Life cycle changes during 12 successive generations of laboratory colonisation of the leafroller Cnephasia jactatana (Walker) (Lepidoptera: Tortricidae) on artificial diet

Abstract

Close monitoring of the lepidopteran leafroller Cnephasia jactatana under laboratory colonisation revealed few distinct effects of successive rearing on artificial diet on the life cycle. The second laboratory generation had a prolonged development time and altered sex synchronism in pupation and eclosion patterns. Some deleterious changes were observed in later generations, including decreases in fertility, egg hatch and sperm motility, failure of mating adults to separate, and pupal and adult malformations. These changes were not adaptive, but were due to incompatibility with the general purpose diet (GPD) used; they were absent under sub-colonisation on a sheepnut-bean based diet (SBD). Success in the laboratory colonisation of C. jactatana is attributed to a random mating protocol, choice of environmental conditions representing the wild habitat, and a rapid rate of population growth.     

Larval performance of two leafroller species on known and potential hosts

Two univoltine leafroller species,Archips argyrospila Walker andArchips rosana L., were reared from eclosion to adulthood on known or potential host plants. Both species were able to complete development on eight of the ten plants tested, the exceptions being apricot and peach. Rates of development differed among hosts, and indicated a range of host suitability. Differences in female pupal weights were apparent following the different rearing treatments, but these did not correlate with subsequent female fecundity. When development was compared between the two leafroller species,A. rosana had higher survivorship, more rapid development and higher female fecundity than didA. argyrospila, regardless of host. These findings indicate thatA. rosana may successfully exploit a wider host range than doesA. argyrospila. Comparisons of survivorship and developmental rates among hosts for each species of leafroller suggest that both species may have the potential for host-range expansion.     

The molluscan genus Cominella (Gastropoda: Buccinidae) at the Three Kings Islands

Abstract

Three endemic taxa of Cominella Gray are recorded from the Three Kings Islands, New Zealand. Cominella (Josepha) regalis n.sp. and C. (Josepha) quoyana griseicalx n.ssp. occur sympatrically in relatively shallow water (to c.50m), whereas C. (Eucominia) mirabilis mirabilis Powell is known only from c.180m. The history of colonisation by these taxa is hypothesised and discussed.     

Temporal variation in abundance of male and female spruce budworms at combinatory associations of light traps and pheromone traps

A 3‐year study (2014–2016) was conducted at Rocky Harbour near the west coast of Newfoundland, Canada, to record the abundance and phenology of adult spruce budworms captured at traps, using a factorial design (light traps and pheromone traps deployed contiguously or segregated spatially). Budworms were most abundant and occurred seasonally earlier in 2014 than in 2015 and 2016; these findings held generally true for males and females. The geographic setting of Newfoundland (large island isolated from the mainland by an oceanic barrier of >100 km across) provides an ideal location to discriminate local flight from long‐range immigrations; in our study, however, immigrations cannot be ruled out for any single day of trapping due to broad overlap in emergence patterns at Rocky Harbour relative to forest stands with known populations of budworms on the mainland. Based on moderate daily variation in adult abundance, however, major immigration events (defined as external deposition of budworms with large numerical amplitude) likely did not take place at Rocky Harbor between 2014 and 2016. Males were more abundant at light traps coupled with pheromone traps, whereas abundance of males at pheromone traps was similar with or without contiguous light traps. This outcome may be mediated by lower range of attraction for light traps (usually <100 m) and (generally assumed to be several hundreds of meters). Females were equally abundant at light traps with or without pheromone traps. As expected, males were captured earlier in the season at pheromone traps than at light traps, and females occurred later in the season due to protandry. The onset of flight observed at light traps or pheromone traps in 2015 and 2016 occurred 10–15 days later than simulated predictions; caution is thus warranted as to conclusions derived on computer modeling of adult emergence.     

A simple method to disperse eggs from lepidopteran scalelike egg masses and to observe embryogenesis

Various insect species lay tiny, thin- and soft-shelled eggs in a connected “egg mass”. Especially in several lepidopteran species, the structure of such clustered eggs is covered with complicated scale-like secretion, which has so far prevented analysis of individual embryos. However, few studies on methods to disperse egg clusters of such insects and to compare different methods have been carried out. To overcome these problems, we developed methods to separate egg masses into individual eggs, using two Tortricidae pests, Homona magnanima Diakonoff and Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae). The eggs were successfully separated from each other using potassium hydroxide and sodium hypochlorite. Although the separated eggs no longer continued their embryogenesis, fixation with heptane–paraformaldehyde, permeabilization with heptane–methanol, and staining with several dyes enabled easy observation of embryogenesis. This protocol is expected to be applicable to other insect taxa and will facilitate further morphological and genetic studies in insects that lay egg masses.     

