Morphological characteristics of the different developmental stages and larval body hair of Camponotus japonicus

Author of the article:YANG Lü** ZHANG Liang-Liang MA Ruo-Qing HE Hong***

Author's Workplace：Key Laboratory of National Forestry and Grassland Administration for Control of Forest Biological Disasters in Western China, College of Forestry, Northwest A&F University, Yangling 712100, China

Key Words：growth and development period; morphological characteristics; larvae; instar; body hair

Abstract：  [Aim]  To describe the morphological characteristics and developmental periods of different developmental stages of Camponotus japonicus (eggs, larvae, pupae and the first-generation workers), focusing on the division of larval instars, and analyze the types of larval body hair of different instars. [Methods]  The morphological characteristics of eggs, larvae, pupae, and adults (first-generation workers) were observed under a light microscope. Larval instars were classified according to head capsule width, and the types of larval body hair of different instars were observed using both light microscopy and scanning electron microscopy. [Results]  (1) Daily egg production of new queens was about (2±1) eggs, the egg stage was (13±1) d, the larval stage was (9±2) d, and the pupal stage was (15±1) d. The bodies of newly emerged workers were pale and soft, but darkened and hardened in subsequent days. (2) Larvae can be divided into three instars according to head capsule width. The head capsule widths of the 1st, 2nd and 3rd, instars were (0.488±0.003), (0.625±0.003), and (0.737±0.004) mm, respectively. (3) The body hair of larvae varies greatly among instars. First instar larvae have more curly, hooked, long hairs than 2nd instar larvae. Third instar larvae have uniform body hair but no curly, hooked, long hair. (4) The body hair types of larvae can be divided into 6 major categories and several subtypes, including simple, bifid, 3-branched, 4-branched, 5-branched and 6-branched. The number of forked hairs increases with larval instar. [Conclusion]  Larvae of C. japonicus have dense body hair, the types of which vary greatly among instars. Younger larvae have curlier, hook-like, long hairs, which enables them to clump together and facilitates their transportation by workers. Larval instars can be distinguished on the basis of head capsule width, but body hair type may provide another means of identifying the larval instars of this species.