Determination of Larval Instars of Semanotus bifasciatus (Coleoptera: Cerambycidae) Based on Frequency Distributions of Morphological Variables

2020 ◽  
Vol 55 (3) ◽  
pp. 405-415
Author(s):  
Na Li ◽  
Lei Wu ◽  
Yongxin Geng ◽  
Danfeng Wei ◽  
Min Chen
Keyword(s):  
Body Length ◽  
Larval Instar ◽  
Head Capsule ◽  
Larval Instars ◽  
Frequency Distributions ◽  
Larval Stages ◽  
Field Investigations ◽  
Mandible Length ◽  
Morphological Variables

Abstract Semanotus bifasciatus Motschulsky (Coleoptera: Cerambycidae) is one of the most destructive pests of Platycladus trees in China. Morphological measurements, such as head capsule (HC) width, can be very useful and practical indicators for identifying larval instars of coleopteran species. In this study, six morphological variables, including HC width, pronotum width, mandible length and width, and body length and width were measured to determine the instars of field-collected larvae of S. bifasciatus. Both the HC width and pronotum width were reliable parameters for determining the instar and stage. Larvae of S. bifasciatus were divided into eight instars; we detected strong relationships between larval instar and both the HC width (R2 = 0.9640) and pronotum width (R2 = 0.9549). The ranges of body widths and lengths for each instar are provided as reference values for distinguishing among larval stages in field investigations.

scholarly journals Breaking the rule: Five larval instars in the podonomine midge Trichotanypus alaskensis Brundin from Barrow, Alaska

2018 ◽  
Author(s):  
Alec R. Lackmann ◽  
Malcolm G. Butler
Keyword(s):  
Life Cycle ◽  
Larval Instar ◽  
Adult Emergence ◽  
Head Capsule ◽  
The Arctic ◽  
Larval Instars ◽  
Daily Monitoring ◽  
Field Samples ◽  
Standard Life ◽  
Capsule Size

Except for one unconfirmed case, chironomid larvae have been reported to pass through four larval instars between egg and pupal stages. We have observed a fifth larval instar to be a standard life-cycle feature of the podonomine Trichotanypus alaskensis Brundin 1966 in tundra ponds on the Arctic Coastal Plain near Barrow, Alaska. T. alaskensis has a one-year life cycle in these arctic ponds. Adults emerge in June ~2-3 weeks after pond thaw, then mate and oviposit; most newly-hatched larvae reach instar IV by October when pond sediments freeze. Overwintering larvae complete instar IV within a few days of thaw, then molt again to a fifth larval instar. Imaginal discs, normally seen only during instar IV in Chironomidae, develop across both instars IV & V prior to pupation and adult emergence. While monitoring larval development post-thaw in 2014, we noticed freshly-molted T. alaskensis larval exuviae a week or more prior to any pupation by that species. In 2015-16 we reared overwintering instar IV larvae from single pond sources, individually with daily monitoring, through molts to instar V, pupa, and adult. Some overwintering instar II and III larvae were reared as well, but were few in number. During 2016 we also reared T. alaskensis progeny (from eggs) through instar II, thus documenting head capsule size ranges for all five instars in a single pond’s population. Without individual rearings, the fifth larval instar was not readily apparent for two reasons: 1) The molt itself occurs immediately after thaw and is so synchronous it is difficult to discern in daily field samples. 2) The head capsule size increment between instars IV-V is much lower than the ratio predicted by the Brooks-Dyar Rule. Up through instar IV, the Brooks-Dyar ratio for T. alaskensis ranged 1.30-1.61, but during the IV-V molt head capsule dimensions (sexes pooled) increased by a ratio of 1.09 – comparable to the magnitude of sexual dimorphism in head capsule size within each of the final two larval instars. Individual rearings coupled with 2014-2016 field surveys in nine other ponds suggest that five larval instars is an obligatory trait of this species at this location. As this is the first confirmed case of five larval instars in a chironomid, the phylogenetic uniqueness of this trait needs further investigation.

scholarly journals Formation of Pattern and Diagnostic Instar Features of the Head in Caterpillars from Genus Peridea (Lepidoptera, Notodontidae)

2009 ◽  
Vol 43 (1) ◽  
pp. e-15-e-24
Author(s):  
I. Dolinskaya
Keyword(s):  
Pattern Formation ◽  
Larval Instar ◽  
Head Capsule ◽  
Diagnostic Character ◽  
Key To Species ◽  
Larval Instars ◽  
Diagnostic Characters ◽  
Ontogenetic Stages ◽  
First Time ◽  
Taxonomic Relations

Formation of Pattern and Diagnostic Instar Features of the Head in Caterpillars from Genus Peridea (Lepidoptera, Notodontidae) Pattern and colouration of caterpillar head of all larval instar of 7 species from genus Peridea Stephens, 1828 are studied. Formation of caterpillar head pattern in ontogenesis is discussed. Diagnostic characters, both specific and larval instars, are recorded for the first time. Key to species according to larval instars is given. Evidently, only larvae of the 1st instar demonstrate different directions in the pattern formation. This characteristic can be used for clearing of taxonomic relations in the genera and on the earliest ontogenetic stages (1st larval instar) only. In the following (2nd-5th) instars, the pattern became more or less of the same type. It depends on stripes shape or colouration only and can serve as good specific diagnostic character. To determine larval instar, both width of the head capsule and head pattern should be taken into account.

scholarly journals Knockout silkworms reveal a dispensable role for juvenile hormones in holometabolous life cycle

