Care Sheet - Giant Thorny Devil Stick Insect (Eurycantha horrida)

Written by: Richard’s Inverts

*A bundle of Giant Thorny Devil Stick Insects (Eurycantha horrida). This is the typical congregation behaviour that Eurycantha spp. exhibit during the day.*

Common Name: Giant Throny Devil Stick Insect
Scientific Name: Eurycantha horrida
Distribution: Popondetta, Papua New Guinea

Scientific Classification:
Order: Phasmatodea
Family: Lonchodidae
Genus: Eurycantha (Boisduval, 1835)
Species: horrida (Boisduval, 1835)

Etymology:
[horrida] meaning “with many prickles” in Latin

Size (body length): Females – 17-19 cm, Males – 14-16 cm
Foodplants (full list further down): bramble, oak, beech, etc.

Temperature: Room temperature (18-25°C)
Humidity: 70-80% RH
Enclosure size: LxWxH: 40x40x60 cm

Temperature: Room temperature (18-25°C)
Incubation length: 4-6 months

*The gigantic femoral spine of a male Giant Thorny Devil Stick Insects (Eurycantha horrida).*

Species Description:

Eurycantha horrida is the legendary species of stick insect that was the un-obtainable, holy grail for every stick insect enthusiast for the past few decades. Recently collected in Popondetta (city in Papua New Guinea) in 2021 and distributed to breeders in 2022/2023, this species is quickly becoming established and a favourite in European cultures.

E. horrida is currently the largest Eurycantha species available in the hobby. Females of this species are gigantic, reaching an average of a whopping 18 cm from head to tail. Males are a little shorter in length, but make up for it with impressive +1cm spines on their hind-legs. Their thorax and abdomen are lined with numerous spikes. More-so than other Eurcyantha species.

Key Rearing Notes:

Eurycantha horrida is a very long-lived species where individuals can live for 12+ months once adult.
The males of this species are very large and strong. As nymphs, they tend to docile but once they reach adult and are in the presence of female pheromones, they can become very aggressive towards other rival males.

Female Description:

Females are large, spiny and thick bodied.
Females can reach 17-19 cm once fully grown.
Females are not winged.
Like other Phasmatodea species that dig and lay eggs into substrate, the females develop shovel-like tips at the end of their abdomen as they grow older.

Male Description:

Males are large, spiny, and quite thick bodied.
Males can reach 14-16 cm once fully grown.
Males are not winged.
Key characteristic of the males of this species is that they possess an incredibly long spine on the femur of their hindlegs.

*The numerous spines that adorn the body of the Giant Thorny Devil Stick Insect (Eurycantha horrida) gives it their scientific name.*

Foodplants:

Eurycantha horrida is a polyphagous species, meaning that this species can accept a wide range of foodplants and are not limited to a single species of foodplant. Therefore, E. horrida is relatively easy to rear as most people will have access to at least one of the tested foodplants below.

Here is a list of foodplants that Eurycantha horrida accepts:

Rubus spp. (bramble, raspberry, etc.) - accepted at all stages
Rosa spp. (rosa) - tested only on adults
Quercus spp. (oak) - accepted at all stages
Fagus spp. (beech) - accepted at all stages
Castanea spp. (sweet chestnut) - accepted at all stages
Corylus spp. (hazel) - tested only on adults
Platanus spp. (plane) - tested on large nymphs and adults
Gaultheria shallon (salal) - accepted at all stages
*Eurycantha horrida also accepts treats of apple slices occasionally. Please note that while offering fruits may potentially be beneficial to them by being a source of extra vitamins and minerals, it should not be used as a substitute for their foodplants.

Foodplants should be offered for Eurycantha calcarata in the same way as most other stick insect species. The plant should be offered via stem cuttings that ideally run the span of the enclosure height, and not individual leaves/cluster of leaves on the floor. As stick insects have evolved to be almost exclusively arboreal for most of their lives (examples when this is not true is when females of egg-burying species descent to the forest floor to lay eggs), foodplants reaching the top of the enclosure is very important so that they can find it. This is because the eye-sight of stick insects is relatively poor and to find food, they rely on chemical cues that they pick-up using their antennae and mouthparts when coming into direct contact with the leaves.

To prolong the freshness of these cut foodplant stems, the stems can be placed in water containers such as jars and pots, much like how cut flowers are placed in vases so that they last longer. The opening of these jars should be blocked off with material such as a wad of kitchen paper to prevent nymphs crawling into the water and drowning (stick insects are unfortunately not the brightest of creatures). The water in these jars should ideally be changed twice a week to maintain the freshness of the foodplants.

*An adult male Giant Thorny Devil Stick Insect (Eurycantha horrida).*

Enclosure Size:

As this is a large species, a large enclosure is necessary to provide enough height for safe moulting. Similar to keeping praying mantids, a recommended minimum enclosure size is 3x the body length in height, and 2x the body length in length and width. As the body length of fully grown adult females of Eurycantha horrida can reach near 18 cm, the minimum recommended enclosure size is 40x40x60 cm (LxWxH).

Temperature:

Eurycantha horrida can be raised at room temperature (18-25°C), so no extra heating is necessary unless your room drops below 18°C in the winter months. Upwards of 28°C may be tolerated for short periods, but please note that this can potentially increase the chances of health conditions that can increase the mortality rate.

Humidity:

A relative humidity of 70-80% is recommended for Eurycantha horrida. Unlike other, more commonly kept Eurycantha species, E. horrida appreciates slightly higher humidity. Lower humidity can be tolerated for short periods, but this can be detrimental especially during their final adult moult as they can get stuck in their old skin easier. Humidity can be maintained via evaporation from substrate on the floor of the enclosure, or via a light-medium spray once every few days. When spraying, it is imperative that there is still enough airflow in the enclosure for the water to evaporate after several hours so that the enclosure/foodplant/insects do not stay wet for prolonged periods of time.

*A freshly moulted adult female Giant Thorny Devil Stick Insect (Eurycantha horrida). This female measured just under 18 cm and was one of the larger specimens in my colony, but not the largest.*

Behaviour:

Both nymphs and adults of Eurycantha horrida become active and feed in the dark once night falls. At dawn, their activity slows down and they congregate in groups in the corners and edges of their enclosure, where they will remain motionless until dusk falls again.

The males of this species can be very territorial (especially once adult and in the presence of breeding females) and aggressive if provoked. Their defensive stance is to stand on their front and middle legs while they lift their abdomen and hind legs up in the air. Any object that comes within reach will be snapped at in a quick grabbing motion using their hind legs, with the aim of driving their long femoral spines into the rival/enemy. Due to this aggressive nature of males, they should ideally be kept in smaller groups once adult.

Eggs and Nymphs:

Incubation time on average takes 4-6 months at ~22°C. The warmer the temperature, the shorter the incubation time. The cooler the temperature, the longer the incubation time. Take care not to incubate at temperatures higher than 26°C as too high of a temperature can literally cook the eggs. Please note that while most eggs have around the same incubation time, some can take significantly longer and can hatch months apart.

As Eurycantha horrida lays its eggs into substrate, the eggs can either be left in the enclosure to hatch in-situ or collected periodically (once every few weeks) to incubate in a more controlled environment. If removed, the eggs should be should be buried in a similar substrate, such as moss, coco-fibre, vermiculite or sand.