Host Plant Stem Research Articles

A simple definition of food resources for the highly polyphagous Lygus lineolaris (Hemiptera: Miridae) enables prediction of adult abundance.

Lygus lineolaris (Palisot de Beauvois) is a highly polyphagous herbivore with more than 300 known host plants. The high polyphagy has created logistical challenges for understanding its population dynamics. I hypothesized that the primary food resource of this species can be characterized simply, cutting across the multiple host plant species, and enabling a simpler understanding of its population dynamics. The food resource was defined as the apical buds and meristematic tissue and terminal flowers and young seeds. Adult abundance in a habitat was related to the relative abundance of food in the habitat, abundance on a host plant stem was related to the amount of food resource on the stem, and the rate of emigration was lower from host plant patches with higher amounts of food resources. These results suggest that the population dynamics of L. lineolaris depends less on the identity of the host plants and more on the amount of food resource the various host plant species provide.

Diversity and abundance of lepidopteran stem borers and their host plants in Ethiopia

AbstractLepidopteran stem borers are among the most important insect pests of maize, sorghum and sugarcane in sub‐Saharan Africa. Except for Chilo partellus, the other stem borer pests in Ethiopia are indigenous to Africa and are assumed to have coevolved with some native grasses and sedges in the natural habitat. In addition to pest species, natural habitats harbour diverse non‐economic stem borer species, some of which are new to science. However, with the growing threats to natural habitats, some non‐economic stem borer species may switch or expand their host ranges to include cultivated crops and evolve as “new” pests. Besides host switch, some of the unknown species currently limited to natural habitats may disappear. We examined the diversity, abundance and interactions of lepidopteran stem borers and their wild host plants in five different vegetation mosaics in Ethiopia. The stem borer species diversity varied among vegetation mosaics and host plants. Forty‐four stem borer species belonging to 14 different genera in the families of Noctuidae, Crambidae, Pyralidae and Tortricidae were recorded from 34 wild host plants and through light trap. Among these families, Noctuidae was the highest in species richness in which 31 species were identified, out of which 15 species and two genera were new to science. This paper discusses the ecological interpretation of host plant–stem borer species interactions, particularly in relation to habitat disturbances.

Biology and morphology of immature stages of Lixus canescens (Coleoptera: Curculionidae: Lixinae).

Mature larvae and pupae of Lixus (Eulixus) canescens Steven, 1829 (Curculionidae: Lixinae: Lixini) are described and compared with known larvae and pupae of other Lixus species. The biology of the species was studied in Ukraine. A species of Crambe (Brassicaceae) was identified as host plant of both larvae and adults of this weevil. The weevil is very likely oligophagous. Lixus canescens prefers dry, sunny places, such as open areas of sand close to sea shores with growing host plants. Overwintering beetles emerge in the late spring (mid-May), and then feed and mate on the host plants. The highest level of activity of the adults was observed at the end of May. Larvae are endophagous in the host plant stem. At the end of July, the larvae pupate within the stem inside a pupation cell. Adults leave the cells at the end of summer and do not hibernate on the host plants. They then, most likely, spend some time feeding on the host plants and looking for suitable shelter in which to overwinter.

Larval cryptic coloration and mistletoe use in the metalmark butterflyDachetola azora(Lepidoptera: Riodinidae)

The last instar larva and pupa of the metalmark butterfly Dachetola azora (Godart) (Lepidoptera: Riodinidae) are described and illustrated for the first time. Mature larvae feed at night on leaves of the mistletoe Struthanthus sp. (Loranthaceae), remaining hidden during the day on the bark of the host plant stem, where pupation occurs. Morphological and behavioral traits here described are compared with those known for other putatively related genera in Riodinini.

