Sunny Stick Insect (Sungaya Inexpectata)

The sunny stick insect (Sungaya inexpectata) is a phasmid species native to the Philippines and is one of the more common species in captivity. It is important to note that there are discrepancies regarding this species and their appearance, as there are actually two distinct populations. The first is the sexual population of Sungaya called Sungaya inexpectata "Ilanin Forest-highland," and the second is the parthenogenetic population called Sungaya inexpectata "Batangas-Lowland." This distinction between the populations was formally described and named in late 2023, with the "Ilanin Forest-highland" species now being described as Sungaya aeta. Despite this, the care requirements for both are very similar (excluding appearance and breeding). Therefore, throughout this care sheet, the terms "Sungaya" or "sunny stick insect" will be used as umbrella terms.

Nymphs: Newly hatched nymphs measure ~20mm in length and display light to dark brown colouration. Their distinctive patterns and colours do not emerge until after several moults. Nymphs have beige-yellowish eyes, small antennae, and a segmented abdomen. They typically mature to adulthood after ~4 months.

Adults: The sunny stick insect is a medium-sized phasmid. Adult females reach ~70-80mm in length, while males measure ~40-50mm. Females are noticeably larger than males, not only in length but also in body width, being approximately 2.5 times thicker.

The two species of Sungaya exhibit a vast range of patterns and colours. Their colouration spans from jet black to grey, light brown, caramel, orange, and mossy green (this is a rare green form), truly encompassing a broad spectrum. Patterns can include a white stripe down the back, indicative of the 'Lowland' form of the species. 'Highland' forms lack this stripe and are less patterned. Because the 'Highland' form reproduces through parthenogenesis, while the 'Lowland' form reproduces sexually, this sexual reproduction contributes to the wide range of colours and patterns observed in the ‘Lowland’ form.

Some individuals may have a brown stripe down their back, and most display a distinctive white stripe on each leg. Generally, males tend to have more subdued colouration and fewer patterns compared to females.

Both sexes possess antennae, but male antennae are longer, measuring about 30mm and reaching over half their body length. Females have a large, prominent ovipositor for laying eggs.

Males and females live for ~10-12 months but can live for longer than this.

The sunny stick insect, like most phasmids, is primarily nocturnal. Don't expect to see them actively moving or feeding during daylight hours; instead, they become more active and feed at night.

This species is known for its docile nature and is very easy to handle. However, when threatened, the sunny stick insect employs a clever defence mechanism: it plays dead, remaining motionless and mimicking a stick as convincingly as possible. When disturbed, they may also gently sway from side to side.

Sunny stick insects eat a variety of plant species including bramble, hawthorn, chestnut, raspberry, beech, and rose species. When selecting food plants, ensure they are free from insecticides or other harmful chemicals. Furthermore, before offering food to your phasmid, it's advisable to wash the cuttings with water to remove any surface debris and hitchhikers.

To maximise plant longevity and minimise maintenance, consider keeping the plant in a pot of water within the enclosure. However, take care to cover or reduce the size of the pot's opening to prevent the phasmids from accidentally falling in and drowning – particularly for nymphs, which are more prone to drowning.

Always provide a fresh source of food. On average, clean out the enclosure once a week, replacing old food with fresh offerings and adding new substrate to remove waste. This weekly maintenance is also an ideal time to collect any eggs that have been laid.

The sunny stick insect is an easy-care phasmid and therefore great for beginners.

Temperature: Maintain temperatures between 20°C to 25°C during the day. It’s acceptable for temperatures to drop to ~18°C at night. This species can be comfortably kept at room temperature without issue. Note that warmer temperatures will accelerate the insects development.

Humidity: This species prefers a medium to high level of humidity, ranging from ~60-80%. To maintain the appropriate humidity levels, mist the enclosure every day or every other day, focusing on the food plants rather than directly spraying the insects. This misting also provides water droplets for the sunny stick insect to drink.

Adequate moisture is crucial for successful moulting, which is essential for the insect's growth and development. Use dechlorinated water for misting to prevent potential harm. A substrate of paper towels or coir (coconut fibre) can help maintain higher humidity levels.

Lighting: Mimic natural day/night cycles using either natural or artificial lighting.

When housing sunny stick insects, the enclosure size should adhere to the general rule of thumb for phasmids and phyllium: at least 3 times the length of the insect's body in height, and at least 2 times the length of the insect's body in width. A minimum enclosure size of 30cm x 30cm x 45cm (width x length x height) is recommended. This size will be more than adequate for 2-3 adult pairs of sunny stick insects. Additional height is beneficial, as it provides ample space for the insects to hang vertically during moulting.

For this species the addition of bark is recommended at the bottom of the enclosure. The sunny stick insect likes to hide beneath this bark during the day. Cork bark is ideal for this purpose.

For young nymphs, it is recommended to employ a free-standing where the food plant does not touch the enclosure walls. This prevents nymphs from wandering off, hiding, and starving themselves.

Proper ventilation is equally important as maintaining high humidity. Ensure ample airflow to prevent stagnant conditions and mould developing. At a minimum, a mesh or netted roof is recommended. Netted material also provides easier grip for the insects, which is especially beneficial during moulting when they often hang from the ceiling.

As mentioned in the introduction, it's important to note that there are two distinct species of sunny stick insects. The 'Highland' form is exclusively female, reproducing via parthenogenesis. This process produces unfertilised eggs that hatch into genetic clones of the mother. The 'Lowland' form, on the other hand, reproduces sexually, requiring both male and female insects.

Breeding the 'Lowland' form is easy, as once they reach sexual maturity females and males will readily mate. You may observe males “piggy-backing” on females during this process.

There is conflicting information on the internet about the egg-laying behaviour of sunny stick insects. Some sources state that the eggs are just dropped to the floor by the female’s whip-like movement of her abdomen. However, others state the ova are deposited into soil by the female and therefore substrate should be provided (a depth of ~5cm). It appears that both of the above behaviours can occur, but the latter is more common. Therefore, it’s advised to provide a tub of substrate or sand on the enclosure floor to give females the option. If you don't provide this, females may exhibit pacing behaviour across the enclosure floor and will become unhappy.

The eggs are greyish-black in colour and ~6mm in length. These are relatively large eggs for this phasmids size. They have peculiar, circular, engraving-like indents. One end is nearly flat with a jet-black cap, while the other end has a small, hill-shaped hump that is also slightly darker than the rest of the egg.

Females lay groups of 10-12 eggs every two weeks. If eggs are laid in the substrate, they can be incubated there or removed and incubated on vermiculite/paper towels. The incubation period lasts ~4-6 months. Eggs should be kept under the same conditions as nymphs and adults, with temperatures of ~20-25°C and humidity of ~60-80%. Ensure they receive daily light exposure and regularly check for mould growth.

If you notice mould on an egg, carefully remove it from the container. You can attempt to gently wipe off the mould using a clean paper towel or soft brush. However, if the mould growth is extensive, it's best to discard the egg to protect the health of the others. If mould has developed, thoroughly clean the container housing the eggs. Pay particular attention to the substrate, especially if using paper towels. Vermiculite or coconut fibre substrates are less prone to mould growth.