Introduction of coccinellid beetles to control the coconut scale insect Aspidiotus destructor Signoret in Micronesia 1901–1914

ABSTRACT

The present-day composition and distribution of diaspidid scale and coccinellid beetle species in the Pacific is an amalgam of endemic distribution, and naturalisations or extirpations following unintentional accidental dispersal as well as intentional dispersal as part of biological plant pest control measures. Using primary sources, historic biogeography not only allows us to untangle the nature and sequence of introductions but also to assess which species have endured. This paper is a case study of early twentieth century coccinellid beetles introductions to Micronesia. When faced with the spectre of a collapse of the local copra industry on Yap, the German colonial administration in Micronesia embarked on an ambitious program to eradicate, or at least contain the coconut scale insect. To this end numerous species of coccinellid beetles were introduced from within the Western Pacific (Saipan, New Britain) as well as from the outside (Australia, China, Philippines).

KEYWORDS:

• Biogeography
• biological pest control
• naturalisation

Disclosure statement

No potential conflict of interest was reported by the author.

Notes

1. For the changes to the administrative structures and hierarchies in German Micronesia, see Spennemann (2007).

2. We are uninformed as to the species of coccinellid beetles that were introduced, how many were sent, who had sent them or from which location in the Philippines that had been sourced. – Banks (1906) in his review of ‘principal insects attacking the coconut palm’ in the Philippines, notes that a Scymnus sp with light brown discal spots on each elytron, was noted as a voracious feeder of CSI. While this species has not been positively identified itself, is possible that it was this species coccinellid beetle that was introduced to Yap.

3. Dumbleton (1957) claims a 1907 introduction of Harmonia (Leis) conformis Boisduval, 1835 and a 1908 introduction of Halmus (Orcus) chalybeus Boisduval, 1835, both from Australia to Yap.

4. In that instance, the beetles were shipped in wooden boxes which contained potted plants and herbs favoured by the beetles. One has to presume that the plants were infested with aphids on which the coccinellid beetles fed. As the actual plants were planted out on Palakuwur, other species not native to Palakuwur may have been introduced (Rudolph 1909).