Larvae In Galls Research Articles

Prvi nalaz parazitoda (Platygaster robiniae) na bagremovoj muhi šiškarici u Bosni i Hercegovini

Acacia is an allochthonous tree species that has been introduced into our region 400 years ago. Although the invasive species of Obolodiplosis robiniae in this region was first determined in 2007, significant damages have not been recorded on the acacia trees. Average number of galls on black locust leaflet were from 1,04 to 1,48. Average number of larvae in galls were from 0,42 to 0,77. In June of 2018, the first record of a parasitoid of black locust gall midge (Platygaster robiniae) was determined, although it is likely that was occured earlier, but this is the first record and represents a new species in the entomological complex in the territory of Bosnia and Herzegovina. Parasitism of larvae of Obolodiplosis robiniae were from 6,66 to 14,28% on different localities.

Bionomie a cecidogeneze Contarinia petioli (Kieffer) (Diptera, Cecidomyiidae)

Recently, the abundant occurrence of galls of Contarinia petioli (Kieffer) was noted on Populus tremula in the Brno region and elsewhere in southern Moravia. The bionomics and cecidogenesis of the gall midge was studied on 5 to 15-year-old aspens in Forest District Bílovice nad Svitavou, Training Fo­rest Enterprise Masaryk Forest in Křtiny in 2007 and 2008. Imagoes fly there at the end of April and at the beginning of May. Females lay eggs in several partial clutches at 1 to 6(10) pieces. About 91% newly hatched larvae settle on petioles of unfolding leaves, about 8% on the bark of terminal parts of shoots and about 1% on leaf blades. By means of sucking the larvae of the 1st and 2nd instars galls are crea­ted in the 1st half of May. Larvae of the 3rd instar occur in galls from the 20th May when galls are grown-up. Larvae abandon the galls in the 1st decade of June through an oval hole 0.6 × 0.4 mm in diameter. Galls are on average 6 mm long, 5.4 mm wide and 5.1 mm high. If they are localized within a short distance of each other then often create formations up to 17 × 11 × 9 mm in size. There are 1 to 6(10) chambers in galls and in each of them, only one larva develops. The paper deals in detail with the differentiation of galls including chambers as well as natural enemies of the gall midge. Torymus quercinus Boh., T. cultrans Graham & Gijswijt (Torymidae) and Tetrastichus sp. (Eulophidae) rank among natural enemies of larvae in galls.1

Benefits of photosynthesis for insects in galls

Insect-induced plant galls are predominantly reputed to act as strong carbon sinks, although many types of galls contain chlorophyll and have the potential to photosynthesize. We investigated whether the photosynthetic capacity of bud galls induced by a Pteromalid wasp, Trichilogaster acaciaelongifoliae, in Acacia longifolia subsidises carbon budgets or provides O(2) to the larvae while concurrently consuming CO(2) in the dense gall tissue, thereby maintaining (O(2)) and (CO(2)) within the range of larval tolerance. Low (O(2)) (<5%v/v) were found within the internal tissues of galls, and these concentrations responded only marginally to light, suggesting that the photosynthetic activity within the gall is inconsequential in the provision of O(2) to the larvae. The metabolic response of larvae to reduced (O(2)) and elevated (CO(2)) indicated that larvae were tolerant of hypoxia/hypercarbia and also capable of reducing their respiratory rates to cope with hypercarbia. The low mortality of larvae in galls shaded with Al-foil for 20days showed that photosynthesis was not vital for the survival of the larvae, although growth of shaded galls was substantially reduced. Gas exchange measurements confirmed that, while photosynthesis never fully compensated for the respiratory costs of galls, it contributed substantially to the maintenance and growth, especially of young galls, reducing their impact as carbon sinks on the host. We conclude that, although photosynthesis may contribute to O(2) provision, its main role is to reduce the dependence of the insect-induced gall on the host plant for photosynthates, thereby reducing intra-plant, inter-gall competition and enhancing the probability that each gall will reach maturity.

Larval distributions of the ectoparasitoid wasp Eurytoma robusta relative to the host tephritid gall fly Urophora cardui

AbstractParasitism may explain the patchy distributions of host populations. The present paper is a study of larval distributions of the parasitoid Eurytoma robusta in galls of the tephritid gall fly Urophora cardui. It focuses on E. robusta's choice of U. cardui gall and whether this changes relative to the rate of parasitism. Oviposition patterns were inferred by direct counts of larvae in galls and genetically, for both species, using indirect relatedness estimates between gall‐members. Furthermore, rates of parasitism in four populations were monitored for 4 years. The modal distribution of E. robusta larvae per gall was one and independent of the level of parasitism. The mean number of E. robusta per gall did not differ from Poisson distributions at different parasitism rates. We were not able to demonstrate a parasitoid preference for gall size. In contrast, parasitoids may have a negative effect on gall growth. Relatedness estimates showed that E. robusta gall members were often unrelated, whereas U. cardui were siblings. Thus, larval distributions of E. robusta suggest that oviposition behaviour is generally constrained and density independent. In four populations monitored over 4 years, parasitism was initially high (up to 70%), but suddenly declined with no apparent effect on fly (gall) abundance.

