Dolichopodidae

The Dolichopodidae are a large family of flies with over 7000 species described wordwide. They are commonly known as Longlegged flies, unsurprisingly due to their very long legs!

This image is a stack of nearly 200 separate shots, taken with a Nikon Nikon N plan 10/0.30 objective.




The image seen below is a crop of the image above, it clearly shows the hexagonal ommatidia. Insect eyes function quite differently from our own and they produce an image which lacks detail. The main function of the insect eye is not to produce an image, but to detect movement. Ommatidia are well adapted to this function, they only detect light that passes through a very narrow angle. This means that any movement of an object in front of the eyes is easily detected through a change in the pattern of light detection in the many ommatidia across the eye surface.
What looks a little like a pupil in each ommatidium is just a reflection of the microscope objective.

Nettle sting

Stinging nettles, Urtica dioica are very interesting but often very annoying plants, they seem to grow best along side paths just where there they are most troublesome, the slightest brush against the plant leaves you with a prickly rash. At least I am glad we do not have the nettle Urtica ferox which grows in New Zealand its stings have been known to kill dogs, horses and even a human!

The photo shows a section of nettle stem with lots of non stinging hairs and two stinging hairs called trichomes, the stinger on the left frame I don't think is fully developed, it does not have the enlarged base which the trichome on the right has. The plant was only about 5cm tall so it was very young, the stem is just over 1mm thick. The base of the sting is a reservoir containing the cocktail of chemicals which result in the irritation and rash from of a nettle sting, acetylcholine, serotonin, histamine, leukotrienes, moroidin and 5-hydroxytryptamine.

The hollow, silica trichomes have tiny protective tip, it is just about visible in the photo. This tip breaks of easily when touched transforming the hair into a sharp needle that can easily break through skin to inject its toxins.

Oak bush-cricket 'ear'

Insects do not have ears on their heads as mammals do, but the detection of vibrations and sound reception is very important to insects. By using a variety of organs many insects are able to detect a wide range of sound frequencies, far greater than our human ears can, the most elaborate of these organs is the tympanum.

A tympanum comprises of a section of flexible membrane, air sacs which evolved as modifications of the trachea and sensory cells. Several, quite distantly related insect group use this type of sensory organ suggesting that tympanal hearing has evolved independently on several different occasions. In bush crickets, tympanal organs are found on the foretibia, whereas in grasshoppers they are located on the hind legs, in some moth species tympana are found at the base of the wings.


For the species shown in the photo, Meconema thalassinum hearing is particularly important during courtship where males stridulate by tapping their hind tarsi on vegetation (this is fairly unusual for bush crickets, most rub their forewings together), this produces a very quiet drumming sound which attracts females.