodromus pyri, Neoseiulus fallacis and Amblyseius andersoni

Do adult females of oligophagous species such as Neoseiulus fallacis (Garman) and Metaseiulus occidentalis (Nesbitt) show less intra- and interspecific predation on phytoseiids when other foods are scarce than polyphagous species such as Amblyseius andersoni Chant and Typhlodromus pyri Scheuten? We caged single adult females of each species without food with ten of their own eggs or larvae, with ten eggs or larvae of the other species or with ten nymphs or adult females of M. occidentalis (T. pyri for M. occidentalis). We assessed the ambulatory activity, survival time, egg levels and prey loss in each test. Polyphages (in particular T. pyri) lived longer than oligophages (in particular N. fallacis) without food. The small T. pyri detected its own stages and benefited most by feeding on small active stages of other species. Amblyseius andersoni, the largest mite, fed and gained the most of any species when held with nymphs and female adults. Metaseiulus occidentalis fed on eggs of all four species to enhance survival. The large hyperactive N. fallacis gained the least from these behaviours. Each mite seemed uniquely adapted to survive conditions of scarce prey and these behaviours may explain their roles in phytoseiid mite complexes. Overall, oligophagous adult females fed less and gained less by feeding on phytoseiids than did polyphagous adult females.

Effects of recent experience on foraging in tephritid fruit flies

In field-cage studies, we investigated how the foraging behavior of tephritid fruit flies is modified by experience immediately prior to release on host plants. We observed females of a relatively monophagous species,Rhagoletis mendax (blueberry maggot fly), an oligophagous species,Rhagoletis pomomella (apple maggot fly), and a polyphagous species,Ceratitis capitata (Mediterranean fruit fly). Just prior to release on a host plant, the following kinds of stimuli were supplied: (1) single oviposition in a host fruit, (2) contact with 20% sucrose, (3) contact with a mixture of protein food (bird feces and sucrose), (4) contact with water, and (5) a walk over a host-plant leaf. When flies foraged on host plants without resources, search was most intensive (as measured by number of leaves visited) following a single oviposition in fruit, but residence time generally was the same following exposure to sugar, protein, and fruit stimuli.Rhagoletis mendax andC. capitata females visited the fewest leaves following exposure to water or host leaves, whereasR. pomonella foraged equally intensively following exposure to food stimuli, water, or leaves. On host plants containing resources (fruit and protein food), a single oviposition dramatically increased the number of females of all three species that found fruit compared to females that received experience with food, water or foliar stimuli. We found no significant effect of recent brief experience with any of the stimuli on subsequent attraction to protein food. Overall,C. capitata exhibited a higher propensity to abandon host plants than eitherR. mendax orR. pomonella. We suggest that this may reflect adaptations to differences in distribution of host plants in nature, strategies of dispersal, and host range.

Costs of Inducible Defense: Protein Limitation, Growth, and Detoxification in Parsnip Webworms

Although xanthotoxin, a linear furanocoumarin, is toxic to a wide variety of lepidopterans, the parsnip webworm, Depressaria pastinacella (Lepidoptera: Oecophoridae), is restricted to feeding on only two genera of Apiaceae, both of which contain large quantities of this toxin. The cost of cytochrome P450—mediated detoxification of xanthotoxin by this oligophagous species was examined in two artificial diet experiments. In the first experiment, growth rates, silkspinning rates, and detoxification capacity of larvae were measured after they had consumed diets ranging in protein content from 0 to 100% of the amount required for maximum growth. As protein became progressively more limited, growth rates declined progressively while silkspinning rates and detoxification capacity remained unchanged; only when dietary protein was completely absent did silkspinning rates and xanthotoxin metabolism rates decline. These findings suggest that xanthotoxin detoxification capacity is maintained at the expense of growth. In the second experiment, growth rates, silkspinning rates, and xanthotoxin metabolism were measured in larvae that consumed diets with or without xanthotoxin in the presence or absence of protein. As in the previous experiment, the absence of protein led to significant reductions in growth, silkspinning, and detoxification. The presence of xanthotoxin in the diet resulted in an increase in the rates of xanthotoxin metabolism and silkspinning but did not have any effect on growth rates. Inasmuch as there were no interactions between protein and xanthotoxin treatments, induction of xanthotoxin metabolism by xanthotoxin was not affected by protein limitation. The fact that xanthotoxin metabolism is induced almost threefold in the absence of dietary protein, conditions that result in reduction of growth rates by almost 80%, is also consistent with the greater importance of detoxification capacity relative to growth over the short term. Due to its highly oligophagous habits, the parsnip webworm is unlikely to encounter host plants tissue entirely lacking furanocoumarins; circumstances under which the inability to respond to the presence of xanthotoxin in the diet by increasing rates of its metabolism may never exist. Thus, maintaining high and inducible levels of cytochrome P450—mediated xanthotoxin metabolism may be regarded as one of the costs associated with the highly specialized diet of D. pastinacella.

