There are more than 2,000 species of Stick Insect (known as ‘Walking Sticks’ in America) worldwide. Probably the best known of these is the Laboratory Stick Insect (Carausius morosus) which was introduced from India and has been cultured in Europe since nineteenth century. It is a popular pet with children.
Parthenogenetic Females
The individuals originally imported into Europe came from stocks which were ‘parthenogenetic’ – in other words the females can lay fertile eggs without any male assistance. (It seems that the ‘eggs’ develop in such a way that they make the equivalent of true eggs and sperm which can then join together to produce a true egg.) Small males are sometimes found in these captive populations, but they are extremely rare, maybe one male to every thousand females.
Males
Some populations of Carausius morosus which still live in the wild in India seem to breed in a conventional fashion. Here the males are much more common and they are fully involved in the process of reproduction. There are probably good genetic reasons for this since without normal sexual reproduction the species would be expected to lose genetic diversity over time and therefore be unable to adapt and evolve.
Populations of Introduced Laboratory Stick Insects
Escaped ‘pet’ stick insects have become established in Europe and America, and when the climate is favourable they seem to do well. This could become a problem since they can eat a large variety of plant leaves (favouring Privet, Ivy, Hawthorn, Bramble, Rose and Lettuce). Eating crop plants could easily elevate them to ‘pest status’ in regions where escaped populations survive well, and without natural enemies and diseases this could become serious.
Disposal of Stick Insect ‘Waste’
In order to reduce the possibility of further unwanted introductions into the wild it is a good idea to think carefully about what you do with the waste when you clean out a stick insect cage. You need to make sure that there are no viable eggs, young larvae or adults mixed in with it. This is not as easy as it might sound, since these insects are extremely well camouflaged. The young and adults look remarkably like twigs and sticks, and the eggs bear an uncanny resemblance to Privet seeds. Bag the waste material and then either keep it in the freezer for a while or ‘zap’ it in the microwave. Either treatment will give stick insects and their eggs a very hard time and you can then safely dispose of the remaining stuff in the bag.
Short ‘YouTube’ video of a baby stick insect walking
Click on the image below to enlarge it.
Other articles by John Blatchford
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