Reproductive traits and number of matings in males and females of Cerambyx welensii (Coleoptera: Cerambycidae) an emergent pest of oaks

Abstract

The longhorn beetle Cerambyx welensii is an emerging pest involved in oak decline episodes, whose damage is increasingly reported in dehesa open woodlands. Knowledge of the reproductive biology of C. welensii is a crucial goal due to its new pest status. In this study, we assess the reproductive traits of both sexes in the laboratory (25°C and 60% relative humidity ). In females, body length was 44.9 ± 0.9 mm (mean ± SE), fecundity 132 ± 12 eggs, fertility 70 ± 1 %, longevity 70 ± 3 days, preoviposition period 2 ± 0.2 days, oviposition period 44 ± 3 days and postoviposition period 19 ± 3 days. Fecundity was positively correlated with female size, longevity and oviposition period. Daily fecundity was 3.0 ± 0.2 eggs/day and showed a fluctuating synovigenic pattern with a slight decreasing trend over time. Egg length was 4.24 ± 0.01 mm and egg volume 8.14 ± 0.04 mm3. Egg size was correlated with female size but the relative size of eggs was larger in smaller females. Incubation time was 13.9 ± 0.1 days and hatching did not depend on egg size. Neonate size was positively correlated with egg length. Females were polyandrous (more than 20 lifetime matings) but multiple mating did not increase fecundity, fertility or longevity. In males, body length was 43.7 ± 0.6 mm and longevity 52 ± 3 days. Unlike with females, longevity was positively correlated with male size. Males were polygynous (up to 30 lifetime matings) but mating history did not affect male longevity. Rather to the contrary, long-lived males mated more times because they had more mating chances. Lastly, C. welensii reproductive traits were compared with those other Cerambycidae species and discussed from an adaptive perspective. Our data will be useful to improve management of C. welensii in order to prevent or mitigate its impact in dehesa woodlands and other oak forests.

Dispersal differences of a pest and a protected Cerambyx species (Coleoptera: Cerambycidae) in oak open woodlands: a mark–recapture comparative study

“…It follows that if flight proneness does not diminish with adult age, longevity will correlate positively with dispersal rate. Maximum life spans recorded (39-66 days depending on species and sex) are in agreement with mean longevities reported in a recent laboratory study in which Cw adults were held in optimal conditions from emergence (Torres-Vila et al, 2016). In the case of Cc, our longevity field estimates were much higher than values previously reported (El Antry, 1999).…”

“…Adults feed mainly on tree exudates and sap, while larvae are xylophagous. Daily activity of adults (feeding, mating and egg-laying) takes place typically at dusk and in the early evening, but it may also occur during the day (Bense, 1995;Vives, 2000;Torres-Vila et al, 2016). Larvae bore increasingly wider and longer galleries into wood, causing huge physiological, mechanical and structural damage, and even tree death (Torres-Vila et al, 2012;Sallé et al, 2014).…”

“…Some living adults that were excessively damaged, forceless or in torpor were recorded but not released (<1%). About half of adults (for each species-sex combination) were allowed to feed ad libitum prior to release on a saturated sugar-water paste simulating host tree exudates (Torres-Vila et al, 2016). Marked adults were returned to the field and released early in the morning (to avoid midday heat-derived stress), depositing them one by one in the main branches and crown of the release tree.…”

“…In 2014, adults were marked using the paint-based method previously used both in the field with pine sawyers and in the laboratory with Cw (Torres-Vila et al, 2016). A fine layer of waterproof white pen correction fluid (Tipp-ex, BIC, Clichy, France) was applied on both elytra to form a small white rectangle (about 5 × 10 mm 2 ) and then marked with correlative numbers written on the white rectangle with a black permanent fine marker pen (Lumocolor, Staedtler, Nuremberg, Germany).…”

Dispersal and Propagule Pressure of Botryosphaeriaceae Species in a Declining Oak Stand is Affected by Insect Vectors

“…These two beetles, differing from bark beetles, lay eggs without penetrating the oak bark; therefore, their importance in the spread of fungal infection may appear less important. Nonetheless, they do bring fungal propagules into direct contact with oak trees, since the egg-laying activity of C. welensii includes probing the bark with its ovipositor, as well as laying eggs into bark crevices and pruning wounds [37]. Thus, propagules are highly likely to come into contact with suitable entry sites.…”