Larval Movement Research Articles

Larval Movement of the Range Caterpillar, Hemileuca oliviae (Lepidoptera: Saturniidae)

The movement behavior of the range caterpillar, Hemileuca oliviae Cockerell (Lepidoptera: Saturniidae), was studied at two sites 10 km south of Springer, N.Mex., in the summer of 1979. Hourly measurements of the distance and direction larvae traveled were made weekly from hatch to pupation. Larval movement was similar at the two sites. First instar larvae were generally stationary; instars II to IV traveled an average of 1 to 3 m each, instar V averaged 9 m, and instar VI averaged 20 m. Maximum larval movement occurred just before pupation. Maximum total movement for the entire larval period was less than 100 m, demonstrating that larval dispersal is not the major cause of range expansion. Direction of movement of all the instars was highly variable, and no distinct pattern was ascertained. Early instars moved most often in late afternoon (1400 to 1700 MST), whereas instars V and VI were most active at midmorning (0900 to 1100 MST) and just before sunset(1500 to 1800 MST). Larvae of all instars rarely moved at night.

The aquatic drift patterns of black flies (Diptera: Simuliidae)

Larval (5th-final instar) drift patterns of five species of black flies (Prosimulium mixtum, Stegopterna mutata, Simulium tuberosum FG, S. vittatum IIIL-1, and S. vittatum IS-7) were analyzed. The diel drift patterns were not species-specific, but consistently exhibited a marked increase after sunset, preceded by a period of minimal drift. The drift minimum generally occurred during or shortly after the period of maximum water temperature. Larvae showed significantly more nocturnal than diurnal drift. Pupal drift was attributed to accidental detachment from the substrate. Adult drift was over 90% diurnal and usually composed primarily of teneral individuals. Upstream larval movements of the S. vittatum and S. tuberosum complexes were each less than 6.5% of the total upstream and downstream larval movements. The proportion of parasitized larvae of the S. vittatum and S. tuberosum complexes was generally higher in the benthos than in the drift.

Bean Leaf Beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae): Physical Factors Affecting Larval Movement in Soil1

Bean leaf beetle larval movement in response to food and to soil moisture and texture (loamy sand, sandy clay loam, and organic) was studied in laboratory experiments. All larval instars of the bean leaf beetle have the capability for relatively large movements in the soil and will move from unfavorable to favorable food, texture, and moisture conditions. These studies suggest increased desiccation due to cuticle abrasion as one explanation for observed differences in survival among soils.

Developmental arrest of endoparasitoid wasp larvae (Nemeritis canescens grav.) caused by an ectoparasitoid wasp (Bracon hebetor say)

AbstractThe effect of Bracon hebetor‐induced host paralysis on the development of Nemeritis canescens was examined. These two wasp species were found to often coexist at the same location and can utilize the same host species. N. canescens females were allowed to oviposit into Anagasta kuehniella larvae. The parasitized host caterpillars were then exposed to B. hebetor females which paralyzed the caterpillars with a venom. Subsequent to host paralysis and removal of the B. hebetor females, host caterpillars were dissected daily to determine the developmental stage of the endoparasitoid N. canescens larvae. Virtually complete inhibition of development occurred when host paralysis was induced within 12 hours of N. canescens oviposition although larval movement and morphology were normal. Developmental inhibition also took place when host paralysis was induced 1 week after oviposition but it required a few days to become evident. The possible mechanisms of developmental arrest are discussed.

Chemotaxis of larval soybean cyst nematode,Heterodera glycines Race 3, to root leachates and ions

Second-stage larvae of the soybean cyst nematodeHeterodera glycines Race 3 were attracted in an in vitro bioassay to pooled leachates of soybean roots that were expressed as root gram-hours (1 g of root/hr/vol). Their responses were dosage dependent with maximal attraction to a 5 root g-hr/ml source. Optimal bioassay conditions used 24 hr for gradient formation and 1.5 hr for larval movement. Individual plants produced leachate with little variation in biological activity. Production was constant for five days of preparation. The attractive activity of root leachate declined with storage at 4 °C and heating over 30 °C, but loss of activity was reduced by freezing. Extraction and Sep-Pak fractionation indicated that the attractions(s) was water-soluble. Larvae were attracted also to several ionic solutions.