Effects of the gregariousness of larvae in galls on the reproductive success of the pine needle gall midge, Thecodiplosis japonensis Uchida et Inouye (Dipt., Cecidomyiidae)

AbstractThe effects of the gregariousness of larvae of the pine needle gall midge, Thecodiplosis japonensis Uchida et Inouye (Dipt., Cecidomyiidae), on the reproductive success of the midge were examined by field observations and laboratory experiments. The gregariousness of larvae in a gall did not cause the death of larvae in the gall, and the number of emerged adults per gall was expected to increase with the number of larvae per gall. Gregariousness decreased the size of larvae in galls. The decline in the larval size did not cause a simple decline in the number of eggs deposited per female. Females that emerged from medium size larvae deposited many more eggs than those from large and small larvae. The calculated number of eggs deposited per gall increased with an increase in the number of larvae per gall from one to five, but not when the number of larvae per gall was more than six. A simple model showed that if a female deposited about 10 eggs per egg cluster the number of eggs deposited by her daughters in the next generation would be maximum. The oviposition pattern and the gregariousness of larvae in galls in the field probably offer the midge the maximum reproductive success.

Life History and Parasites of Asphondylia borrichiae (Diptera: Cecidomyiidae), a Gall Maker on Borrichia frutescens

We studied the life history, seasonal and spatial abundance, and parasites of Asphondylia borrichiae Rossi and Strong (Diptera: Cecidomyiidae), a newly described gall maker on sea oxeye daisy, Borrichia frutescens (L.) DC. Galls are located on the apical meristem of the host plant, are usually solitary, often prevent flowering, and can kill the host stem. Individual galls may contain from one to eight fly larvae, most commonly one to three. Gall size is greatest in spring. Galls can be found year round, and there are several generations, of which the largest occurs in the summer. Gall densities differ consistently between sites, but the seasonal variation of galls within sites is very similar. Fly larvae in galls are attacked by four species of Hymenoptera, Rileya cecidomyiae and Tenuipetiolus teredon (Eurytomidae), Torymus umbilicatus (Torymidae), and Galeopsomyia haemon (Eulophidae), of which G. haemon causes the most mortality. At least two of the parasites are facultatively hyperparasitic. Parasitism levels are low in the spring but rise quickly to reach 100% in the early summer and late fall.

Susceptibility of first and second instar larvae of the spruce budmoth, Zeiraphera canadensis (Lepidoptera: Tortricidae), to the entomogenous nematode Heterorhabditis heliothidis under controlled conditions

The gallfly Eurosta solidaginis overwinters as freeze-tolerant, third-instar larvae in galls on goldenrod (Solidago canadensis). The mean crystallisation temperatures of different samples of larvae collected in February 1988 were between −8.6 and −9.3°C. The mean crystallisation temperature of haemolymph extracted from the same groups of larvae was on average 7–10° lower at −18°C. Dilution of haemolymph to 106 had no effect on the crystallisation temperature. Unlike many freeze-tolerant insects the nucleator which induces freezing in the larva at −9°C does not appear to be in the haemolymph. Haemolymph extracted from unwashed larvae froze at a significantly higher temperature compared to that obtained from larvae which had been washed to remove the frass (faecal matter) which adheres to the larval cuticle. A film of surface moisture placed around the larvae froze at −6 to −7°C and raised the crystal-lisation temperature of the larvae to −3°C following ice penetration through cuticular apertures, but did not affect the ability of larvae to pupate or the success of adult emergence compared to larvae which were cooled dry and a control group. Suspensions of 10 and 1% frass in 0.9% saline froze at elevated temperatures similar to the crystallisation temperature of the larvae. Maintenance of galls containing larvae at 0 and 10°C for up to 10 days had no effect on the crystallisation temperature of the larvae. At 25°C some larvae supercooled to below −22°C after only 2 days, whereas other larvae at the same temperature were still freezing at −9°C after 8 days. Loss of nucleator activity in E. solidaginis is apparently closely related to the internal reorganisation of the larvae immediately prior to pupariation.

Nucleators and sites of nucleation in the freeze tolerant larvae of the gallfly Eurosta solidaginis (Fitch)