Collective signals in treehopper broods provide predator localization cues to the defending mother

Many animal groups respond collectively to environmental cues. To understand the function of collective behaviour, an important first step is to establish how it varies in response to differences in the relevant cues. Because collective action arises from individual decisions, this in turn requires characterizing the behaviour of individual group members. In the treehopper Umbonia crassicornis, offspring live in cylindrical aggregations along a host plant stem. In the presence of a predator, offspring produce synchronized vibrational signals that elicit maternal defence. Predators typically attack the ends of the aggregation; because the mother must approach the predator to defend her offspring, we hypothesized that variation in collective signals reveals not only the predator’s presence, but also its location. The defending mother also produces signals, and we hypothesized that maternal cues influence the signalling behaviour of the brood. We simulated predation at either end of the aggregation. In the presence of the mother, (1) offspring closer to the predator were more likely to signal and (2) more offspring contributed to the group signals when the predator attacked the aggregation at the far end from the mother. Differences in group signals, emerging from position-dependent differences in signalling probability of individual offspring, could be used by the defending mother to determine the end of the aggregation being attacked. A loss of these signalling patterns in the absence of the mother reveals that maternal cues are necessary for the establishment of a reliable relationship between collective signalling and predator location.

Life history and larval morphology of Eurhinus magnificus Gyllenhal (Coleoptera: Curculionidae), a new weevil to the United States

Eurhinus magnificus Gyllenhal has been collected in south Florida, presumably introduced through trade with countries in its native range. Very little information has been published on the biology or taxonomy of this insect. We conducted studies to investigate various aspects of its life history and host plant associations. The pre-imaginal life stages of E. magnificus are described for the first time. Dimensions of the adult, egg, larval, and pupal stages are also provided; head capsule measurement revealed five larval instars. All life stages of E. magnificus were collected at several sites in Broward and Miami-Dade counties from the host plant Cissus verticillata (L.) Nicolson & Jarvis (Vitaceae). Eggs were laid singly within the succulent, young subterminal portion of the host plant stem, one or two occurring between two nodes. Gall formation was apparent by the first to third instar and continued to increase in size until pupation which occurred within the gall. Predators and pathogens appeared to be responsible for considerable mortality in the field; there was no evidence of parasitism of any of the life stages. Greenhouse studies were undertaken to determine E. magnificus development time and host specificity. Adult weevils attacked grape cultivars (Vitis spp.) and feeding opened the stems to fungal agents but no physical evidence of larval development was apparent on grapes.

Influence of Multiple Factors on Insect Colonization of Heterogeneous Landscapes: A Review and Case Study with Periodical Cicadas (Homoptera: Cicadidae)

The literature on herbivorous insects in heterogeneous habitats has addressed insect population responses to patch size, distance from source populations, habitat edges, and variation in host stem density. Studies typically conclude that insect colonists respond positively to the area of host plant patches, but there is little consensus on how insects respond to variation in host density at the patch level. Although observed variation likely results partially from differences in study species and focal habitats, deviations from expectations also may reflect the importance of unmeasured habitat parameters. In this study of colonization by cicada Magicicada cassinii (Fisher) in an experimentally fragmented old field, we simultaneously examined landscape variation in patch size, distance from the sources of colonization, and local host plant stem density (at a within-patch scale) and also considered edge effects. Per stem colonization was positively related to proximity to the population source and habitat patch size but negatively related to local host stem density. The effect of edge was nonsignificant. When coarser scale estimates of local stem density (calculated by averaging the figures for all quadrats within patches) were used in analyses, fewer significant main effects were found and sometimes interactions occurred. Our study highlights the importance of including all potential explanatory variables in analyses, with what we feel is a novel observation that the explicit consideration of fine-scale, within-patch variation in local stem density can be important to the interpretation of insect dispersal and colonization.

Arboreal ants build traps to capture prey

To meet their need for nitrogen in the restricted foraging environment provided by their host plants, some arboreal ants deploy group ambush tactics in order to capture flying and jumping prey that might otherwise escape. Here we show that the ant Allomerus decemarticulatus uses hair from the host plant's stem, which it cuts and binds together with a purpose-grown fungal mycelium, to build a spongy 'galleried' platform for trapping much larger insects. Ants beneath the platform reach through the holes and immobilize the prey, which is then stretched, transported and carved up by a swarm of nestmates. To our knowledge, the collective creation of a trap as a predatory strategy has not been described before in ants.