A comparative life history study of immature Amblyseius fallacis, Amblyseius andersoni, Typhlodromus occidentalis and Typhlodromus pyri (Acari: Phytoseiidae) with a review of larval feeding patterns in the family

Survival, developmental time, activity, feeding rates, and other biological aspects of immatures of Amblyseius fallacis, Amblyseius andersoni, Typhlodromus occidentalis and Typhlodromus pyri were examined in the laboratory in small arenas (2×2 cm) with different egg densities (0, 5, 10, 20 per 12 h) of the twospotted spider mite, Tetranychus urticae (Koch), at 25±1°C, ≈80% RH, and 16L: 8D photoperiod. Egg survival was high (86–100%) in all four species. Larval survival was similarly high except for T. occidentalis which all died in the absence of food. Survival rates of protonymphs and deutonymphs were also high except that up to 50% of A. andersoni died at 5 prey eggs per 1/2 day. Developmental time did not vary significantly with prey density and was similar for males and females in the oligophagous predators (A. fallacis and T. occidentalis), but was longer at lower prey densities and in females than males in the polyphagous predators (A. andersoni and T. pyri). In general, the time allocated to three active instars (=stases) decreased in the order: A. andersoni (81%), T. pyri (78%), A. fallacis (69%), and T. occidentalis (64%). The polyphagous predator species had a shorter larval stage and much longer deutonymphal stage than the oligophagous species. The proportion of time allocated to the protonymphal stage was the least variable among the four species. The interspecific differences in walking activities also appeared greater in larval and deutonymphal stages than in the protonymphal stage. The larvae of the two oligophagous predators (A. fallacis and T. occidentalis, walking activity averaging 36–49%) were more active than the two polyphagous predators (A. andersoni and T. pyri), which spent 80% or more time resting. In deutonymphs, walking activity increased in the order: T. occidentalis (14%), A. andersoni (27%), A. fallacis (43%) and T. pyri (59%). Larvae were more active during the first half of their life than the latter half. In general, most life history traits of immature A. andersoni, T. pyri, A. fallacis, and T. occidentalis are not associated with their phylogenetic relatedness or size, but with the feeding specialization of the predator species. Larval feeding patterns in Phytoseiidae are reviewed and a hypothesis about the evolution of larval feeding behavior in Phytoseiidae is proposed.

Phytophagous Insects Associated with Pistia stratiotes in Florida

During July 1985 to June 1986, we surveyed the arthropod fauna associated with Pistia stratiotes L., waterlettuce, in Florida. Plant samples were collected at 61 sites. Samples comprised a minimum of 20 waterlettuce rosettes. Invertebrates were removed from the plant sample using a submergence technique. Eighteen phytophagous species were recovered from P. stratiotes . Six of these species are known waterlettuce feeders. They include the moths Petrophila drumalis (Dyar), Synclita obliteralis (Walker), and Samea multiplicalis Guenee, the aphid Rhopalosiphum nymphaeae L., the leafhopper Draeculacephala inscripta Van Duzee, and the weevil Tanysphyrus lemnae (F.). Most of these insects are either stenophagous or polyphagous; none feed exclusively on waterlettuce. The paucity of specialists on waterlettuce in Florida contrasts sharply with the richness of oligophagous species in South America. This suggests that water lettuce is not a native species, despite observations of its occurrence in Florida as early as the mid-1700s.

