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Anatomy & Physiology of the Ovum

 

*The Ovum 

*General variation in shape of Ova according to Family

 

The Ovum

Like all organisms who reproduce sexually butterfly mating takes place and is often preceeded by a form of courtship.

Mating may take place several times during the lifetime of the male and female butterfly. 
The duration of mating varies among the species, often lasting 1-2 hours and somtimes many hours longer.

After mating the sperm (male gametes) are stored in an organ called the
corpus bursa in the abdomen of the female
butterfly.  It is from this resevoir of sperm that the eggs (
female gametes) are fertilised.

Each egg produced in the ovary of the female,  when mature, is surrounded by a hard shell called the
chorion and at one 
end of the egg there is one or many small openings called micropyles.  Male sperm enters the egg through one of these
micropyles as the egg passes the sperm sac (corpus bursa)  on its way down the oviduct during egg-laying.

 

BrownHairstreak photo by DHardiman
Brown Hairstreak ovum with 
micropyle visible

With fertilisation the male and female gametes fuse to form a  fertilised nucleus within the egg. 

This produces 

At this EGG stage of the life cycle of the butterfly the embryonic cells differentiate into specific tissues and organs required for 
a crawling, leaf eating and periodically moulting LARVA (caterpillar) but some embryonic cells, that play no part in the insects
larval life, remain dormant in a number of  places in the caterpillar's body until a later stage of the life cycle. 

These collections of formative cells are called imaginal buds because they develop into organs more suited for a flying, sucking and reproducing ADULT BUTTERFLY (imago).

Since male and female gametes possess only half the number of chromosomes (haploid number) found in their parent body cells (diploid number)  fusion of the male and female gametes ensures that 

After fertilisation the female butterfly must find a suitable and safe place to deposit her eggs (oviposit).  This place must 
also provide enough food for the developing young caterpillars.

Some species of female butterflies simply scatter their eggs during flight above the host plant/s.  However most female 
butterflies must search for the appropriate host plant/s on which to lay her eggs.

As all plants contain certain organic compounds that are specific to the plant, the female butterfly, through chemoreceptors on her legs and elsewhere, can detect these compounds and so recognise appropriate plant species or groups of species upon which her young can feed.

Once a host plant/s is found and depending on the species of  butterfly, eggs may be laid 

on a particular part of the plant (or nearby), remaining attached by a sticky secretion.

In most species the egg changes colour after laying,  becoming darker as the young embryo develops and sometimes the young
larva becomes visible through the shell prior to hatching.

 

Ova of Large White Butterfly

newly laid eggs
.

eggs  prior to hatching

 

Eggs take a variable amount of time to hatch, usually around 10 days but longer if hibernation occurs at this stage.

When fully developed the larva (caterpillar) eats its way out of the eggshell and some species often consume the rest of the shell before feeding on its food plant.

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General variation in shape of Ova according to Family

 


 


 

 

           DHardiman 2002 

                    

Hesperidae

Pieridae

Lycaenidae

Nymphalidae

Satyridae

 

Pieridae

Large White ovum,  DHardiman
Large White 


Large White

Small White ovum,  DHardiman
Small White 

Green-veined White ovum,  DHardiman
Green-veined white

Brimstone ovum,  DHardiman
         Brimstone 


Wood White

Orange Tip ovum,  DHardiman
Orange tip


 Orange Tip ovum
 


Orange Tip prior to 
 hatching

 

Lycaenidae

Small Blue ovum,  DHardiman
Small Blue 
ova

Small Blue ovum,  DHardiman
Small Blue 
ovum

Holly Blue ovum,  DHardiman
Holly Blue 
ovum


.
Small Copper
     ovum

Brown Hairstreak ovum,  DHardiman
Brown Hairstreak 
ovum

Brown Hairstreak ovum,  DHardiman
Brown Hairstreak 
ovum


PurpleHairstreak
Ovum


PurpleHairstreak
Ovum


  PurpleHairstreak
          Ovum

 

Nymphalidae

Red Admiral ovum,  DHardiman
Red Admiral ovum
on nettle leaf


Red Admiral ovum
on nettle leaf

Painted Lady ovum
Painted Lady ovum
.

Dark Green Fritillary ovum,  DHardiman
 Dark Green Fritillary
ovum

Dark Green Fritillary ovum,  DHardiman
 Dark Green Fritillary
prior to hatching


Marsh Fritillary ova  changing colour


Marsh Fritillary ova
 


Comma ovum
 


Comma ovum on nettle leaf

 

Satyridae

Wall Brown ovum
Wall Brown ovum


Speckled Wood 
ovum


Speckled Wood 
ovum


Speckled Wood 
ovum

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