The Phenomenon of Egg Mass Liquefaction in Nemotaulius hostilis (Hagen) (Trichoptera:Limnophilidae)

Experiments were conducted to determine why gelatinous egg masses of the caddisfly Nemotaulius hostilis (Hagen) liquefy upon emergence of first instar larvae. Larvae did not feed on the polysaccharide matrix and thus, consumption did not cause its liquefaction. Destruction of portions of the matrix by various mechanical means, including the simulation of larval movement by small pins moving under the influence of an oscillating magnetic field, did not result in liquefaction. End-attacking enzymes apparently did not cause degradation of the matrix either. We hypothesize that enzymes which attack the central portions of the polysaccharide chains are involved.

Ecological investigations of the american dog tick,Dermacentor variabilis(say), in northwest Ohio (Acari: Ixodidae)

Abstract Ecological investigations on Dermacentor variabilis were conducted in both the laboratory and a metropark area in Lucas County, Ohio. Adult tick surveys were conducted in 1979 and 1980. Adults were collected most often during sunny days on the borders of coniferous woodlots. Adult activity began in late April and showed a bimodal distribution with peaks in April-May and August-September. Larval host-seeking behavior was studied. In the field, white-footed mice served as the primary host species. Larval movement over a seven day period was observed by releasing fluorescent, dust-marked larvae into woodlot habitats. In the laboratory, larvae displayed a more positive taxis to oak than pine litter. Oak leaf litter alone attracted more larvae than oak litter which contained rodent hair.

Sunflower Moth Larval Distribution in Sunflower Heads 1

The distribution and movement of sunflower moth, Homoeosoma electellum (Hulst), larvae in flowering sunflower heads was determined. Sampling was initiated 3 days after first bloom and was continued at 3-day intervals untill larval numbers substantially declined. Flowers were divided into eight sections and each section into five subsections before larvae were counted. Larval counts from adjacent eighth sections were combined to create quarters and halves. There were no statistical differences ( P < 0.05) In larval densities among eighth sections in 91% of the heads, quarter sections in 86% of the heads, and half sections in all heads sampled. Larval movement among subsections of a head was influenced by floret and seed maturation, and to a lesser degree by instar.

Behavioral Process of Aggregation of the Red-Striped Sawfly, Arge nigrinodosa MOTSCHULSKY (Hymenoptera : Argidae)

The larval behavior leading to aggregation was observed in the laboratory. Hatchlings just emerged from an egg mass moved toward the tip of a shoot irrespective of the direction of gravity, went into a petiole in turn, and colonized. The aggregation was rapidly formed by all the larvae having this fixed pattern of behavior on a shoot.The following three points were considered essential for the formation of aggregation. Firstly, the orientation of the ovipositing female orients the hatchlings to come out in the upward direction, i.e. in the direction of the tip of the shoot. Secondly, the larvae have the basic habit of moving straight-forward between petioles on a shoot. Thirdly, the direction of light and the direction of the petiole which makes an acute angle with the shoot were recognized as factors reponsible for the change of course in larval movement.

Field Evaluation of Foliar Insecticides Against Rice Caseworm, 1980

Abstract Fourteen days after transplanting, field plots(2 m2) were hand infested with greenhouse-reared second instar larvae at 4 larvae/hill. The next day insecticides were applied as foliar sprays at 0.75 kg ai/ha in a volume of 300 l/ha. The IRRI (Los Banos, Laguna, Philippines) trial (randomized complete block design) was replicated 4 times over time. Each plot surrounded with levees was encircled with plastic sheeting to prevent interplot larval movement. Two replications planted April 4 were sprayed April 18 and two replications planted May 26 were sprayed June 9. Climatic data for the two 10-day periods after each spraying were: rainfall 0 and 8.2mm, RH 79% and 83%, mean daily maximum temperature 32° and 32° C, and mean daily minimum temperature 23 and 25° C, respectively. Caseworm damage was scored immediately before spraying and 5 and 10 days later. A tiller was scored as damaged if at least one leaf was cut by caseworm feeding. The leaf scraping index (1-9) was based on percent leaf area removed: 1 = 0%, 3 = 1-10%, 5 = 11-25%, 7 = 26-50%, 9 = 51-100%.

European Corn Borer: A Nonpreference Mechanism of Leaf Feeding Resistance and Its Relationship to 1,4-Benzoxazin-3-One Concentration in Dent Corn Tissue12

A nonpreference mechanism of resistance, as indicated by larval movement off the host plant, plays an impor tant role in the resistance of dent corn, Zea mays L., to leaf feeding by Ostrinia nubilalis (Hübner). When compared with the other inbred lines, the high level of leaffeeding resistance found in the inbred line, CI31A, can be attributcd to its increased level of non preference. Whorl concentrations of 2-hydroxy-7-methoxy-2H.1, 4-benzoxazin-3 (4H) one (HMBOA) and 2,4-dihydroxy-7-methoxy-2H-I, 4-benzoxazin-3(4H)-one (DIMBOA) were significantly different between inbred lines. The data indicate that DIMBOA is a primary chemical factor in the expression of non preference.

