Determination of Larval Instars of the White-Pine Weevil1 by Head-Capsule Measurements2,3

1970 ◽  
Vol 63 (6) ◽  
pp. 1573-1575 ◽  
Author(s):  
Dan M. Harman
Keyword(s):  
Head Capsule ◽  
White Pine ◽  
Larval Instars

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 Host plant effect on the number of moultings and head capsule width of the gypsy moth caterpillars

2012 ◽  
pp. 127-138
Author(s):  
Slobodan Milanovic ◽  
Sladjan Milanovic
Keyword(s):  
Gypsy Moth ◽  
Head Capsule ◽  
Larval Instars ◽  
Head Capsule Width ◽  
Sessile Oak ◽  
Turkey Oak ◽  
English Oak ◽  
Host Plant Effect ◽  
Oak Leaves

The effect of four oak species: Turkey oak, Hungarian oak, sessile oak and English oak on the number of moultings and head capsule width of the gypsy moth caterpillars was researched. Host plants have a statistically significant effect on the number of both male and female larval instars. The highest number of larval instars was recorded for caterpillars fed on sessile oak leaves, and the lowest number was recorded for those fed on Turkey oak leaves. Females reared on Hungarian oak and English oak leaves had a normal number of larval instars. Except for 1st instar caterpillars, all other larval instars showed a statistically significant host plant effect on the head capsule width. The widest head capsules were found on caterpillars fed on Turkey oak leaves, and those fed on sessile oak leaves had the narrowest head capsules. The study data on head capsule widths can be practically applied in the determination of the optimal ratio of larval instars in the gypsy moth population, i.e. in the determination of terms for aerial spraying actions.

scholarly journals Determination of larval instars in Chironomus sancticaroli (Diptera: Chironomidae) using novel head capsule structures

2013 ◽  
Vol 30 (2) ◽  
pp. 211-216 ◽  
Author(s):  
Vinicius S. Richardi ◽  
Débora Rebechi ◽  
José M. R. Aranha ◽  
Mário A. Navarro-Silva
Keyword(s):  
Head Capsule ◽  
Larval Instars

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.

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