92 



AN Insect-Catching Grass 



(Cenchrus australis, R. Br.). 



By Arthur M. Lea, F.E.S., Museum Entomologist. 

 [Contribution from the South Australian Museum.~\ 



[Read April 8, 1915.] 



Plate IX. 



In 1892 when on the Tweed River in New South Wales 

 I saw a large and powerful beetle, Lamprima aurata, strug- 

 gling on the seed-head of a grass, apparently without power 

 to escape. It was caught by a lind leg. The grass was 

 growing close to a small watercourse and in rather deep shade ; 

 on looking around many other specimens, mostly flies and 

 small Hymenoptera, were seen caught by the same kind of 

 grass. 



In 1912 I again came across the grass at Tolga Junction 

 near Cairns in Queensland, but there it was growing i.i the 

 open, at the sides of roads and tracks. In such situations it 

 grows, in rather thick clumps, to a height of about 2 feet, the 

 heads ranging from 5 to 7 inches in length, and being thickly 

 covered with dark (almost black) burr-like objects, these being 

 the seed-coverings. The burrs often catch in horses' manes 

 and tails, in the hair of dogs and wool of sheep, and mat 

 these together, as other burrs do. 



At Tolga Junction many insects were caught by the grass, 

 in particular thousands of a destructive species of ladybird, 

 Epilachna 28 punctata, and of a soldier-beetle, Telephorus 

 mastersi ; a moth measuring 2 inches across the expanded 

 wings was caught, and several fairly large grasshoppers. 

 Many of the specimens were dead and more or less in frag- 

 ments, but many were alive and doing their best to escape. 

 It was not uncommon to see from two to ten insects on one 

 head, and sometimes one insect would be attached to two 

 heads. Fragments of the largest Australian tenebrionid, 

 Chartopteryx imperialis (a bulky beetle measuring over an 

 inch in length), were seen on one head. 



Most of the insects were caught by the hind portion of 

 the body or by the legs, very few by the head. The insects 

 appear to have been crossing in a casual way when the burrs 

 caught and detained them; but no doubt many of them were 

 attracted by the sight of those already trapped, and went 



