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Stick Insects finding Mate
Stick Insects are heavily camouflage, how do they find their mate for reproduction?Most insects have their special ways for finding their mate for reproduction. To name a few, the butterflies and dragonflies have very good eye sight, so they attract their mates by colours and patterns. The crickets and cicadas sing their love songs. The moths use their sense of smell. The ants have their mating flight while some butterflies have gathering on the hill top. For Stick Insects, it seems that they do not have any special methods to find their mates. They have poor eye sight as well as heavily camouflage, so it is not easy for them to 'look' for their mates. They do not produce any love songs, their antenna is not well developed as moths to smell their mates. They do not have special gathering event like ants of butterflies. How do Stick Insects find their mate? This seem the job of the male stick insect, because usually only the male can fly. How do the males locate a female? In most stick insect species, females are much larger than males in size. However, males' antenna are always longer than females'. This give a clue that female stick insects probably attract males by pheromones. In 1996 newspaper, Australian Museum naturalist Dr. Andrew Parker discovered that Spiny Stick Insect Extatosoma tiaratum reflect ultraviolet light to attract male. For a frog species in the desert, because it is very difficult to find a mate, if a male frog meet a female frog, even not in the mating season, the male will hold itself on the back of the female frog until mating season. We saw some male stick insects doing the same thing. Its seem that the stick insect employ the same method as the desert frogs. I read form books that some stick insect species can breed
parthenogentically, i.e., reproduce by female without mating. The eggs will
hatch without fertilized by males. Surprisingly, the unfertilized eggs produce
both males and females (this contradicts with my knowledge of chromosomes
reproduction). This could be a evolution solution that temporally fix
this problem. Tessellated Phasmatids are usually living on the top of the trees, why we can find them near the ground?Female Tessellated Phasmatids vary in colour from brown to pale green. They should live high on the tree, but we found them all near the ground, either in the bush or on the tree trunk. When we bring them home, they all lay eggs in the first day. We read the reference books that stick insects are usually living on the top to the tree. After storm some of them may fall to the ground so that we can occasionally find them near the ground. Especially for the female stick insects, there seem no other reasons that they should leave the tree top and go down to the ground. From our experience, we found five female Tessellated Phasmatid during summer season in 2001. Two of them are found in the lower plants under large gum trees. Three of them are resting on the trunk of trees and trying to climb back to the top. Only one female stick insect we found was two days after heavy rainfall. All the others were found without any bad weather. (Since in Brisbane we usually have good weather, bad weather days are easily remember.) It seems that they are not fall to the ground because of bad weather. We had taken four of them back home to study. All four female stick insects lay some eggs during we keep them. Some of them die within a few days. So I think the stick insects were not fall down due to bad weather, they went down to some good locations to lay their eggs. To prove that we should try to find out what is the favorable site for stick insects to lay their eggs. Those sites could be the wet soil with young trees and new plants. We should try to find out that the Tessellated Phasmatid in the wild will come down and look for a place for laying eggs, instead of just dropping their eggs from the tree. Go down from the tree may increase their chance of being prey, it could be worth to do that if this increase the hatching chance of their offspring. This may not decrease their fitness too much for they will die after laying eggs anyway. This can also explain why we seldom see the nymph Tessellated
Phasmatid in the wild, for they no need to take the risk to come down. Why the Titan Stick Insects are so big?Stick insects are large in size in general. One reason is they mimic a stick to hide away from their predators, usually birds or some other larger sized vertebrae animal. The camouflage will only effective to cheat larger predators. To smaller size predators such as spiders and praying mantis, sticks insect may not look like a stick. One of the solution to avoid those smaller predators is larger in size. This also explained why some stick insect mimic ants and not stick when they are in small larva stages. For Titan Stick Insects, there may be many factors make them the longest insects. I notice one major factor which is theirs hugeness resemble the size of the stick on the tree that they feed on. They feed on the cypress trees. For those trees, beside some main trunks, most of the branches are about the size of the Titan's body. There are many branches in high density. If a twig fall from the top part of the tree, it usually hangs in the middle of the trees. When I look up from the bottom, I saw high density branches, live of dead, close together. There could be many Titan or none, very hard to tell. Titans mimic the size as well as the shade of the branches. Back to Top
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