| Gum Leaf Katydid - Caedicia sp.Family TETTIGONIIDAEThis page contains pictures and information about the Gum Leaf Katydids that we found in the Brisbane area, Queensland, Australia.
The KatydidAdult Gum Leaf Katydids are resemble gum leaf, both in shape and colour. Some adults may have some brown markings on their legs. Their front wings look exactly a gum leaf, with the thick white vein at the middle. The older nymph looks similar to adult except wingless and has brown patterns on its body and legs. The brown patterns are resembled the brown spots on the gum leaves. The young nymphs look quite different from their adults, instead they look like large brown ants.. Their brown colour gradually disappear when grow up. They feed on eucalypt tree leafs. Like most of other katydids, they do not cause much, if any, economic damage.
Their rear pair of legs are longer and stronger than the front and mid pair of legs, but they look thinner than the hind legs of grasshoppers. We seldom saw them jump. Instead, they kick with their spiny hind legs if disturbed. All their legs are armed with spins.
Their compound eyes are relatively small, with poor eye sight. Their simple eyes can hardly be seen. From the response shown by their antennae, they can see my hand within 30cm. But they seems cannot distinguish my hand from a branch of leaf. Their antennae are located on the head in front of the compound eyes. The antennae are segmented and are used as organs of smell and touch. They have strong chewing mouthparts for eating the gum tree leafs, which is very tough to our standard. Laying Eggs
Because they lay eggs on plants and their eggs look like plants materials, katydids are sometimes distributed by nursery stock.
From Nymph to AdultWe found a Gum Leaf Katydid nymph on a gum tree in early winter. At that time we did not know they are the Gum Leaf Katydid. We wanted to know what would they be when they grow up. We take them home and watch them grow. We put them openly on a few branches of gum tree leafs, held in a water bottle. We replaced with flash branches every week. The next week We found another nymph and we put them together. Both of them were found on the same type of gum tree and they were sitting on leafs about one meter above the ground. They did not eat much, less than a leaf per day. We sprinkle water on the leaves twice a day. The insects moved and hided under leaves to avoid getting wet, then came up and drank the water. After few weeks later, with about two or three times of moulting, we saw that one katydid nymph was male and the other female. It is not too difficult to tell, female has the distinctive ovipositor for laying eggs which the male does not have. The two katydids seem like to eat the leafs on the tips of the branch. They will eat about 1/8 to 1/4 of the leaf per day. Sometime they choose only brown part of the leaf to eat. They do not eat much, spend most of the time sitting on a leaf.
We can find the adults and nymphs of different stages throughout the year in Brisbane. The Gum Leaf Katydid does not have seasonal growing cycle. This is different from the Giant Grasshoppers, they have the one year growing cycle and we will see only adults in winter. The First Instars
Their Love SongKatydids and crickets are the major noise source in the field at night. The male produce sound, known as stridulation, to call for the female. They usually sing for the whole night. Both female and male have their hearing organs on their front pair of legs. Gum Leaf Katydid produce the sound by rubbing their two front pair of wings, or tegmen, together. There are the raised vein on the underside of both tegmen. By rubbing them together, just like rubbing the teeth of two combs against each other. The male katydid that we keep sings not very often, about two to five times from evening to twelve o'clock before we sleep. Every time is just three 'did-did-did' sounds, and never sing when I come close. So I do not have the sound record, like what we have done for the Mole Cricket.
Different species produce different pattern and different frequency of stridulation. This is the common way of katydids and crickets making the sound. However, the Mole Crickets produce the sound in the different way. Typical Insect Leg
Let's have a closer look of the katydid front leg. The drawing shows the foreleg of the katydid, which is the typical example of insect legs except there is the special organ tympana. The tympana is only found on katydids' and crickets' forelegs, and not on other legs nor on any legs of other insects. All insects have three pairs of legs. These legs can be variously modified depending on the type of insect. Basically each leg has 6 segments. The coxa connects the leg to the thorax. Leading outward are the segments: trochanter, femur, tibia, and tarsus. The tarsus comprised of 3-5 very small segments. At the end of the last tiny segment is the claw. There are usually spines on the tibia. The tarsomere on the tarsus is the part in contact with the ground. For more information on insect body parts, please see the Insect Scientific Page.
CamouflageWe found that they usually active at night. Actually their 'active' in not really active. They feed on leaf and walk around within a small area. In day time they usually stand still on a leaf near the tips of the branch. Usually it will take us minutes to find them although we know where to look for them. Gum Leaf Katydid like to hide on the tips of the branch, but not on the top of the tree. This may help them to avoid the predation from birds. This also explain why we can find them easier than those species hiding on the tree top. We notice a interesting way of the Gum Leaf Katydids handling their droppings. Most insects, such as the Giant Grasshoppers, just let their droppings drop vertically onto the ground, or the leave just under them. So sometime we can use their droppings to locate them. For the Gum Leaf Katydids, we notice that every time, when their droppings are half way out,. they use their hind leg, left of right, to kick them far away. This will sure help them to hide away from the predators. This habit is somewhat similar to the Goliath Stick Insects. To see another way of dropping handling, please click here.
They always eat the shard skin after moulting. So that their predator cannot find them by their skin.
Questions for DiscussionWhy it is the male katydid who made the calling, and not the female?
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