Phytophagous Insect Faunas of Dicoria canescens and Iva axillaris, Native Relatives of Ragweeds, Ambrosia spp., in Southern California, with Analyses of Insect Associates of Ambrosiinae

This study completes a series of faunistic surveys of all genera and most species that compose the Subtribe Ambrosiinae of the Tribe Heliantheae (Asteraceae) in southern California. Phytophagous insects representing 7 orders, 30 families, 68 genera, and 77 species compose the insect fauna of Dicoria canescens Torrey & Gray in southern California. Similarly, phytophagous insects representing 7 orders, 25 families, 39 genera, and 47 species compose the insect fauna of Iva axillaris Pursh. Most insects on these native herbs are ectophagous, sap- and foliage-feeding insects. More than half, 38 (51%) of 74 of the identified species on D. canescens occur on other Ambrosiinae ( Ambrosia, Hymenoclea , and Xanthium spp.), as do 17 (46%) of 36 identified species on I. axillaris . Sixteen (21%) of the 74 species on D. canescens only feed on Heliantheae, including eight oligophagous species restricted to the Ambrosiinae and four monophages. On I. axillaris , 9 (25%) of the 36 species were restricted to the Heliantheae, including one oligophagous and three monophagous species. In total, 412 species of insects are now known to be associated with Ambrosiinae in southern California, 293 (71%) of which have been identified to species. Trophic, taxonomic, niche, and distributional characteristics of these phytophagous insects on Ambrosiinae are analyzed and compared with faunas of other species groupings and subtribes of native Asteraceae in North America and Europe. These findings also are reviewed and discussed relative to the biological control of ragweeds in North America and abroad.

Comparative study of the antennal sensilla of five species of root maggots: Delia radicum L., D. floralis F., D. antiqua Mg., D. platura MG. (Diptera : Anthomyiidae) and Psila rosae F. (Diptera : Psilidae)

A comparative study of the antennal sensilla of Delia radicum L., D. floralis F., D. antiqua Mg., D. platura Mg. (Diptera : Anthomyiidae) and Psila rosae F. Diptera Psilidae) is undertaken. For both sexes of each species, the type, distribution, and density of sensilla are determined. All 5 species have trichoid (olfactory) and grooved (olfactory) sensilla. Basiconica I (blunt) sensilla (olfactory) are found on each of the species examined, except D. platura. Basiconica II (tapered) (olfactory) and clavate (olfactory) sensilla are found only on Delia species. Also, only Delia species have single-chambered, dorsal pits, and these contain basiconic II pit sensilla (olfactory). Common to all 5 species is a multi-chambered ventral pit (olfactory). In the ventral pit, all 5 species have grooved pit sensilla (olfactory). In addition to this type of sensillum the Delia species have smooth-walled conical pit sensilla (hygro-/thermosensitive) and P. rosae has granular pit sensilla (hygro-/thermosensitive). Smooth-walled tapered pit sensilla (hygro-/thermosensitive) are found in D. radicum. Similarities and differences in the density of surface sensilla between dorsal and ventral funicular surfaces, male and female flies, and oligophagous (D. antiqua, D. radicum, D. floralis and P. rosae) and polyphagous (D. platura) species are compared. Several differences in sensillum density between the dorsal and ventral funicular surfaces are observed, but these do not fit into a consistent trend. Except for D. radicum, there are differences in sensillum density between male and female flies. For the oligophagous species, females have a greater sensillum density, whilst for the polyphagous D. platura males have a greater sensillum density. Comparisons between species show the greatest differences between the Delia species and P. rosae, and within the 4 Delia species, differences in sensillum density do not correlate with host range or body size.

