科: 牙蟲科 Hydrophilidae
地點: 赤柱
月份: 7

身體較圓, 很多時也被上白粉

科: 牙蟲科 Hydrophilidae
地點: 赤柱
月份: 7

身體扁和細長, 體長約5mm

Based on the paper "AN UPDATED CHECKLIST OF HALIPLIDAE, GYRINIDAE, DYTISCIDAE,nNOTERIDAE & HYDROPHILIDAE FROM HONG KONG", I have thought that Rhantus sp. does not occur in Hong Kong. However, I have encountered the larvae of Rhantus recently in Pat Sin Leng and Lai Chi Wo. Thus, I am not sure species 4 is Rhantus sp./ Hydaticus rhantoides. They can be identified by Pederzan's paper (1995):  Keys to the identification of the genera and subgenera of adult Dytiscidae (sensu lato) of the world (Coleoptera Dytiscidae)

These two genus is from different subfamilies. The main feature that used to distinguish between them is that: For Rhantus sp., it is from Colymbetinae and the eyes are emarginated above bases of antenna (indicated from the picture) while for H. rhantoides, the eyes are round and not emarginated

[ 本帖最後由 sykin 於 2016-8-5 15:28 編輯 ]

兩天前我在水口也見到品種3，很大機會是 Cybister sugillatus

大小亦符合日本保育社出版的《原色日本甲蟲圖鑑(II)》描述，大概在21mm-24mm之間

我同意ID是 黑綠真龍虱 Cybister sugillatus

與這裏的圖片比較, 頭部和胸部的斑紋沒有明顯分別。 腹部方面, 也同樣有很疏的點, 近尾的地方有暗斑
http://www.123rf.com/photo_22248 ... u-island-japan.html
在 張永仁 1998. 昆蟲圖鑑 中描述, 胸板兩側有橙斑, 也能在水口個體中找到這特徵

另外, 跟據這裏的分佈, 東亞的分佈主要是在小島上, 包括日本(琉球), 菲律賓, 印尼等, 而中國也有也有分佈, 所以香港是合理的分佈地點
http://faunaofindia.nic.in/PDFVo ... 14/01/0105-0110.pdf

而中文名稱是參考這裏:
http://www.guokr.com/blog/90184/

[ 本帖最後由 sswroom 於 2016-8-26 23:30 編輯 ]

Hydaticus vittatus
科: 龍蝨科 Dytiscidae
中文: 黃紋麗龍蝨
地點: 大嶼山

https://www.inaturalist.org/observations/18732187

也好, 因為計埋幼蟲就包括蜻蜓等等...

講緊甲蟲，關蜻蜓咩事