The Hawaiian Islands have allowed insects to evolve unique habits, because the islands are isolated and originally lacked predators, such as ants and wasps. Ambush carnivorous caterpillars (_Eupithecia_ spp.; Lepidoptera: Geometridae) provide a remarkable example of a feeding behaviour unique to the Hawaiian Islands. Their prey includes various arthropods species. _Eupithecia_ larvae even attack predatory arthropods such as parasitoids. However, it is unclear whether _Eupithecia_ can attack ants. Here, I examined whether _Eupithecia orichloris_ can attack the invasive ant _Pheidole megacephala_ under laboratory conditions. _Eupithecia orichloris_ could successfully attack the minor worker of _P. megacephala_. However, the major worker of _P. megacephala_ counterattacked.&#xd;&#xa

Shinji Sugiura

English

AbstractThe Hawaiian Islands have allowed insects to evolve unique habits, because the islands are isolated and originally lacked predators, such as ants and wasps. Ambush carnivorous caterpillars (Eupithecia spp.; Lepidoptera: Geometridae) provide a remarkable example of a feeding behaviour unique to the Hawaiian Islands. Their prey includes various arthropods species. Eupithecia larvae even attack predatory arthropods such as parasitoids. However, it is unclear whether Eupithecia can attack ants. Here, I examined whether Eupithecia orichloris can attack the invasive ant Pheidole megacephala under laboratory conditions. Eupithecia orichloris could successfully attack the minor worker of P. megacephala. However, the major worker of P. megacephala counterattacked.</jats:p

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Can Hawaiian carnivorous caterpillars attack invasive ants or vice versa?

 1 
Can Hawaiian carnivorous caterpillars attack invasive ants or vice versa? 
 
Shinji Sugiura1,2 
 
1Department of Forest Entomology, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, 
Ibaraki 305-8687, Japan 
2Center for Conservation Research and Training, Pacific Biosciences Research Center, University of Hawaii, 3050 
Maile Way, Gilmore 408, Honolulu, HI 96822, USA 
E-mail: ssugiura@affrc.go.jp 
 
 
The Hawaiian Islands have allowed insects to evolve 
unique habits, such as ambush predating in caterpillars1 
and ground-dwelling in damselfly nymphs2, because the 
islands are isolated and originally lacked predators, such 
as ants and wasps3. However, many exotic species have 
been introduced to the islands through human activities, 
which has affected the native fauna3. 
Ambush carnivorous caterpillars (Eupithecia spp.; 
Lepidoptera: Geometridae) provide a remarkable 
example of a feeding behaviour unique to the Hawaiian 
Islands1,4. More than 20 endemic species of Eupithecia 
have been recorded from the Hawaiian Islands1,4. While 
the larvae of two Eupithecia species are herbivores, the 
larvae of other species on the islands are obligate 
predators1,4. The larvae of carnivorous Eupithecia perch 
inconspicuously along leaf edges (Fig. 1a) and stems and 
seize arthropods that touch their posterior body section1. 
Their prey includes various arthropods species, such as 
springtails, drosophilid flies, cockroaches, crickets, 
psocids, moths, and leafhoppers1,4. Eupithecia larvae 
even attack predatory arthropods. For example, 
Montgomery4 reported that Eupithecia orichloris 
(Meyrick) preyed on a braconid parasitoid. Although 
phytophagous Eupithecia are frequently parasitised by 
parasitic wasps and flies, the carnivorous species of 
Eupithecia are rarely parasitised, suggesting that 
carnivorous Eupithecia counterattack the parasitoids4,5. 
However, spiders may defend against Eupithecia attacks; 
one spider, Theridion grallator Simon, was attacked by 
E. orichloris, but the spider escaped from the E. 
orichloris by biting it4. Similarly, ants with strong 
mandibles may counterattack Eupithecia larvae4. 
However, it is unclear whether Eupithecia can attack 
ants. 
Here, I examined whether E. orichloris can attack ants 
under laboratory conditions (21°C). An E. orichloris 
larva (body length, 19.3 mm) and workers of the invasive 
ant Pheidole megacephala (Fabricius) collected from 
Oahu Island in early June 2010 were used for the 
experiment. Pheidole megacephala has minor (body 
length 2 mm) and major (3.5 mm) forms of workers; 
major workers have larger heads with stronger mandibles 
than minor ones6. First, I used forceps to place a minor 
worker of P. megacephala on a leaf where E. orichloris  
 
