Labidomera Clivicollis Research Articles

Abundance of Herbivores on Six Milkweed Species in Illinois

To aid the understanding of the role of insect herbivores as selective agents in the evolution of their host plants a survey of herbivore abundance and impact was undertaken in central Illinois on the six milkweed species: Asclepias incarnata, A. sullivantii, A. syriaca, A. verticillata, A. amplexicaulis, and A. tuberosa. These species occur in this order on a moisture gradient from wet to dry soil conditions. This survey revealed that 12 species occurred at an abundance of at least one individual per 100 host stems in 1 plot-year on one host species: Oncopeltus fasciatus*, Lygaeus kalmii*, Aphis nerii*, Labidomera clivicollis*, Tetraopes tetrophthalmus*, T. femoratus, T. quinquemaculatus, Rhyssomatus, lineaticollis*, Danaus PlexipPus, Cycnia tenera*, Euchaetias egle and a leafminer. All but L. kalmii are specific to milkweeds in Illinois. Seven of these species, marked with asterisks, were abundant enough to act as major selective forces on the life history patterns of the milkweed species, populations and clones concerned. Results support the hypothesis that major differences in herbivore species and abundance on milkweeds are largely a result of (1) differences in the environments that milkweeds successfully colonize and (2) morphological (allocational) differences between milkweeds. This hypothesis related to differences in herbivores between milkweed species, populations within a species and clones within a population. The herbivores were very patchily distributed on milkweed species; and, of all the possible herbivore-host plant relationships, in only 17% of the pair-wise comparisons in the 12 x 6 matrix were herbivores abundant on host plants. When all plot-years and all pair-wise comparisons were considered, in only 10% of the 252 possible situations in the 12 x 21 matrix were herbivores abundant on host plants. Such patchiness of herbivores supports recent theory on plant defense strategies, which argues that early successional plants, such as the milkweeds studied, are hard to find by specialized herbivores.

Population Dynamics of a Relatively Rare Species of Milkweed Beetle (Labidomera)

Labidomera clivicollis (Coleoptera: Chrysomelidae, Doryphorini), the milkweed leaf beetle, is relatively rare in New York State, although one of its host plants (Asclepias syriaca) is abundant. A related species, Leptinotarsa decemlineata, is an economic pest of potatoes. A comparison of the population dynamics of Labiodomera with previously published information on L. decemlineata suggests that the major differing factor controlling the two species' relative abundance is the intensity of predation to which the larvae are exposed. Predation on the young Labidomera larvae on the foliage of the host plants was the most important mortality factor in field experiments. Newly hatched beetle larvae were placed on 16 A. syriaca plants under natural conditions, in one of four treatment: (1) cage over the plant, with an open bottom; (2) sticky—trap barrier and groundcloth around the plant's base; (3) both barrier around base and cage over plant; and (4) control plants. The mortality could then be separated into four components: abiotic mortality, ground—dispersed predation, air—dispersed, and spider predation—plus—cannibalism. The rate of larval mortality on the control plants was high, averaging 35% per day; all of the 112 control larvae (on four plants) died by day 12 of the experiment. Ground—dispersed predation alone accounted for 54% of the total mortality. Important predators included Nabidae, Pentatomidae and Syrphidae (larvae); they were generalized, not specialized, arthropod predators. Another field experiment investigated the effect of different clutch sizes on larval mortality rates, with and without sticky barriers. The protective effect of the barriers, and hence the important of ground—dispersed predators, was confirmed in the second experiment. These results suggest that the beetle's preference for swamp milkweed for oviposition may be adaptive to avoid ground—dispersed predation. Swamp milkweeds frequently grow in marsh habitats with water around the base of the plants. Larvae on these plants would be protected by a "moat effect." A review of the literature on field experiments with Leptinotarsa suggests that an analogous "bare ground effect" protects the larvae on cultivated potatoes from effective predation.

A NEW SPECIES OF CHRYSOMELOBIA (ACARI: TARSONEMINA; PODAPOLIPIDAE) FROM NORTH AMERICA AND THE TAXONOMIC POSITION OF THE GENUS

AbstractThe larva, adult female, and adult male of Chrysomelobia labidomerae n. sp. are described. The adult female is compared with that of the only other described species in the genus, C. mahunkai from Europe. Chrysomelobia labidomerae is a parasite of adult milkweed leaf beetles, Labidomera clivicollis (Coleoptera: Chrysomelidae), in North America. Morphological similarities of all stages of Chrysomelobia with those of the generalized podapolipid Dorsipes support the retention of Chrysomelobia in the Podapolipidae as a most primitive genus in that family and the only one with 4 pairs of legs in the adult female.

DEVELOPMENT AND BIONOMICS OF CHRYSOMELOBIA LABIDOMERAE (ACARI: TARSONEMINA; PODAPOLIPIDAE), A PARASITE OF THE MILKWEED LEAF BEETLE (COLEOPTERA: CHRYSOMELIDAE)

AbstractAdult females of Chrysomelobia labidomerae Eickwort lay eggs on the upper surfaces of the hind wings of Labidomera clivicollis (Kirby). The eggs hatch in approximately 7 days and male and female larvae feed at the base of the wings and in the meso–metathoracic crevice and swell to about twice their original length. For about the second half of the approximately 7-day larval stadium, the larvae are inactive (pharate adults) and are usually cemented to the undersurfaces of the elytra. Inactive female larvae are accompanied by adult males that apparently copulate with the newly emerged adult females. The pharate adult is enclosed in a cuticular sac that may represent a calyptostatic nymphal instar. Adult females feed on the beetle’s abdominal terga and sometimes also occur on its venter where they do not feed. Females disperse from host to host when the beetles copulate. The species is arrhenotokous. Mites overwinter on the diapausing adult beetles and do not infest the immature stages of their host. Even at high population levels, the mites do not noticeably affect the longevity or fecundity of their hosts.

Studies on D‐alanine in the Heteroptera*

ABSTRACTFour milkweed associated insects were assayed for free D‐alanine by gas‐liquid chromatographic methods. Oncopeltus fasciatus and Lygaeus kalmii, reared aseptically on milkweed seeds, showed high titres of free D‐alanine. Labidomera clivicollis showed traces of the D‐isomer whereas none could be detected in Tetraopes tetrophthalmus. O.fasciatus reared aseptically on sunflower seed showed high titres of D‐alanine. No D‐alanine could be detected in milkweed seed hydrolysates. Several museum specimens of the orders Hemiptera and Homoptera were assayed and all showed high titres of D‐alanine.

Cannibalism and Kin Selection in Labidomera clivicollis (Coleoptera: Chrysomelidae)

Cannibalism and Kin Selection in Labidomera clivicollis (Coleoptera: Chrysomelidae)