Predation and avoidance of tough leaves by aquatic larvae of the moth Parapoynx rugosalis (Lepidoptera: Pyralidae)

Abstract.

• 1 Aquatic larvae of the pyralid moth Parapoynx rugosalis Möschler repeatedly construct protective cases by cutting portions (discs) from leaves of the waterlily Nymphaea ampla and sandwich themselves between the disc and the underside of the host leaf. Construction of a new case requires leaving the old case, thus increasing exposure to predators and parasites.
• 2 In an experiment, larvae with protective cases experienced no mortality due to predation by fish, whereas larvae without cases experienced substantial predation.
• 3 In a series of choice tests, larvae preferentially selected young, tender leaves over old, tough leaves for construction of cases, and larvae spent significantly less time completing their shelters when cutting discs from young, tender leaves.
• 4 A partial explanation of why larvae select young, tender leaves for construction of their protective shelters may be that exposure time to predators during construction is minimized.
• 5 The same mechanism linking preferences for tender leaves to reduced exposure to predators during construction may also apply to other insect herbivores exhibiting leaf-rolling or case-building behaviour.

     

The complete mitogenome of Parapoynx crisonalis (Walker, 1859) (Lepidoptera: Crambidae), with phylogenetic relationships amongst three acentropine larval forms

The larvae of Parapoynx crisonalis (Walker, 1859) is an important pest in China, causing significant damage on the aquatic crops. To improve the management of P. crisonalis and demonstrate the phylogenetic relationships amongst Pyraloidea, the complete mitochondrial genome (mitogenome) sequences of four aquatic pyralid moths, which belong to three acentropine larval forms – Parapoynx-type, Nymphula-type and Potamomusa-type, and twenty-three terricolous pyralids were compared. The complete mitogenome P. crisonalis, a typical parapoynx larval species, was 15,374 base pairs in length and included 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and an A + T-rich region. The phylogenetic analysis revealed that all the aquatic acentropine moths formed a monophyletic clade with strong phylogenetic support via maximum likelihood and Bayesian methods with a bootstrap value of 100% and a posterior probability of 1.00. The Potamomusa-type was more closely related to the Nymphula-type than to the Parapoynx-type.     

中国水螟亚科二新种记述(鳞翅目:草螟科)

记述了采自天津及河北、福建等地的水螟亚科Nymphulinae 2新种, 即 环波水螟Paracymoriza convallata, sp. nov.和白筒水螟Parapoynx candida, sp. nov..模式标本保存于南开大学生物系, 天津.1. 环波水螟Paracymoriza convallata,新种(图1,3)前翅长♂9.0 mm.正模♂, 福建永泰县青云山 (25.52°N,118.57°E),550 m,2002-Ⅸ-18,王新谱采.新种与华南波水螟Paracymoriza laminalis (Hampson) 相似,主要区别在新种前翅中线外白区前缘封闭;雄性外生殖器抱器瓣基部较窄,端部较圆.2. 白筒水螟Parapoynx candida,新种(图2,4～5)前翅长♂11.5～12.0 mm;♀11.5 mm.正模♂,天津武清县 (39.31°N,116.51°E),1976-Ⅵ-22, 王印来采.副模1♂,天津市板桥农场(38.52°N,117.28°E),1976-Ⅵ(采集人不明);1♀,河北大城县 (38.40°N,116.39°E),1976-Ⅵ-12 (采集人不明).此新种与重筒水螟Parapoynx stratiotata (Linnaeus) 相近,区别在于新种外横线至翅外缘白色;雌性外生殖器无明显囊突.     

基于外部形态特征量化分析判别菱角水螟幼虫龄期

【目的】本实验拟为田间准确快速判别菱角水螟Parapoynx crisonalis(Walker)幼虫龄期提供一种新方法,以便监测其发生规律、预测其发生时间。【方法】本研究通过对幼虫头壳宽、复眼距、体宽和体长4项外部形态指标的测量,运用Crosby生长法则和线性回归分析方法,结合各项指标的频次分布进行分析。【结果】各龄幼虫头壳宽平均值的变异系数和Crosby指数最小,为判别幼虫龄期的最佳分龄指标,幼虫期共分为5龄,1~5龄的头壳宽分别为(0.2493±0.0053)、(0.3454±0.0018)、(0.5079±0.0031)、(0.7419±0.0190)和(1.1287±0.0369)mm,其与龄期数呈线性关系。通过实验室饲养观察菱角水螟幼虫蜕皮次数验证该虫幼虫期分为5个龄期。【结论】头壳宽为判定菱角水螟幼虫龄期的最佳指标,复眼距次之。     

Larvae of Nymphulinae (Lepidoptera: Pyralidae) associated with Hydrilla verticillata (Hydrocharitaceae) in North Queensland

Abstract  Australian Nymphulinae are a diverse group of moths with aquatic caterpillars that probably play an important role in determining the composition and abundance of aquatic macrophytes in Australian freshwater systems. Less than 10% of the nymphuline larvae in Australia have been described. As part of a project to develop biological control agents for hydrilla, Hydrilla verticillata , we encountered a variety of Nymphulinae larvae feeding on this and other aquatic plants. We illustrate, describe and provide a key to five species of Nymphulinae larvae ( Ambia ptolycusalis (Walker), Parapoynx diminutalis Snellen, Hygraula nitens Butler, Margarosticha repititalis (Warren) and Theila siennata (Warren)) that feed on hydrilla in North Queensland. Information on their host plants also is included. Our field research indicates that none of these species should be considered as potential biological control agents for hydrilla.     

快速鉴别菱角水螟雌雄蛹的方法

【目的】本研究拟建立一种快捷、准确地鉴别菱角水螟Parapoynx crisonalis(Walker)蛹性别的方法。【方法】基于蛹的腹部末端第8、9两腹节的腹面外部形态学特征进行判别。【结果】雌雄蛹的腹面外部形态学特征主要区别在于雄蛹第8腹节平滑无裂缝,第9腹节中央具一较短纵裂缝,其两侧具明显的半圆形瘤状突起,而雌蛹第8腹节中央具一长纵裂缝,其两侧较为平坦、无明显凸起。依据该特征鉴别菱角水螟蛹雌雄的准确率为100%。【结论】该方法在田间进行雌雄蛹快速鉴别行之有效,对提前掌握菱角水螟田间性比、下一代种群动态的预测预报工作具有重要意义。