Parasites and parasitism
Of course the leaves of Ceropegia are consumed by different kinds of insects, yet there appear not to be much information of such cases, but an example is given in O. A. Leistner’s “Flora of Southern Africa”, 1980.:
“It is difficult to get complete specimens with seed, flowers and leaves, as the last are usually stung by some fly and drop off when the maggots hatch.”
(source: H. R. Brownlee in 1935 while studying Ceropegia plant material) 
The fruit fly species Dacus apoxanthus Bezzi (family Tephritidae) is known to parasitize the flower buds of Ceropegia ampliata E. Mey., resulting in the flower buds becoming translucent, and in the flowers wilting thereafter. 
I hope that there will be more studies to come.
 O. A. Leistner: Flora of Southern Africa 27(4). Botanical Research Institute, Dept. of Agricultural Technical Services 1980
 Gareth Coombs; Anthony P. Dold; Craig I. Peter: Generealized fly-pollination in Ceropegia ampliata (Apocynaceae – Asclepiadoideae): teh role of trapping hairs in pollen export and receipt. Plant Systematics and Evolution 296(1): 137-148. 2011