2015 ◽  
Vol 112 (31) ◽  
pp. E4226-E4235 ◽  
Author(s):  
Takaaki Daimon ◽  
Miwa Uchibori ◽  
Hajime Nakao ◽  
Hideki Sezutsu ◽  
Tetsuro Shinoda
Keyword(s):  
Larval Instar ◽  
Status Quo ◽  
Mrna Expression Level ◽  
Larval Life ◽  
Larval Instars ◽  
Larval Stages ◽  
Juvenile Hormones ◽  
Competence Factor ◽  
Mosaic Analysis ◽  
Independent Mechanism

Insect juvenile hormones (JHs) prevent precocious metamorphosis and allow larvae to undergo multiple rounds of status quo molts. However, the roles of JHs during the embryonic and very early larval stages have not been fully understood. We generated and characterized knockout silkworms (Bombyx mori) with null mutations in JH biosynthesis or JH receptor genes using genome-editing tools. We found that embryonic growth and morphogenesis are largely independent of JHs in Bombyx and that, even in the absence of JHs or JH signaling, pupal characters are not formed in first- or second-instar larvae, and precocious metamorphosis is induced after the second instar at the earliest. We also show by mosaic analysis that a pupal specifier gene broad, which is dramatically up-regulated in the late stage of the last larval instar, is essential for pupal commitment in the epidermis. Importantly, the mRNA expression level of broad, which is thought to be repressed by JHs, remained at very low basal levels during the early larval instars of JH-deficient or JH signaling-deficient knockouts. Therefore, our study suggests that the long-accepted paradigm that JHs maintain the juvenile status throughout larval life should be revised because the larval status can be maintained by a JH-independent mechanism in very early larval instars. We propose that the lack of competence for metamorphosis during the early larval stages may result from the absence of an unidentified broad-inducing factor, i.e., a competence factor.

scholarly journals Morphology of immature stages of Helophorus (Gephelophorus) auriculatus (Coleoptera, Helophoridae)

2020 ◽  
Vol 60 (1) ◽  
pp. 319-332 ◽  
Author(s):  
Yusuke N. Minoshima ◽  
Reiya Watanabe
Keyword(s):  
Head Capsule ◽  
Immature Stages ◽  
Taxonomic Character ◽  
Larval Instars ◽  
Larval Stages ◽  
First Instar ◽  
Egg Case ◽  
Morphological Transformations

The morphology of immature stages of Helophorus (Gephelophorus) auriculatus Sharp, 1884 is described. This is the first description of the larva and pupa of the subgenus Gephelophorus Sharp, 1915. We describe the morphology of the egg-case, all larval stages (first to third instar, including chaetotaxy of the head) and pupa. Morphological transformations between larval instars were examined. Head chaetotaxy was nearly identical between instars. Ventral teeth on the nasale, considered as a useful taxonomic character, were absent in the first instar but well developed in later instars. Chaetotaxy differed among the subgenera Gephelophorus, Helophorus and Lihelophorus in the length and shape of setae on head capsule and maxilla. Pupal morphology was similar to that of previously described pupae: H. (Helophorus) aquaticus (Linnaeus, 1758) and H. (Rhopalohelophorus) orientalis Motschulsky, 1860. A key to families of the Hydrophiloidea of Japan based on larval characters is provided.

scholarly journals Characterization of the larval stages of Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) using head capsule width

2001 ◽  
Vol 61 (1) ◽  
pp. 125-131 ◽  
Author(s):  
O. FRANCISCO ◽  
A. P. do PRADO
Keyword(s):  
Age Structure ◽  
Developmental Rate ◽  
Head Capsule ◽  
Larval Instars ◽  
Alphitobius Diaperinus ◽  
Larval Stages ◽  
Mean Width ◽  
The Mean ◽  
Coleoptera Tenebrionidae

The mean width (n = 5) of the cephalic capsule instar of Alphitobius diaperinus was determined. The larvae were reared at 27ºC (± 0.1ºC). The result showed that A. diaperinus has eight larval instars. The head capsule of the 1st instar larvae measured x = 0.228 (SD = 0.0192) and the last instar larval measured x = 1.339 (SD = 0.0436). The developmental rate, determined by Dyar-Hutchinson's rule, was 1.29. These data may be useful for studies on phenology and age structure of A. diaperinus in the field.

scholarly journals Thermal summation model and instar determination of all developmental stages of necrophagous beetle,Sciodrepoides watsoni(Spence) (Coleoptera: Leiodidae: Cholevinae)

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e1944 ◽  
Author(s):  
Pavel Jakubec
Keyword(s):  
Forensic Entomology ◽  
Developmental Stages ◽  
Larval Instar ◽  
Head Capsule ◽  
Common Species ◽  
Standard Errors ◽  
Future Studies ◽  
Post Mortem Interval ◽  
Holarctic Region

Necrophagous beetles are underrepresented in forensic entomology studies despite their undeniable utility for the field. In the present article, information is presented regarding the developmental biology and instar determination ofSciodrepoides watsoni(Spence, 1813), a very common species occurring across the Holarctic region. Wild collected beetles were kept in climate chambers at constant temperature (12, 15, 18, 21 and 28 °C) and their development was regularly documented. Parameters of thermal summation models and standard errors were calculated for each developmental stage. These models may be used for an estimation of post-mortem interval in legal investigations after further validation on local populations ofS. watsoni. An additional methodology is introduced for future studies of size-based characteristics, addressing instar identification bias. The methodology provided estimations (mean, standard error and standard deviation) ofS. watsonilarval head capsule width for preliminary larval instar determination. The methodology may be used with other morphological features to improve instar determination accuracy.

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