Stick Insects L227 December 2002 December 2002 December L227 Stick Insects Stick SCHOOL SCIENCE SERVICE L227 Stick Insects Contents 1. Scope of this guide…………………………………………………………………………….. 1 2. Introduction……………………………………………………………………………………... 1 3. Some basic information about stick insects (Phasmids)…………………………………... 1 3.1 The external anatomy of phasmids………………………………………………… 1 4. The life history of stick insects……………………………………………………………….. 4 4.1 Eggs…………………………………………………………………………………… 4 4.2 Nymphs……………………………………………………………………………….. 5 5. Phasmids suitable for schools………………………………………………………………... 6 6. Housing requirements…………………………………………………………………………. 11 6.1 Eggs…………………………………………………………………………………… 11 6.2 Nymphs……………………………………………………………………………….. 11 6.3 Adults………………………………………………………………………………….. 12 7. Feeding…………………………………………………………………………………………. 15 8. General care……………………………………………………………………………………. 16 9. Handling………………………………………………………………………………………… 16 10. Surplus stock…………………………………………………………………………………… 17 11. Holiday care……………………………………………………………………………………. 18 12. Transporting stock for sale or exchange……………………………………………………. 18 13. Diseases………………………………………………………………………………………... 19 14. Educational uses of stick insects…………………………………………………………….. 19 14.1 Studying insect life cycles................................................................................. 19 14.2 Studying insect anatomy.................................................................................. 19 14.3 Investigating stick insect movement................................................................. 20 14.4 Investigating stick insect physiology................................................................. 20 14.5 Investigating stick insect behaviour.................................................................. 21 15. Appendix 1 Checklist of equipment for keeping stick insects………………………….… 24 16. Appendix 2 Suppliers of livestock and equipment…………………………………..…….. 25 17. Appendix 3 Sources of help and advice….………………………………………….……... 29 18. Appendix 4 Publications……………………………………………………………….……... 30 19. Appendix 5 A d-i-y cage for stick insects…………………………………………………... 32 20. Appendix 6 Web sites dedicated to stick insects………………………………………….. 35 Strictly Confidential Circulate to members and associates only As with all CLEAPSS materials, members and associates are free to copy all or part of this guide for use in their own establishments. CLEAPSS School Science Service Brunel University Uxbridge UB8 3PH Tel: 01895 251496 Fax: 01895 814372 E-mail: [email protected] © CLEAPSS 2002 Web site: www.cleapss.org.uk L227 Stick Insects 1. Scope of this guide This guide provides information about choosing stick insects suitable for study in schools and advice on how to maintain them in good health. It is intended for teachers and other staff with little previous experience of keeping insects. Details of suppliers of insects and equipment are given, together with a bibliography of publications dealing with their breeding and care. Some suggestions for practical work involving stick insects are also included. 2. Introduction Most children (and many adults!) are fascinated by stick insects. Their relatively large size and ability to mimic the plants on which they live are unique in the insect world. Despite these unusual features, they possess all the characteristics of typical insects, making them ideal for study in schools. They have the additional advantages of being straightforward to maintain, easy to breed and relatively free from any significant health hazards. The majority of species are generally harmless to both people and crops but a few types can nip, bite or scratch. One species, the Florida walking stick, Anisomorpha buprestoides, can re- lease a defensive spray that is irritating to the eyes. A recent report suggested that people coming into extended and frequent contact with the insects may develop an allergic response to the dust produced by their skins and frass. The validity and significance of this claim has yet to be assessed. Although it is illegal in the UK to release any non-indigenous creature into the wild, if any stick insects do escape, they rarely survive for long enough to cause serious problems. Nevertheless, care should be taken to ensure that no escapees gain access to a heated greenhouse, since infestations have sometimes been rep- orted in these circumstances. 