308 



THREE LEPIDOPTERA WHICH ATTACK 

 DIOSCOREAS IN SINGAPORE. 



In the course of two years ob nervations on Dioscoreas in Singa- 

 pore, the caterpillars of throe lepidoptera have attracted attention. 

 They are : — 



Theretra nessiis, Moore 



Loxura atymmis, Horsf. and 



Tagiades gana, Butl. 



The second is the most injurious. 



Theretra tiessus is a Sphingid, already recorded as attacking the 

 common yam {Dioscorea alata, Linn.). Owing to the large size 

 which the caterpillar attains, the number of leaves consumed is 

 considerable; but as the eggs are laid singly, the injury to a plant 

 is generally restricted to what is required to satisfy the appetite of 

 one individual. 



Offered a choice of food-plants of the genus Dioscorea, the 

 caterpillars refused none; but they ate the leaves of D. alata, Linn., 

 D. pyrifolia, Kunth, D. bulbifera, Linn., D. pentaphylla. Linn., and of 

 a Philippine ally of the last which is thought to be D. Cumbigii, Prain 

 and Burkill, in preference to those of D. aculeata, Lamk., and 

 D. triphylla, Linn. It is known that dioscorine is present in the 

 leaves of the last named; but the surface is covered with small 

 bristly hairs; and it is likely that the hairs deterred to caterpillars 

 from feeding readily more than any dioscorine present. 



The moth of Theretra fiessus is figured in Moore's Lepidoptera 

 of Ceylon, (1882-83), plate 86, and there is a description of it on p. 22 

 of volume ii. 



Across the fore wings the moth is II cm. The general colour is 

 dull red and olive green above, but below orange. The fore wings are 

 nearly white at the tip, and white on the fore margin ; behind this are 

 diagonal belts of olive green, smoky grey and dull salmon. The 

 caterpillar is of a pale green, streaked with white down the back 

 and obliquely on the sides, the streaking" ill-defined; and it has two 

 defined white spots forward, which when it has been disturbed and has 

 drawn in its head, have somewhat the position in which eyes might 

 be expected. It attains a length of 14 centimetres (5J/3 inches). At 

 maturity it spins a cocoon of a rather small amount of silk among 

 leaves, drawing them together; and when it turns into a chrysalis is 

 upwards of 1 1 cm., long, streaked in various shades between buff and 

 claret. 



The caterpillar of Loxura atymmis is a green slug-like object which 

 eats the very young parts of the plant. So far it has only been 

 found on Dioscorea alata, on D. anguina Roxb., and on an imported 

 African yam. The eggs are laid singly, but many to a plant, on the 

 tips of growing shoots, and the caterpillar devours by preference the 