The gallfly Eurosta solidaginis overwinters as freeze-tolerant, third-instar larvae in galls on goldenrod ( Solidago canadensis). The mean crystallisation temperatures of different samples of larvae collected in February 1988 were between −8.6 and −9.3°C. The mean crystallisation temperature of haemolymph extracted from the same groups of larvae was on average 7–10° lower at −18°C. Dilution of haemolymph to 10 6 had no effect on the crystallisation temperature. Unlike many freeze-tolerant insects the nucleator which induces freezing in the larva at −9°C does not appear to be in the haemolymph. Haemolymph extracted from unwashed larvae froze at a significantly higher temperature compared to that obtained from larvae which had been washed to remove the frass (faecal matter) which adheres to the larval cuticle. A film of surface moisture placed around the larvae froze at −6 to −7°C and raised the crystal-lisation temperature of the larvae to −3°C following ice penetration through cuticular apertures, but did not affect the ability of larvae to pupate or the success of adult emergence compared to larvae which were cooled dry and a control group. Suspensions of 10 and 1% frass in 0.9% saline froze at elevated temperatures similar to the crystallisation temperature of the larvae. Maintenance of galls containing larvae at 0 and 10°C for up to 10 days had no effect on the crystallisation temperature of the larvae. At 25°C some larvae supercooled to below −22°C after only 2 days, whereas other larvae at the same temperature were still freezing at −9°C after 8 days. Loss of nucleator activity in E. solidaginis is apparently closely related to the internal reorganisation of the larvae immediately prior to pupariation.

Why does the bud-galling sawfly, Euura mucronata, attack long shoots?

The bud-galling sawfly, Euura mucronata, attacked longer shoot length classes on its host, Salix cinerea, more frequently than shorter shoots. Shoot length accounted for 76 to 93 percent of the variance in number of galls per 100 shoots in three habitats: forest, watermeadow, and lakeside. The reasons for this pattern were addressed with studies on shoot length in relation to: 1. Number of resources (buds) per shoot; 2. Success in establishment of larvae in galls; 3. Gall size and resources per gall; and 4. Survival of larvae after establishment as influenced by plant resistance and natural enemy attack. The most important factors proved to be success in establishment of larvae, with percent of variance accounted for ranging from 57 to 77 percent in three of four sites where relationships were significant, and survival after establishment of larvae, with variance accounted for ranging from 40 to 54 percent in the same three sites. The pattern of survival was dictated by plant resistance and not by natural enemies. These two additive factors resulted in a general relationship across all sites of increasing emergence of fully developed larvae per cohort as shoot length increased, accounting for 78 percent of the variance. These adaptive advantages to attacking longer shoots are sufficient to account for the pattern of increased probability of shoots being attacked as they increase in length.

Studies on the distribution pattern of the pine needle gall midge, Thecodiplosis japonensisUchida etInouye (Diptera: Cecidomyiidae) in a pine forest

SummaryNumerical changes and distribution patterns of the pine needle gall midge, Thecodiplosis japonensisUchida etInouye, were studied during the period from 1978 to 1979 in a young plantation of Pinus thunbergii in Shiga Prefecture, Japan. The survivorship curve of this species was characterized by a low mortality of larvae in galls and two high mortalities before the formation of galls and during the overwintering period in soil.The within and between‐trees distributions of eggs and larvae in galls were examined by using the regression method. The egg distribution per shoot was aggregative both within and between host plants. The within‐tree variations in numbers of eggs per shoot were related to the differences in the abundance of available needles for oviposition per shoot among the canopy layers. The between‐tree variations reflected the heterogeneous emergence of adult females in the study plot. The degree of aggregation increased from egg to gall stage in both within‐ and between‐tree distributions and the increase was explained by the different mortality of larvae within trees and the inversely density‐dependent mortality between trees.The distribution patterns in the soil habitat stages were examined by the patchness index (). This species showed aggregative distributions in soil stages. There was a correlation in spatial patterns of adult emergence between the successive generations.The distribution properties of this species were discussed in connection with the population dynamics and the availability of host plants in the study plot.

The Barley Jointworm, Harmolita hordei (Harr.) (Hymenoptera: Chalcidoidea), in Prince Edward Island

AbstractThe barley jointworm, Harmolita hordei (Harr.), was first discovered at a point in the northeastern part of Prince Edward Island in 1946. It spread quite rapidly along the northern coastline of the province and more slowly southward, and today infestations may be found in most areas of the province. Inland movement of the pest did not start until about 1955 and since that time infestations have generally been lighter than they were previously.H. hordei overwinters as mature larvae in galls in barley stubble left in fields after the grain is harvested. Adults emerge the following year during late June and early July and oviposit in the stems of young barley plants, usually when the plants are six to eight inches high. Eggs are almost always laid just above the lower nodes or joints, either on the main or on tillering stems. The adults live for four to eight days. The larvae develop inside the stems and the plant tissue around them develops into hard, woody galls. The larvae mature in three to four weeks and, thereafter, remain dormant inside the galls in the stems until the following year. Infested barley plants are stunted and heads may fail to develop or, if formed, contain small, shrivelled kernels. In severely infested fields, the grain crop is considered a complete loss.There are six speoies of parasites known to attack H. hordei in Prince Edward Island, and all of them are chalcids that closely resemble the pest. Parasite eggs are deposited in the stem with the host and the larvae attack and destroy H. hordei larvae and then complete their development inside the galls. In addition to biological control by natural parasites, the other major natural control agent is considered to be weather, combinations of moisture, humidity, and temperature. However, further investigations are necessary to establish the influence of these different factors.