The Scolia Wasp
p. 45 · Read in the full issue
How It Helps to Control the Rhinoceros Beetle
IN reply to a letter concerning the Scolia wasp, written by Mr. Massingham Folkard and published in the Janu ary “PIM,” an officer of the Department of Agriculture, Fiji, has sent us a pamph let dealing with the biological control of the rhinoceros-beetle. This pamphlet (Bulletin No. 21). written by Hubert W.
Simmonds, formerly Government Ento mologist, can be obtained from the Department’s Suva office.
Briefly, it gives the history of early investigations into rhinoceros-beetle con trol as follows: In April, 1912, Mr. F. P. Jepson, then Government Entomologist in Fiji, visited Western Samoa and reported upon the ravages of the beetle in that territory.
Following his report, stringent regula tions were imposed upon all ships coming to Fiji from Western Samoa.
In 1913, a Dr. K. Fredericks made an extensive tour of the eastern tropics in search of natural enemies of the pest.
His investigations, however, were stopned by the outbreak of World War I, just when he had reached Madagascar. In his report, he suggested the introduction into Samoa of the Madagascar Scolids.
In 1933, Mr. Simmonds was seconded for three months to Samoa to report on the position and later he undertook a special mission to Malaya, Mauritius and Madagascar to ascertain what factors, if any, held the pest in check in those countries.
The discovery of the black wasps in Zanzibar and their recent introduction into Western Samoa was described in the October issue of “PIM.”
In his letter, Mr. Folkard asked also for a description of how the Scolia wasns combatted the rhinoceros-beetle. Mr.
Simmons in his pamphlet states that no true parasite of the beetle has been proved to exist. In the laboratory, how ever, Scolia wasps are notorious 'for at tacking the grubs of the rhinoceros-beetle and there is no reason to suppose they do not continue to do so in the field.
All Scoliidae are parasitic in the larval stage, living as external parasites upon the grubs of certain beetles.
To oviposit, the adult female wasp bur rows into the soil, rotten wood or other media where the beetle grub occurs, and then having discovered a suitable one for her purpose, she paralyses it by means of her sting and, prior to laying an egg upon it, generally removes it more deenlv into the media, where she seals it up in a cell of her own construction.