 
 
Figure 1. a An Eupithecia orichloris larva perching on a leaf; b E. orichloris feeding on a minor worker of Pheidole 
megacephala; c The body of the minor worker was torn apart in the E. orichloris attack (the arrow indicates the 
removed abdomen); d E. orichloris was counterattacked by a major worker of P. megacephala (the arrow indicates the 
biting by P. megacephala); e The major worker escaped from the E. orichloris attack; f E. orichloris lost a foreleg as a 
result of the bite by the major worker (arrow).
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perched. The E. orichloris was observed to bend the 
seized the ant the instant the ant touched its posterior 
body. The caterpillar seized the ant using its thoracic 
(elongated spiny) legs (Fig. 1b), and then used its 
mandibles to tear the ant body in two (Fig. 1c). Thus, E. 
orichloris can successfully attack the minor workers of 
P. megacephala. The next day, I similarly placed a major 
worker of P. megacephala on a leaf where E. orichloris 
perched. The E. orichloris was also observed to attack 
the ant the instant the ant touched its posterior end. 
However, the ant counterattacked (Fig. 1d) and was 
observed to bite one of the thoracic legs of E. orichloris 
(Fig. 1d) and ultimately escaped (Fig. 1e). The E. 
orichloris lost a foreleg and consequently lost its ability 
to seize prey (Fig. 1f). The caterpillar died 10 days later. 
The Hawaiian Islands, which originally lacked ants, 
have recently been invaded by many exotic ant species7. 
The invasion of native vegetation by exotic ants has 
reduced the abundance of endemic arthropods8. For 
example, the invasive ants Linepithema humile (Mayr), 
Anoplolepis gracilipes (F. Smith), and P. megacephala 
have gradually been invading native forests where 
Eupithecia caterpillars are found. Although it remains 
unclear whether the invasive ants have reduced the 
population of Eupithecia caterpillars, my simple 
experiment suggests that the invasive ant 
P. megacephala may affect Eupithecia caterpillars. 
 
ACKNOWLEDGEMENTS. I thank Vincent Costello 
and Brenden Holland for providing the caterpillar. The 
author was supported by a JSPS Postdoctoral Fellowship 
for Research Abroad. 
 
REFERENCES 
1. Montgomery, S. L. GeoJournal 7, 549–556 (1983).  
2. Zimmerman, E. C. Insects of Hawaii vol. 2: 
Apterygota to Thysanoptera, University of Hawai‘i 
Press (1948). 
3. Ziegler, A. C. Hawaiian Natural History, Ecology, 
and Evolution, University of Hawai‘i Press (2002). 
4. Montgomery, S. L. Carnivorous caterpillars: the 
systematics, behavior, biogeography and 
conservation of Eupithecia Curtis (Lepidoptera: 
Geometridae) in the Hawaiian Islands, Ph.D. 
Dissertation, University of Hawaii (1984). 
5. Henneman, M. L. and Memmott, J. Science 293, 
1314–1316 (2001). 
6. Wetterer, J. K. Pacific Science 61, 4437-456 (2007) 
7. Krushelnycky, P. D., Loope, L. L. and Reimer, N. J. 
Proc. Entomol. Soc. 37, 1–25 (2005) 
8. Cole, F. R., Medeiros, A. C., Loope, L. L. and Zuehlke, 
W. W. Ecology 73, 1313–1322 (1992). 
 
 
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Carnivorous caterpillars: the systematics, behavior, biogeography and conservation of Eupithecia Curtis (Lepidoptera: Geometridae) in the Hawaiian Islands,

GeoJournal 7, 549–556

Hawaiian Natural History, Ecology,

N a t u r e P r e c e d i n g s : d o i : .

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Can Hawaiian carnivorous caterpillars attack invasive ants or vice versa?

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