OOTAXONOMY

This section aims to provide a basic understanding of the phasmid egg, giving a brief introduction and describing the parts of it.

The phasmid egg is more important than it may at first appear, because it has taxonomic value. Thanks to this it has been able to differentiate and classify morphologically similar species; otherwise, it would have been almost impossible.  Obviously this is due to differences between the eggs of each species. For instance, operculum and micropylar plate are different for each species.

Ootaxonomy was not considered in this field. The terminology used today to describe the eggs of phasmids is narrated by J.T. Clark Sellick (Clark, 1976).

 

 

General structure

Fig. 2.-General structure of the egg
PSG 9.- Extatosoma tiaratum (Macleay, 1826)

Surface

The rigid external layer of the egg is the chorion. The main functions are to protect the embryo and to let breath through pores called aeropyles. In the dorsal area of the chorion there is the micropylar plate and in it the micropylar cup, where the sperm entered.

The operculum is the top that closes the egg, located in the anterior area of this one. When the egg hatches the operculum drops out letting the nymph go out. On it lies the capitular stalk and the capitulum.

Fig. 3.- Micropylar cup detail in egg of Extatosoma tiaratum tiaratum (Macleay,1826).

Inside the egg

Following the chorion there is the vitelline membrane which is formed by a endocuticle and epicuticle. Next, we find the yolk which contains the nutrient reserves. Finally, there is the core.

 

Different morphologies

Fig.1.-Examples of variety in shape and size in different species.

There is a great variety, depending on the species, in terms of shape, size, texture, etc.. In some cases they are quite resilient (e.g. Eurycnema goliath (Gray, 1834)) and in others the opposite (e.g. Ramulus artemis (Saussure, 1870)).
Some may be sticky, usually in the ventral area (e.g. Sipyloidea sipylus (Westwood, 1859)) to adhere to surfaces.
Depending on the species, the capsules might have smooth or rough surfaces and sometimes with bumps or hair.

Occasionally, the eggs appearance is not random. A classic example is the Extatosoma tiaratum, which tricks Leptomyrmex ants into believing they are seeds. They are taken to the warehouses of the anthill and so the eggs are safe from predators and also in good incubation conditions. If this was not enough, at birth the nymph is so similar to ants in appearance and behaviour that they go unnoticed while escaping from the anthill, heading for the trees in which they are fed.

 

Pictures of some eggs (Sorted by family)

INFRAORDER ANAREOLATAE

Family Diapheromeridae

Bacteria horni
Hemiplasta falcata
Necroscia annulipes
Paramenexenus laetus
Sipyloidea meneptolemus
Sipyloidea sipylus

Family Phasmatidae

Carausius morosus
Diapherodes gigantea
Eurycnema goliath
Extatosoma tiaratum
Lonchodes brevipes
Lonchodes jejunus
Lonchodiodes samarensis
Medauroidea extradentata
Neohirasea maerens
Parapachymorpha zomproi
Phenacephorus latifemur
Ramulus artemis
Ramulus nematodes
Spinohirasea bengalensis

INFRAORDER AREOLATAE

Family Bacillidae

Clonopsis gallica

Family Heteropterygidae

Aretaon asperrimus
Epidares nolimetangere
Heteropteryx dilatata
Trachyaretaon carmelae
Trachyaretaon sp. "Negros"

Family Phylliidae

Phyllium philippinicum

Family Pseudophasmatidae

Hypocyrtus scythrus
Lamponius guerini
Malacomorpha guamuhayense
Peruphasma schultei