Embryonic and Post-Embryonic Development of Cylindrocorpus Longis'Toma (Nematoda: Cylindrocorporidae)

Embryonic development in C. longistoma follows the general pattern of other nematode species. Embryonic development lasts 30-34 hours. The relationship between larval movement and the hatching mechanism is discussed. The proportional changes which occur in gross body form during postembryogenesis are studied through a biometrical analysis of morphometric and allometric characters. The greatest increase in body length occurs during the third stage, coinciding with the greatest increase in gonad length. Due to lack of allometry between pairs of morphometric characters, 'a', 'b', and 'c' ratios are unacceptable for taxonomic purposes pertaining to this species. Growth of the reproductive system is relatively stable and the use of 'V' and 'T' for taxonomic purposes is acceptable. The genital primordium of first- and second-stage larvae consists of two germinal and two somatic cells. Sexual differences are discernible during the second molt by the presence or absence of specialized ventral chord nuclei and differential development of the genital primordium. Specialized ventral chord nuclei take part in the formation of the vagina. A specialized somatic nucleus separates from the uterine wall and initiates the vaginal primordium. Specialized ventral chord nuclei are absent in male larvae. During the third molt the anterior portion of the male gonad turns posteriad and grows along the ventral side of the body. Primordia of spicules and gubernaculum begin development during the third molt and male accessory structures are completed during the final molt. Nuclear divisions in the reproductive system occur throughout molts and stages.

Behavioral development of the cockroach ( Periplaneta americana)

The 12 to 16 cockroach pharate first instar larvae ( Periplaneta americana) which inhabit a single ootheca simultaneously eclose and hatch after 30 days of incubation at 29°C. Descriptions of behavior development were obtained by observing larvae which were removed from the oötheca after 16 to 18 days and incubated individually in organ culture dishes. The first movements were localized muscle twitches and depressions of the soft cuticle which first appeared at approximately 16 days. Coordinated multisegmental flattening movements of the abdomen and wave movements which rippled through the entire body appeared by 20 to 22 days. The frequency of larval movements increased up to 26 to 27 days and then decreased until hatching around day 30. Up to 28 days, most larval movements were localized twitches. The proportion of coordinated multisegmental movements increased from 18 through 29 days when they became the most frequent type. Larvae were largely quiescent on days 29 to 30 when eclosion and hatching movements were spontaneously initiated. Eclosion and hatching are performed concurrently using the same caudal to rostral peristaltic wave movements. All of the 12 to 16 larvae occupying a given oötheca eclosed and hatched simultaneously. Ligation of various body regions indicated that neither the head nor thorax were necessary for the performance of the rhythmic eclosion-hatching movements of the abdomen once they are initiated. Also, larvae with mid-abdominal ligations maintained asynchronous eclosion waves on both sides of the ligation, indicating that a given abdominal ganglion is capable of organizing the patterned motor output within its own segment and that any abdominal ganglion is capable of triggering eclosion movements in the adjacent rostral segment. The eclosion-hatching movements of the pharate first instar larvae are immediately terminated when the cuticle is removed. The first instar larvae which emerge are miniatures of the adult and perform the typical adult locomotor gait.

Observations on the free larval stage of Glossina morsitans morsitans Westw. (Diptera, Glossinidae): the possibility of a larval pheromone

AbstractUnder simulated natural conditions the anal orifice of the larva of Glossina morsitans morsitans Westw. appears to open either at or soon after parturition. The larva burrows on average within two minutes of deposition; pupariation is completed 10–15 min later. Using methods that prevent burrowing and prolong the crawling period, certain larval movements were related to the pre-pupariation anal discharges and to the rapid spread of the fluid. Although the anus is not generally thought to be connected with the hind gut during the whole of larval life, the presence of uric acid in the discharges indicates that the fluid is a product of Malpighian tubule excretion. In a two-choice chamber in an incubator, flies larviposited significantly more often in the experimental pot if it contained a water- or ether-soluble extract of larval excretion in addition to any pupariating larvae. This points to the presence of a larval phero-mone which may attract gravid females to a breeding site.