3. Some basic information about stick insects (Phasmids) Stick and leaf insects belong to the insect order Phasmida, a group that includes about 2,500 species. They are relatively large, nocturnal, tropical or subtropical leaf-eating insects, the adults ranging in length from 20 mm to 300 mm. Their closest relatives are cockroaches and mantids. The name phasmid derives from the Greek word phasma, meaning spectre or ghost (from the way these insects blend into their background). Their ability to mimic plant organs is legendary. Adult insects resemble twigs or leaves and their eggs are strikingly similar in appearance to seeds (although whether this is likely to help their survival is not clear!). Their camouflage extends beyond mere physical similarity since they often also behave like plant organs, remaining immobile for long periods or sway- ing in the breeze, mimicking the movement of vegetation. 3.1 The external anatomy of phasmids Despite the unusual body forms shown by some stick insects, they display all the basic characteristics of the major group – the Arthropods – to which they belong. All have a tough outer skin, composed of the protein chitin that protects the body from drying out and acts as a skeleton. This external skeleton (the exoskeleton) supports and protects the body and forms a system of levers on which the 1 muscles act to cause movement. Much of the success of the arthropods can be attributed to this exoskeleton, since it has enabled members of the group to live and move on dry land, water and in the air. Its properties are also important in determining the maximum size, strength and method of growth of members of the group. The body form of phasmids varies widely. Stick insects have elongated cylin- drical bodies, although some have leaf-like side projections; the closely-related leaf insects have flattened bodies and limbs. In many species, the surface bears spines or more flattened projections that contribute to the camouflaged appear- ance of the insect. The following illustration shows the main external features exhibited by most phasmids. The external features of a stick insect The head The head bears a pair of simple, filament-like antennae, which in some cases can be quite long. Males usually have longer antennae than females. All stick insects have a pair of compound eyes, while those types that fly may have two or three simple eyes in addition. The mouthparts are forward facing and designed to bite off pieces of leaf. They consist of an upper lip (the labrum), a lower lip (labium), a pair of jaws (mandibles) to chop the food and a pair of secondary jaws (maxillae). The labium and maxillae bear sensory palps to taste the food and move it towards the mouth. These structures are shown in the following diagrams. 2 A stick insect head viewed from below Maxillary palp Mandible Labial palp Eye Labium A stick insect head viewed from the left side Simple eye Antenna Compound eye Neck Labrum Labium Mandible Maxilla Labial palp Maxillary palp The thorax The thorax has three segments called (from the head end) the prothorax, meso- thorax and metathorax. Each bears a similar pair of legs, although the rear pair may be somewhat larger and stronger. The end section of each leg consists of five parts called tarsi (singular – tarsus). A typical stick insect limb Trochanter Femur Tibia Tarsus Claw The legs are relatively easily shed, a process referred to as autotomy. This mech- anism allows the insect to escape capture or entanglement with minimum dam- age, since a replacement limb grows and enlarges each time a moult occurs (see section 4). The tarsi of regenerated legs are 4- rather than 5-segmented. The mesothorax and metathorax each bear a pair of wings. However, the wings are reduced or lost in some species, especially the females. The fore wings and the front portion of the hind wings are modified to cover and protect the folded, flying part of the hind wings. Flying is possible in some species but is never strong and usually consists of a fluttering glide. The abdomen Despite appearances, there are eleven abdominal segments. The first or ‘median’ segment is closely linked to the metathorax, while the eleventh merely consists of a few projections attached to the last obvious abdominal segment. The ‘median’ segment is often important in classifying phasmids. 3 The external male organs appear as relatively small projections below segments 8 and 9. Females possess an ovipositor, a larger structure from which the eggs are pushed out. The ovipositor consists of appendages from the 8th and 9th segments concealed by a flap-like plate, the operculum, which is derived from the lower covering of the 8th segment. These differences in shape can be useful in determin- ing the gender of individual specimens. In both sexes, there is a pair of unsegmented appendages arising from the rear of the abdomen called the cerci (singular: cercus). These may be involved in the mating process (see below). 4. The life history of stick insects The life history of stick insects consists of three stages: egg, nymph and adult. 4.1 Eggs In some species, eggs are fertilised in the conventional manner by male insects that