Cytotoxic effects of α-terthienyl on the midgut of the tobacco hornworm, Manduca sexta

The toxic effects of sublethal doses of α-terthienyl, a secondary metabolite of Asteraceae, was studied on the fifth instar larvae of Manduca sexta following continuous feeding for 24 h. Localized areas of damage to midgut epithelial cells were observed with swelling and rupture of both columnar and goblet cells. However, the midgut appears to recover from this damage and continue normal development, suggesting the ability of an oligophagous species like M. sexta to repair and recover from the effect of these toxins.

Can Predation Lead to Narrow Food Specialization in Phytophagous Insects?

I can fully agree with Bernays and Graham that: (1) trade-off estimations have not proved advantage of specialists over generalists so far, (2) secondary plant compounds provide proximate but not ultimate cause for narrow host (3) evolutionary arms race analogy cannot fruitfully be applied to insectplant relationships, (4) deterrents do not betoken toxicity of plants, (5) secondary plant compounds cannot be regarded, first and foremost, as defenses against insects, (6) local host abundance is more a prerequisite for specialization than cause of it, and (7) views of specialization as enhancing mate location, reducing mortality from abiotic factors, or providing efficient attachment on plant may be valid only for special cases. However, authors' final conclusion, that predation might be the most important factor pushing insect herbivores toward narrow host range, does not seem to hold. One of their main premises is that host use is labile and, consequently, that current selective pressures may explain evolution of specialized habits. As proof they offer (a) restrictions on host-plant ranges of local populations in polyand oligophagous species, (b) recruitment of insect species to introduced plants, and (c) rapid adaptation of pest species to resistant cultivars. In none of three cases, however, do changes represent basic changes in host range. In cases (a) and (c), presence of a dominant or novel host plant simply selects for a certain genotype that happens to be preadapted to it, or in case (a) observed restriction may represent an experience-induced, and thus temporary, specialization (induced preference) that can occur only within innate host range (Jermy 1987). In case (b) asymptotic nature of recruitment curve itself (Strong et al. 1984) proves that adaptation to novel host is usually not a question of evolutionary time: only insect species recruited are those that harbored already preadapted genotypes. As soon as these are exhausted, recruitment ceases. Thus lability of host use is usually confined within fairly narrow host-plant limits. A further question also arises: how frequently do changes of host range occur in nature? In this connection it must be pointed out that, for example, members of several families of Lepidoptera feed exclusively on species of a single plant family (Ehrlich and Raven 1964); families of scale insects Kermesidae and Dactylopidae live exclusively on Fagaceae and Opuntia spp., respectively (Eastop 1978); a group of species of chrysomelid genus Crioceris, occurring mostly sympatrically in Palearctic region, are restricted to Asparagus spp. (Kaszab 1962); adults of as many as five hispine beetle species may occupy one scroll made of leaves of Heliconia spp. (Strong 1984); etc. Many similar examples can be given. They indicate that in all these insect taxa host range did not change much during process of speciation, which might have taken many millions of years. There is no reason to suppose that in meanwhile biotic and abiotic ecological factors did not change or that selective factors were and are same in whole area of distribution. Thus, conservatism of host range may be as common as lability. Naturally, degree of conservatism is variable and is obviously a fundamental genetic character of each group of insects. The idea propounded by authors that predation may play most important role in evolution host range is challenging, but one has to agree with authors' opinion that experimental studies are needed to prove its validity. The presently available, mostly circumstantial evidence, well reviewed by authors, is meagre. On other hand, it is almost common knowledge that most generalist predators do not hunt by plant species, which would be a prerequisite of leaving certain plant species as enemy-free space. For example, insectivorous birds hunt in forest by structure of trees, but not by their species (Krebs and Davis 1978). Carabid beetles select specific habitats independently of plant species therein (Thiele 1977). In searching for aphids, egg-laying female syrphid flies prefer certain strata of vegetation but do not discriminate among plant species (Bastian 1986). Spiders spin their webs between structures, ants search everywhere, etc. Similarly, specific parasitoids are known to find their hosts by means of kairomones (Birch 1974) as much as by plant-specific cues. The