Quantitative Aspects of Simulium virgatum Coq. and S. Species Life History in a Southern Oklahoma Stream1

Simulium virgatum and S . species A from a south central Oklahoma limestone stream were found to have larval instars with the greatest percent weight gains during the 4th and 5th instars. Changes in survival, density, and biomass coincided with larval movements from eclosion to feeding, and from feeding to pupation sites. Downstream drift probably accounted for most population attrition. Larval development took from 21 to 35 days and pupation lasted from 4 to 5 days during late summer.

Hookworm behaviour: Larval movement patterns after entering hosts

Larvae of the cat hookworm, Ancylostoma tubaeforme migrate from the skin to the lungs of both mice and cats. Experiments have examined changes in the basic movement patterns of infective larvae after as long as 5 days within host tissues. Similarly, morphological developments and changes in unbound neutral lipid were investigated. There were no changes in the larvae except for a fall in the concentrations of lipid. Furthermore, it was found that larvae which had successfully completed a migration from the skin of a mouse to its lungs could successfully complete a second migration. The evidence does not support the hypothesis that a distinct series of tissues cr physico-chemical barriers may be sequentially followed in the migration of hookworms in their hosts. The migration route is seen as a much more random, less purposeful series of events.

Integrated control of apple pests in New Zealand

For six generations, 5th‐instar larvae of the codling moth (Laspeyresia pomonella) which had finished feeding in apples were tagged externally with cobalt‐58 and released on ‘Delicious’ trees, where they sought cocooning sites. The larvae were released according to their natural distribution in fruit in the trees and on the ground. Most larvae left the fruit between 90 and 210 cm above the crotches of the trees, and their distribution on the leaders was aggregated.The distribution of cocoons formed by the tagged larvae revealed net larval movement after release. Most cocoons were formed under bark (19.9 %), in natural holes and depressions (17.9%), and around pruning scars (13.4%) and spurs (15.2%). Maximum cocoon densities occurred between 60 and 150 cm above the crotch and on the trunk. Only 3.8% of cocoons were formed on the ground and 21.6% on the trunk and basal 60 cm of the main leaders, compared with 74.7% above this level. The cocoons were aggregated on the leaders and within individual sites, and most larvae appeared to spin up on the leader on which they were released. More cocoons occupied sites facing south than north, and within the trunk area the number of cocoons increased towards the base.Larvae in cocoons under bark and in large holes died from disease more frequently than larvae in other sites. Bird predation, by the silvereye (Zosterops lateralis), was influenced by the distribution of cocoons; predation increased with the height of cocoons in the trees and with increasing exposure of the different site types. The birds fed on the cocooned larvae mainly from May to August.The larval and cocoon distributions are discussed in relation to other published distributions and to descriptions of codling moth cocooning behaviour. The responses of silvereyes to cocoon density and distribution are compared with those of other known bird predators of the codling moth.

Insecticide granule distribution and the control of Lycoriella auripila (Diptera: Lycoriidae) in mushroom casing material

SUMMARYIn laboratory tests the distribution of insecticide in peat–chalk mushroom casing greatly affected the number of adult sciarids which emerged from larvae placed in 50 g samples. Only thionazin markedly reduced emergences when granules were clumped in the centre of the sample of casing. The slope of dosage mortality data for clumped granule treatments was less steep than for mixtures and gave estimated LD95 values of 16300 and 26.8 ppm respectively. Thus, the number of adults which emerged when granules amounting to 6.4 mg of chlorfenvinphos were clumped was 65% of those emerging when only 0.4 mg a.i. was mixed into 50 g casing. However, adults did not emerge when 3.2 mg of the same insecticide was mixed throughout the sample. Increased doses did not, therefore, compensate for inadequate mixing.With 0.2–0.4 mg a.i. chlorfenvinphos mixed through the casing, about three times as many sciarids emerged with the intact granules than when pulverized granules were used. This showed the lack of mobility of this chemical in peat‐chalk mixtures and the need for it to be homogeneously incorporated in commercial casing. Pirimiphos‐ethyl, diazinon and thionazin also gave improved kills when mixed into the casing rather than clumped.A χ2 test of the mortality data suggested a non‐linear dosage‐mortality relationship for treatments amounting to half the dish. However, LD95 estimates of 37.5 and 62.2 ppm were obtained for mixed and quadrant treatments. Thus, when 3.2 mg chlorfenvinphos was mixed into only half of the volume of casing, the number of adults emerging was only 6% of that from untreated casing. However, larval movement was negligible in untreated casing and this appeared to limit the effectiveness of chlorfenvinphos and pirimiphos‐ethyl when they were not evenly distributed throughout the casing. With thionazin and diazinon, mobility of the insecticide appeared to compensate for uneven distribution.

