Linear Increment in Width of the Head Capsule of two Species of Sawflies

1956 ◽  
Vol 88 (1) ◽  
pp. 17-23 ◽  
Author(s):  
A. W. Ghent
Keyword(s):  
Head Capsule ◽  
Sawfly Larvae ◽  
Linear Increment

Interest in the growth of insect head capsules was aroused by the observation of Dyar (2) that for a number of lepidopterous larvae the ratio of the width of the larval head capsule in a given instar to that in the following instar tends to be constant throughout development, This observation, generally known as “Dyar's Law” or “Dyar's Rule”, has proven valid for many lepidopterous larvae, for whch it was proposed. Many attempts have been made to apply Dyar's Rule to insects of other orders. Various authors, notably Miles (6) and Taylor (71, have considered the application of Dyar's Rule to sawfly larvae, and although they report some inconsistencies, they conclude that the rule is useful if its application is restricted to checking upon the number of feeding instars. The head capsules of non-feeding prcpupal sawfly larvae are generally of the same size as those of the last feeding instar, so that this stage is not expected to satisfy Dyar's Rule.

Diatom- and Chironomid-Inferred Eutrophication of Bouchie Lake, British Columbia

2005 ◽  
Vol 40 (4) ◽  
pp. 418-430 ◽  
Author(s):  
Markus L. Heinrichs ◽  
Brian F. Cumming ◽  
Kathleen R. Laird ◽  
J. Sanford Hart
Keyword(s):  
British Columbia ◽  
Land Use Changes ◽  
Head Capsule ◽  
Relative Increase ◽  
Nutrient Concentrations ◽  
The Past ◽  
Nutrient Levels ◽  
Lower Head ◽  
Lower Oxygen ◽  
Historical Land Use

Abstract Diatom and chironomid analysis of sediments encompassing the past 400 years from Bouchie Lake, British Columbia, suggests two distinct periods of limnological conditions. Prior to 1950 AD, Fragilaria construens and F. pinnata are the most common diatom species, and Chironomus, Procladius and Tanytarsini dominate the chironomid record. Moderately low nutrient concentrations consistent with oligo-mesotrophic lakes are inferred. From 1950, the diatom assemblage is dominated by Stephanodiscus parvus, a eutrophic indicator, whereas the chironomid communities show a relative increase in littoral taxa coincident with lower head capsule abundance. Higher nutrient levels, specifically total phosphorus, which increased from 8 µg L-1 prior to 1950 to 20 µg L-1 currently, are coincident with midge communities indicative of lower oxygen concentrations. Observed biotic changes and nutrient levels inferred from the sediment core correspond to historical land-use changes.

The embryogenesis of the larval head of Simulium venustum Say (Diptera: Nematocera)

1969 ◽  
Vol 47 (4) ◽  
pp. 495-503 ◽  
Author(s):  
D. A. Craig
Keyword(s):  
Head Capsule ◽  
Single Structure

The embryogenesis of the larval head of Simulium venustum Say is reexamined, as the known accounts of simuliid embryology do not describe the origin of the cephalic fans. It is shown that the cephalic fans are derived from the premandibular appendages, that the cephalic apotome is composed of both labral and protocephalic elements, that the egg burster marks the posterior limit of the embryonic labrum, and that the ventral median portion of the larval head capsule is submental in origin. The single prothoracic proleg arises as a single structure late in development.The embryogenesis of the simuliid cephalic fans is compared with that of similar structures in other nematocerous larvae. It is concluded that the cephalic fans of simuliid and the mouth brushes of Aedes larvae are not homologous.It is proposed that the cephalic fans be renamed premandibular fans, that the postgenal cleft be renamed the submental cleft, and that the hypostomial teeth be renamed the mental teeth.

scholarly journals Life History of the Tamarind Weevil, Sitophilus linearis (Herbst) (Coleoptera: Curculionidae), on Tamarind Seed

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
James Adebayo Ojo ◽  
Adebayo Amos Omoloye
Keyword(s):  
Life History ◽  
Management Strategy ◽  
Head Capsule ◽  
Developmental Period ◽  
Growth Ratio ◽  
Egg Incubation ◽  
Tamarind Seed ◽  
Standard Procedures ◽  
Important Pest ◽  
History Of