Chemical aspects of host-plant specificity in threeLarrea-feeding grasshoppers

The host-selection behavior of three species of grasshopper feeding on creosote bush,Larrea tridentata, in southern California was investigated. The species wereBootettix argentatus, which is monophagous;Ligurotettix coquilletti, oligophagous; andCibolacris parviceps, polyphagous. The monophagous species is stimulated to bite by nordihydroguaiaretic acid (NDGA), a compound that is characteristic of the host plant and that may comprise up to 10% of the dry weight of the leaf. Host specificity ofB. argentatus is enhanced by deterrent responses to compounds present in the surface waxes of all non-host-plant species. Both the oligophagous and polyphagous species are deterred by NDGA at naturally occurring concentrations. Their association withLarrea is probably based on tolerance of the plant chemicals rather than on dependence on specific chemicals. Factors other than the chemistry of the plant probably also contribute to the specificity ofB. argentatus andL. coquilletti.

VARIATION IN PREFERENCE AND SPECIFICITY IN MONOPHAGOUS AND OLIGOPHAGOUS SWALLOWTAIL BUTTERFLIES.

Although variation in oviposition preference and specificity for host plants has been demonstrated within populations of a variety of oligophagous insect species, it is unknown whether genetic variation in host choice is lost within populations of monophagous species. Analysis of a locally monophagous butterfly species, Papilio oregonius, and a locally oligophagous species, P. zelicaon, showed significant variation in oviposition preference within populations of both species. Females of both species chose primarily their native hosts. Nonetheless, the percentages of eggs laid by individual females among the plant species and the number of plant species on which individual females laid eggs differed significantly among isofemale strains within populations. Moreover, some females within all isofemale strains of both species laid a few eggs on Foeniculum vulgare, an umbelliferous species that does not occur in the native habitats of these populations but is a host for Papilio species in other geographic areas. The results suggest that local monophagy and oligophagy in these species reflect the relative ranking among potential plant species. Both populations harbor variation in oviposition choice that could allow for host shifts if these populations invaded new habitats.

Phytophagous Insect Faunas of the Native Thistles, Cirsium brevistylum, Cirsium congdonii, Cirsium occidentale, and Cirsium tioganum, in Southern California

Phytophagous insects representing four orders, seven families, and seven species compose the insect fauna of Cirsium brevistylum Cronquist (Asteraceae) in southern California. Similarly, phytophagous insects representing five, five, and five orders, 9, 18, and 16 families, and 13, 26, and 18 species are reported from Cirsium congdonii Moore and Frankton, Cirsium occidentale (Nuttall) Jepson, and Cirsium tioganum (Congdon) Petrak, respectively. Most insects feeding on these thistles are polyphagous, ectophagous, sap- and foliage-feeding species; however, one or two nearly monophagous and oligophagous species (i.e., only attacking Cirsium spp. and Carduineae, respectively) were found in or on each of the four thistles. Species packing in flower heads averaged 0.4, 0.3, 1.6, and 0.9 endophagous species per sample site (range, 0—4) for C. brevistylum, C. congdonii, C. occidentale , and C. tioganum , respectively. Species packing in or on shoots averaged 2.7 ± 1.2 (x ± SEM), 6.0 ± 1.4, 6.3 ± 3.2, and 10.3 ± 3.4 species per sample site, respectively. High proportions (65—86%) of the insect associates reported also reproduced on these native herbs.

Phytophagous Insect Faunas of the Two Most Common Native Cirsium Thistles, C. californicum and C. proteanum, in Southern California

Phytophagous insects representing six orders, 26 families, 49 genera, and 59 species are reported as composing the insect fauna of Cirsium californicum Gray (Asteraceae) in southern California. Similarly, phytophagous insects representing six orders, 20 families, 29 genera, and 31 species are reported from C. proteanum J. T. Howell. Most insects feeding on these thistles are polyphagous, ectophagous, sap- and foliage-feeding species. Ten (17%) of 58 species assessed for host specificity on C. californicum are stenophagous (i.e., their host plants restricted at least to Cynareae); 7 (23%) of 31 species on C. proteanum are stenophagous. The six oligophagous species (i.e., only attacking Carduinae) on C. californicum and four oligophagous species on C. proteanum include the flower head-infesting weevil Rhinocyllus conicus (Froelich), introduced and established for the biological control of alien, asteraceous thistles of European origin. Species packing within flower heads of both thistles averaged approximately two (range, 0–4) native insect species. Species packing in or on shoots of C. californicum averaged 10.5 ± 0.9 (⁠|$\bar x$| ± SEM) species; for C. proteanum, 8.4 ± 0.8 species.