Gas chromatography column as an ambient‐temperature volatile trap

Open‐tube volatile traps have largely been shunned in favor of solid adsorbent containing traps for the collection of volatile pheromones and attractants. Solid adsorbents require large solvent rinses and glass capillaries can be difficult to maneuver for the collection of volatiles from small or hard‐to‐reach odor sources. A gas chromatograph (GC) column (DB‐1), an open‐tube glass capillary, and a SuperQ^®‐containing capillary were compared for their collection efficiencies from rubber septa and live calling insects. All three traps captured similar ratios of test compounds from septa at airflows >10 ml per min. Eluting analytes from a packed adsorbent, SuperQ, required at least 30× more solvent than was required to collect all the pheromone from the open‐tube glass capillaries, and the GC column enjoyed an additional three‐fold reduced solvent volume compared to the glass capillary. Thus, analytes could be eluted from the GC‐column trap and directly analyzed on GC without solvent evaporation. We placed glass wool ‘plugs’ in both GC columns and glass capillaries and found no volatiles in these plugs, indicating that breakthrough did not occur during 1‐h collections at 25 ml per min. We demonstrate here that at ambient laboratory temperatures, a DB‐1 GC column effectively collects Oriental fruit moth sex pheromone volatiles from a rubber septum and live pheromone‐releasing moths. Release ratios of pheromone from rubber septa are consistent with earlier reports from static air systems, whereas the release ratio of the (Z)‐8‐dodecenyl alcohol (Z8‐12:OH) from female Grapholita molesta Busck (Lepidoptera: Tortricidae) differed from published results and is likely due to different collection methods or moth‐strain origin.     

Species composition and life histories of shelter-building caterpillars on Salix miyabeana

We studied the species composition and life history patterns of shelter‐building microlepidoptera on the willow Salix miyabeana in Hokkaido, northern Japan. We identified 23 microlepidopteran species across seven families that constructed leaf shelters. Species in Tortricidae and Pyralidae comprised approximately 90% of the total number of sampled shelter‐building microlepidoptera that reached adult eclosion in the laboratory. Seasonal changes in the density of leaf shelters showed two peaks: early June and mid‐August. In June, caterpillars of Gypsonoma bifasciata, Gypsonoma ephoropa, Acleris issikii and Saliciphage acharis were the principal shelter builders, while in August shelters were constructed primarily by caterpillars of Nephopterix adelphella, A. issikii and S. acharis. Approximately 90% of leaf shelters were constructed on the top portions of shoots, suggesting that most shelter‐building caterpillars prefer to build leaf shelters here.     

Statistical modelling of insect behavioural responses in relation to the chemical composition of test extracts

Abstract. The use of generalized linear models (GLM) for relating changes in insect behaviour to changes in the chemical composition of a plant extract is presented and applied to data from an experimental study of the olfactory response of Cydia pomonella L. (Lepidoptera: Tortricidae) to apple volatiles. The volatiles were collected from healthy apples, artificially damaged apples or apples infested with C. pomonella larvae (either instar I, IV or V). These treatments produced a blend of 23 major components and the chemical composition of the blends differed substantially amongst the treatments.
A statistically significant relationship was found between the concentration of hexyl hexanoate and 2-methylbutyl acetate in each extract and the number of moths moving upwind. Statistically significant models were developed which suggested that a relationship exists between the concentration of Z , E -α-farnesene, hexyl hexanoate and 2-methylbutyl acetate and the number and duration of movements made by the moths.
Subsequently Y-tube assays were carried out to validate the predictions made with respect to the orientation of mated female C. pomonella . The results of these assays confirm hexyl hexanoate as an attractant. There were indications that 2-methylbutyl acetate acted as a repellent although differences were not statistically significant. Previous bioassays have shown that C. pomonella displays a statistically significant negative linear dose–response to α-farnesene ( Hern & Dorn, 1999 ).
The statistical methods employed are very flexible and fairly easy to implement, offering the potential to screen plant extracts for bioactive compounds with a minimum of biological constraints. Their general applicability has yet to be demonstrated and as such these analyses only offer evidence of statistical relationships; the results must be validated by additional bioassays before conclusions can be drawn.