1921 .] 
Natural-history Notes. 
203 
NATURAL-HISTORY NOTES. 
On the Larval Habits of the Ant-lion ( Myrmeleon acutus Walker), by 
H. Hamilton, Dominion Museum. 
In January last, when camping at Rangataua, on the slopes of Mount 
Ruapehu, I had exceptional opportunities for studying the larvae of the 
ant-lion (Myrmeleon acutus). In the vicinity of our camp, on the banks 
of a stream flowing down from the mountain, were many colonies of the 
larvae in all stages of development. Although my observations were 
limited by a holiday of ten days’ duration, and consequently were not as 
complete as possible, I feel that what I observed should be placed on 
record. Little has been published on the habits of the New Zealand 
species. 
With regard to the situation of these colonies, it seems essential that 
they be established where the soil is dry and sandy. Overhanging banks 
of rivers and creeks above flood-level are generally chosen, while a sunny 
aspect seems desirable. The pitfalls or traps constructed by the larvae 
vary in size according to the development of the individual, and possibly 
also with respect to the composition of the surface soil. The angle of rest 
of the material composing the trap may be variable. In size the traps 
range down from 2 in. in diameter, and the deepest hole measured was 1J in. 
On several occasions I was fortunate in seeing the actual making of these 
pitfalls. After searching a colony for larvae I made it a practice to care¬ 
fully smooth out the ground and come back after dark. Apparently all 
the excavating-work is done under the cover of darkness. It was then that 
I was treated to a lesson in mechanical engineering. On deciding to con¬ 
struct a new trap, the larva, having selected the site, comes to the surface 
of the ground from below and commences operations. Progression or, 
strictly speaking, movement is always backwards, and the larva even at 
night traverses the ground under cover of a thin layer of soil or sand. The 
site having been finally selected, the worker proceeds to traverse in an anti¬ 
clockwise direction the outer perimeter of the intended trap, finally reach¬ 
ing the original starting-point. This traverse is attended by a scooping or 
shovelling action by the head of the larva, assistance being rendered in 
gathering the debris by the fore legs. 
The material gathered on the head is jerked to some distance, falling 
outside the boundary of the trap. After one circuit is completed in this 
manner the larva starts again on another round just inside the first circle, 
practically in the form of a decreasing spiral. The scooping action is 
continued, and soon the surface is lowered by one terrace. By repeating 
the whole process in a circle of smaller diameter another layer is ejected. 
Finally, after about four rounds, the trap is in the form of an inverted cone. 
When satisfactorily finished, the larva takes up a position at the bottom 
of the pitfall, buried in the sand, yet with its formidable jaws ready for 
instant action. I found the food of the larvae to be very general. Ants, 
flies, wetas. wood-lice, and spiders are all relished for their juices, which 
are extracted by the larva without relaxing its jaws. 
When fully fed the larva spins a globular silk cocoon about \ in. in 
diameter, covered on the outside with particles of sand. In this it pupates, 
and finally emerges from a small circular opening through which the pu'pal 
skin remains protruding. 