Phytophagous Insect Fauna of Polygonum perfoliatum, an Asiatic Weed Recently Introduced to Pennsylvania

Insect surveys of a recent Asiatic adventive, Polygonum perfoliatum L. (Polygonaceae), were conducted in southcentral Pennsylvania during 1981 through 1983. The associated insects are listed, and the phenology and known host range of selected common species are discussed. The fauna, consisting of 34 species (5 orders, 15 families) that develop on the weed and 12 species that feed on Polygonum only as adults, is dominated by polyphagous, ectophagous sap- and foliage-feeding insects; only two oligophagous species associated with other polygonaceous plants were collected. Herbivory generally was casual, and several niches on P. perfoliatum remain unfilled. The fauna is compared with that of crownvetch ( Coronilla varia L.), an introduced legume of similar growth habit that occupies similar habitats in Pennsylvania.

Auchenorrhyncha‐host plant interactions: leafhoppers and grasses

ABSTRACT. Grass nutrient levels differed considerably between the grass species and with time. Most species of leafhopper (Homoptera, Auchenorrhyncha) were present on all the grasses sampled but each grass had a different dominant leaf‐hopper fauna. The leafhopper—plant association varied depending on the leafhopper species. Species that were strongly associated with one host were rare. Other more oligophagous species were associated with a particular nitrogen level in the grass. These species were found on grasses that had nitrogen concentrations within a narrow range. As the plant nitrogen levels altered (associated with flowering, seed setting, and senescence) leafhoppers switched onto other food plants that had a suitable nitrogen level. An intermediate group of leafhoppers showed little specificity and little association with plant nitrogen levels.

Odontota horni, 1 a Hispine Leaf Miner Adapted to Soybean Feeding in Illinois2

Larvae of Odontota horni Smith (Coleoptera: Chrysomelidae: Hispinae) produce a “blotch” type mine in soybean leaves. Adult females readily feed and oviposit on soybean in the laboratory and larvae complete development on this plant. O. horni is a native Leguminosaeassociated oligophagous species that has expanded its host-range to include soybean. Although the damage potential to soybean is remote, O. horni represents an interesting example of the adaptation of elements of a local fauna to an introduced crop plant.

POPULATION GENETIC CONSEQUENCES OF FEEDING HABITS IN SOME FOREST LEPIDOPTERA

BY SURVEYING VARIATION AT ALLOZYME LOCI IN SEVERAL PHYTOPHAGOUS LEPIDOPTERAN SPECIES (GEOMETRIDAE), WE HAVE TESTED TWO HYPOTHESES ABOUT THE RELATIONSHIP OF GENETIC VARIATION TO ENVIRONMENTAL HETEROGENEITY: (1) that allozyme polymorphisms may exist because of associations between genotypes and "niches" (different host plants, in this instance), and (2) that the overall genetic variation of a species is correlated with environmental heterogeneity (or breadth of the species' overall ecological niche).-Genetic differentiation among samples of oligophagous or polyphagous species taken from different host species was observed in one of three species, at only one of seven polymorphic loci. The data thus provide no evidence for pronounced genetic substructuring, or "host race" formation in these sexually reproducing species, although host plant-genotype associations in a parthenogenetic moth give evidence of the potential for diversifying selection.-In a comparison of allozyme variation in polyphagous ("generalized") and oligophagous ("specialized") species, heterozygosity appeared to be higher in specialized species, at all polymorphic loci but one. It is possible that this unexpected result arises from a functional relation between breadth of diet and genetic variation.

Sensory Activity and Food Intake: a Study of Input-Output Relationships in Two Phytophagous Insects

Sensory Activity and Food Intake: a Study of Input-Output Relationships in Two Phytophagous Insects