Endophagous insects and structural niches on plants: ecology and evolutionary consequences

Summary1. The endophagous weevil Lixus elongatus was studied on two Carduus species in order to look for the impact of a structural gradient in host plant stem diameter on the life cycle and the genetic structure of this species.2. Body size of L. elongatus females was correlated positively with their fecundity and the stem diameter at the location of oviposition.3. Emerging individuals showed a significantly positive relationship of body size with the stem diameter at their pupation and emergence site. Mating behaviour was positively size‐assortative.4. Allozyme analyses indicated a gradient of genetic differentiation along body size classes and a decreasing heterozygosity with decreasing body size.5. The results led to the conclusion that a structural gradient in plants can promote body size variability in an endophagous herbivore through phenotypic constraints of the host plant and the herbivore. As size‐assortative mating translates this variability into differential gene flow between individuals of different body size, this could provide the raw material for speciation processes. Within a single host plant patch, however, further processes are necessary to split the existing genetic gradient into separate gene pools.

INFLUENCE OF SOIL SURFACE CONDITIONS AND HOST PLANT ON SOYBEAN NODULE FLY RIVELLIA QUARDIFASCIATA (MACQUART) (DIPTERA: PLATYSTOMATIDAE) OVIPOSITION1

Soybean nodule fly, Rivellia quadrifasciata (Macquart) eggs were oviposition in the soil and crop residue around the bases of potential larval host plants. Approximately 75% of the egg clutches observed being oviposited in cracks and crevices, in the field, were within 2 cm of the host plant stem (Phaseolus limensis Macf. L.). Most eggs were oviposited within 2 mm of the soil surface but eggs were sometimes deeper when females entered soil cracks and crevices. Oviposition from laboratory colony adults was not observed in the absence of host plants in no-chioce situations. When given a choice between closely arranged pots of soil with and without soybean plants, little oviposition occurred in soil without plants. Significantly (p = > 0.05) more oviposition occurred in pots containing soybean plants with loose soil than with compacted soil surfaces. The short-term responses of females to the absence of appropriate oviposition sites included egg retention and apparent increased flight activity.

Studies on the mating system of the winter cherry bug, Acanthocoris sordidus Thunberg (Heteroptera: Coreidae) II. Harem defence polygyny

SummaryThe mating system of the winter cherry bug, Acanthocoris sordidus, was analyzed precisely. As a result, it was found that male adults of this species establish a small territory for mating on the stem of host plant which harbors females. These males abandoned their territories soon after the disappearance of monopolized females. Thus it was confirned that the cue for the territorial establishment of males is the presence of females per se on the host plant. Moreover, most aggregations of adults observed on the host plant contained only a single male. This one‐male unit in the mating was named a harem. Harem holding males were usually big in body‐size and had a high chance of copulations. The defence behaviors of harem holding males, the mating disparity among males, and the oviposition habit of females in relation to the mating system, were observed. The results obtained were discussed in relation to the sexual selection theories.

The Natural Mortality of Erioischia brassicae (Bouche) (Diptera, Anthomyiidae) During the Egg Stage of the First Generation

(With 4 Figures in the Text) In an earlier paper (Hughes & Salter 1959) evidence was given of the primary importance of the egg mortalities in the natural control of the first generation populations of Erioischia brassicae. Detailed studies of these mortalities were impossible because of the limitations of the technique for estimating the total number of eggs laid in the soil around the host plants. With this method the soil within 5 cm of the host plant stem was removed to a depth of 2 cm and replaced with fresh soil to bring the area back to normal. The fresh soil was exposed to oviposition by E. brassicae for a standard period, and then the soil was removed again and the eggs present in it were counted after separation from the soil by flotation in water. The number of eggs counted was assumed to be the number laid during the period of exposure and the total of a series of consecutive counts made throughout the oviposition period was taken as the total number of eggs laid. The demonstration of substantial daily egg losses caused by predation (Wishart, Doane & Maybee 1956) showed that egg counts made after a few days' exposure of fresh soil around the host plants would record the number of eggs laid during that period less the number eaten by predators. In other words, if predation were taking place, egg counts made in this way would always underestimate the total number of eggs laid. Later in this paper a description will be given of a modification of Wishart's technique for demonstrating egg losses, which has been used at Wellesbourne, and has again confirmed the existence of substantial egg losses. Since egg losses have been shown to be considerable it has become clear that egg counts made after the same time interval are only directly comparable if the level of predation is similar. Egg counts made after different time intervals can only be directly compared if there is no appreciable significant predation. To avoid the consequences of this experimental error, day by day estimates of the egg loss are required so that the actual number of eggs laid can be calculated from the number counted.