Mechanism of Thermopositive Behavior in Larval Hookworms

The behavior of Ancylostoma tubaeforme (Zeder, 1800) larvae has been investigated in logarithmic thermal gradients of 20 C to 35 or 40 C over 1.5 cm. Larvae responded positively and when tracked in agar, the tracks were significantly straighter than those of the unstimulated controls. Tracks of larvae in the "2-heat experiment" showed a direct migration to the area between the heat sources and then a movement to either heat source, providing further evidence for a true thermotaxis. Distributional analyses have been developed as a rapid method for assaying tactic movements of nematodes when compared with "random walk" movements. The rate of movement of larvae responding up a steep gradient was more rapid than if warmed slowly at the same temperatures. Finally these results have prompted a hypothesis to explain the mechanism of thermopositive behavior of larvae of A. tubaeforme as a "behavioral overshoot," and the selective advantages are discussed. Among the conflicting reports of larval nematode orientation responses, the thermopositive movements of actively penetrating larvae of warm-blooded hosts have been considered one of the best substantiated (Payne, 1923; Wallace, 1961; Komiya and Yasuraska, 1966; Croll, 1970). Confusion and problems of interpretation still exist, however, because of the convection currents in some experimental designs, and the ambiquity between thermopositive and photopositive responses recorded using insufficiently cooled light sources (Parker and Haley, 1960). Surprisingly all reports of "thermotaxes" in nematodes have been based on distributional analyses following a period in a heat gradient. These designs have overlooked the possibility of aggregations occurring through kinetic changes in activity. Infective larvae have been tracked on agar and analyses of movement patterns attempted for Trichonema infective larvae (Croll, 1971) and for Ancylostoma tubaeforme (unpublished). From these and other tracks (Croll, 1969) it is known that arcs, caused by persistent asymmetrical biases in undulations, together with occasional reversal periods in which larvae move backwards for short distances, dominate larval movement patterns. The technique of accurately recording the movements of individuals is here applied to the behavior of A. tubaeforme larvae in thermal gradients. MATERIALS AND METHODS A. tubaeforme were cultured in moist cat feces at 30 C and tracked individually on 2% ion agar Received for publication 17 February 1972. (Croll, 1971). The conditions for tracking are so critical that we are confident that the water content of the agar, the nature of the surface film, and the texture of the surface were constant in each case. Larval movement patterns were also obtained by copying the positions of individuals on a grid which corresponded to one on the bottom of an agar-filled petri dish. Confidence can be placed on this technique, although it is less satisfactory than laboriously copying tracks inscribed in agar. Larvae were tracked at constant temperatures in Fisons' 50/G2 controlled-environment chambers, in 9-cm diameter agar plates held horizontally in the dark. When tracked individually larvae were removed at the end of the period. Because of idiosyncracies in larval movement patterns (Croll, 1971) and the tendency for individuals to follow a repeatable form of tracks, individuals which were tracked responding to thermal gradients were included in the "controls" which moved in nondirectional conditions. If the distribution of many larvae after a controlled period was examined, the plates were rapidly flamed over a Bunsen at the end of the experiments to kill the larvae without altering their distribution. A thermal gradient was maintained by placing a resistance wire in a glass tube into agar to a depth of 0.5 cm. The gradient on the agar surface was measured using a thermistor probe, until it was constant (about 20 min). All larval movements in gradients were observed in even, cooled, tungsten illumination of 5 to 10 c/ft2, passing perpendicularly to the larval movement, through the agar. Two heat sources were established by burying resistance wire in a "U tube" of 2 mm diameter, such that the heated elements passed upwards through the agar surface 2 cm apart. Those experiments testing distribution in directional light parallel to the agar surface used a "cooled" tungsten bulb of 100 c/ft2 intensity at th dge of the agar plate. The "straightness" of tracks has been quantified using: (1) tortuosity, or displacement/length, where displacement is the shortest distance between the start and end of the

Resistance in Soybeans to the Mexican Bean Beetle: II. Reactions of the Beetle to Resistant Plants1

Mexican bean beetles (Epilachna varivestis Mulsant) displayed differential preference reactions when fed foliage from resistant soybean (Glycine max (L.) Merrill) genotypes PI 229358, PI 227687, and PI 171451. These reactions included reduced longevity and fecundity in adults and weight loss and high mortality in larvae. These symptoms appeared similar to starvation and hypothetically resulted from reduced consumption of resistant foliage by the insects.Larvae tended to fall from plants of the genotypes PI 229358 and PI 171451 possibly because lack of feeding stimulants or presence of repellents caused high larval movement and leaf surfaces provided poor footing for the insects.