The tamarind weevil, Sitophilus linearis Herbst (Coleoptera: Curculionidae), is an important pest of tamarind and other Caesalpinioideae. Investigating its life history is important in the implementation of management strategy. Its life history was monitored daily to understand its developmental biology on tamarind seed following standard procedures under laboratory conditions of 24–30°C temperature, 60–70% relative humidity, and 12L : 12D photoperiod. The egg incubation period lasted 3.17 ± 0.07 days. A mated female of S. linearis laid an average of 165 ± 5.78 eggs during an oviposition period of 86.8 ± 2.47 days. There were four larval instars, with a total larval developmental period of 16 days. The pupal period lasted 8 days, and adult lived 108.5 ± 3.61 days. The overall growth ratio for the four instars was 1.33. There was a regular relationship and significant correlation (r=0.94) between the stages of larval development and head capsule width.

Leadership Behaviour in Sawfly Larvae Perga dorsalis (Hymenoptera: Pergidae)

Oikos ◽  
1997 ◽  
Vol 79 (3) ◽  
pp. 450 ◽  
Author(s):  
P. Weinstein ◽  
D. A. Maelzer
Keyword(s):  
Sawfly Larvae ◽  
Leadership Behaviour

P25 gene regulation in Bombyx mori silk gland: two promoter-binding factors have distinct tissue and developmental specificities

1992 ◽  
Vol 12 (12) ◽  
pp. 5768-5777
Author(s):  
B Durand ◽  
J Drevet ◽  
P Couble
Keyword(s):  
Bombyx Mori ◽  
Head Capsule ◽  
Regulatory Elements ◽  
Silk Gland ◽  
Related Factor ◽  
Developmental Studies ◽  
Hormonal Change ◽  
Specific Expression ◽  
Gland Cells ◽  
Gene Status

The gene encoding the silk protein P25 is expressed in the posterior silk gland of Bombyx mori with strict territorial and developmental specificities. The cis-acting regulatory elements previously located within the 441-bp 5' proximal sequence of the gene were examined for protein-binding capacities. We identified two factors, BMFA and SGFB, that lead to prominent band shifts and the target sites for which are included in a region homologous to the fibroin gene enhancer sequence. Analysis of the tissue-specific incidence of both factors showed that BMFA is ubiquitous, whereas SGFB is restricted to the silk gland cells. However, SGFB was found in both posterior and middle silk gland cells and therefore likely directs organ-specific, but not territory-specific, expression. Developmental studies throughout the fourth larval molt, at which the P25 gene status changes from derepressed to repressed, revealed that BMFA is reversibly modified at the transition from intermolt to molt. Indeed, the preexisting BMFA is replaced by a structurally related factor, BMFA', during the 2 h following head capsule apolysis. The exact temporal coincidence of this conversion with the onset of gene repression suggests that BMFA' is involved in transcription inactivation and likely results from a transduction process initiated by the hormonal change at molting.

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 Australian mycophagous species of the genus Deplorothrips (Thysanoptera, Phlaeothripinae)

Zootaxa ◽  
2016 ◽  
Vol 4208 (3) ◽  
pp. 201
Author(s):  
LAURENCE A. MOUND ◽  
DESLEY J. TREE
Keyword(s):  
New Species ◽  
Body Size ◽  
Head Capsule ◽  
Identification Key ◽  
Structural Polymorphism ◽  
First Time

The genus Deplorothrips Mound & Walker is recorded from Australia for the first time. The genus is found widely across the continent, and descriptions and an illustrated identification key are provided to 14 new species. These have been found living on dead twigs and branches, particularly of Eucalyptus trees. Typical members of this genus have short maxillary stylets that are scarcely retracted into the head capsule, but some of the species have more deeply retracted stylets. Structural polymorphism is recorded in several species, associated both with sex and with body size. Remarkable variation is recorded for some species in the number of sense cones on the antennal segments. 

Sign in / Sign up

Export Citation Format

Share Document