Protrusion like the horn of the first instar larva of a dragonfly

The final renewal day of this page is January 28, 2005.

 The first instar larvae of the dragonflies of several species have a protrusion like the horn to the head. This protrusion becomes more big when it becomes a second instar larva. However, this protrusion is fading away as a larva grows. This protrusion does not have an official name and even the work is not clear. This protrusion appears in the short period of while when becoming a first instar larva from a prolarva, when a dragonfly incubates. The species that has such a protrusion in Zygoptera is less compared with Anisoptera.
 However, this protrusion is seen with Platycnemididae in the dragonfly that belongs to Zygoptera. Also, this protrusion is seen to Coenagrionidae of several species. This protrusion is seen with Sinictinogomphus clavatus, Ictinogomphus pertinax of Gomphidae.
Also there are comparatively many species that have the protrusion that is conspicuous to Libellulidae, Corduliidae. There is a big protrusion in an occipital lobe in Aeschnophlebia anisoptera, Aeschnophlebia longistigma, Boyeria maclachlani ofAeshnidae. The protrusion of Boyeria maclachlani is in the position even if it becomes a fainal instar larva.

Please click the image of the next one of them.

Platycnemis foliacea sasakii Copera annulata Ictinogomphus pertinax Sinictinogomphus clavatus
Aeschnophlebia longistigma Aeschnophlebia anisoptera Boyeria maclachlani Epitheca marginata
Deielia phaon Pseudothemis zonata Sympetrum croceolum Sympetrum uniforme
Sympetrum striolatum imitoides Nannophya pygmaea Ceriagrion melanurum Sympetrum depressius culum
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Size of the eggs of 22 species of dragonflies that used it in this page  

Species Adult Egg
Length(mm) Immediately after oviposition (mm) Hatching several hours ago (mm)
Mortonagrion selenion  27.0 0.85~0.17 1.00~0.22
Ceriagrion melanurum 38.5 0.95~0.20 1.07~0.25
Platycnemis foliacea sasakii  37.0 1.02~0.20 1.14~0.25
Platycnemis echigoana  * * 1.26~0.24
Copera annulata  42.5 1.18~0.19 1.30~0.24
Ictinogomphus pertinax 74.5 0.75~0.40 0.78~0.47
Sinictinogomphus clavatus 78.5 0.81~0.35 0.81~0.43
Boyeria maclachlani  83.5 1.84~0.38 1.92~0.50
Aeschnophlebia longistigma 70.5 1.51~0.33 1.74~0.44
Aeschnophlebia anisoptera 77.0 1.56~0.37 1.72~0.47
Epitheca marginata 51.5 0.73~0.36 0.86~0.46
Epophthalmia elegans 82.5 0.48~0.27 0.57~0.33
Cordulia aenea amurensis * * 0.77~0.43
Nannophya pygmaea 19.0 0.42~0.26 0.45~0.34
Deielia phaon 41.0 0.55~0.27 0.61~0.34
Sympetrum striolatum imitoides 44.0 0.55~0.35 0.61~0.43
Sympetrum depressius culum 34.5 0.55~0.31 0.59~0.36
Sympetrum frequens 39.5 0.58~0.32 0.61~0.38
Sympetrum kunckeli 34.5 0.52~0.32 0.53~0.38
Sympetrum croceolum  37.5 0.58~0.33 0.58~0.38
Sympetrum uniforme 47.0 0.47~0.28 0.52~0.35
Pseudothemis zonata 43.5 0.66~0.30 0.71~0.37