Oviposition-stimulatory activity of phenanthroindolizidine alkaloids of host-plant origin to a danaid butterfly, Ideopsis similis

Oviposition response of Ideopsis similis (L.) (Lepidoptera: Danaidae) was examined for 12 phenanthroindolizidine alkaloids present in its host plant, Tylophora tanakae (Maxim.) (Asclepiadaceae). At least five alkaloids, i.e. (+)‐isotylocrebrine (3,4,6,7‐tetramethoxyphenanthroindolizidine; l ), (+)‐3‐demethyliso‐ tylocrebrine ( 3 ), (+)‐isotylocrebrine N‐oxide ( 5 ), (+)‐6‐demethyltylocrebrine ( 8 ) and (–)‐7‐demethyltylophorine ( 10 ), were found to individually stimulate oviposition by females. Of these, compounds 1, 3 and 10 were regarded as key components most responsible for host recognition or preference. However, female egg‐laying was much higher in response to a mixture of the five alkaloids. In two‐choice bioassays, more eggs were deposited on samples comprising the five alkaloids than on samples consisting of a single alkaloid. This suggests strongly that host selection by the butterfly is mediated by the synergistic action of several phenanthroindolizidine alkaloids present in the host plant.     

Response of Danaus plexippus to pollen of two new Bt corn events via laboratory bioassay

Laboratory bioassays were conducted to evaluate the response of first instar larvae of the monarch butterfly, Danaus plexippus L. (Lepidoptera: Danaidae), a non‐target species, to pollen from corn, Zea mays L. (Commelinales: Poaceae), from two new corn hybrids genetically modified to express different types of insecticidal proteins derived from the bacterium Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) (Bt). One hybrid expresses both Cry1Ab and Cry2Ab2 proteins (MON 810 × MON 84006), active against lepidopteran pests, and the other expresses Cry3Bb1 protein (MON 863), targeted against coleopteran pests. First instar larvae were placed on milkweed leaves (Asclepias syriaca L.) (Gentianales: Asclepiadaceae) dusted with doses of either Bt pollen or its nonexpressing (isoline) pollen counterpart ranging from 50 to 3200 grains cm^?2 of milkweed leaves, or no pollen at all. Larvae were exposed to pollen for 4 days, then moved to pollen‐free leaves and observed for another 6 days. Survival was observed after 2, 4, and 10 days. Weight gain was estimated after 4 and 10 days, leaf consumption after 2 and 4 days, and larval development after 10 days. Exposure to pollen of the Cry1Ab/Cry2Ab2‐Bt expressing hybrid reduced larval survival approximately 7.5–23.5% at the dose ranges tested relative to a no pollen control. Larval weight gain and consumption were reduced for larvae exposed to pollen of this hybrid and a small minority of larvae (3.1%) never developed past the third instar after 10 days of observation. Exposure to pollen of the Cry3Bb1‐Bt expressing hybrid had no negative effects on larval mortality, weight gain, consumption, or development relative to the consumption of Bt‐free corn pollen. The relevance of these findings to the risk that these Bt corn hybrids pose to monarch populations is discussed.     

Cardenolide content of Danaus chrysippus butterflies from three areas of East Africa

The African butterfly Danaus chrysippus , like other members of the family Danaidae, feeds as a larva on species of milkweeds (Asclepiadaceae). It has been demonstrated in a sample from a West African population that only a minority of adult D. chrysippus accumulated detectable amounts of poisonous and presumably emetic cardenolides from their larval foodplants. It has also been shown in D. chrysippus and the related monarch butterfly ( D. plexippus ) that the cardenolide content of adults varies with that of their respective milkweed foodplants.
Three population samples of D. chrysippus from sites in East Africa are analysed for cardenolides using the spectrophotometric technique refined by Brower, Edmunds & Moffitt (1975), which allows the assay of individual butterflies. The East African samples all have a palatability spectrum with a considerably higher percentage of cardenolide-containing individuals than the West African one.
This is discussed in terms of its effect on potential bird predators and the 'automimicry' of emetic by palatable individuals. In East Africa D. chrysippus is polymorphic and appears to act as a model in a complex mimicry ring, whereas in West Africa it is monomorphic and may have 'shed' most of its mimics. This latter hypothesis is discussed in the light of our results.     

中国蝴蝶新种新亚种及新记录种(IV)(鳞翅目)

记述斑蝶科 1新种、1新记录种 ;蚬蝶科 2新种、3新亚种。所有模式标本均保存在西北农林科技大学昆虫博物馆。     

Major components in the hairpencil secretions of Danaid butterflies from Far East Asia

A survey of the components in the hairpencil secretions of 10 species of danaid butterflies from Japan and Formosa has been carried out to indicate whether they provide information of taxonomic significance compared to American, African and Australian species. The Far East species contained hydroxydanaidal and/or danaidone and the genus Euplosa contained trans-β-ocumene and linalool in addition. These results suggest that the components of the secretion of Far East species are very similar to those in danaids from Australia.     

A danaid butterfly, Ideopsis similis, overcomes parasitization by a tachinid fly, Sturmia bella

The danaid butterfly Ideopsis similis, which occurs in the Ryukyu Islands, Japan, is a sedentary and monophagous species, whose larval food plant, Tylophora tanakae (Asclepiadaceae), is shared with the migratory and polyphagous danaid Parantica sita. The tachinid Sturmia bella is known to be a principal parasitoid of larval P. sita, whereas there have been no records of parasitization of I. similis by this tachinid. We conducted laboratory experiments and field surveys at seven sites in the Ryukyu Islands to determine how I. similis evades parasitization by this tachinid. We found eggs of S. bella at four sites and eggs and/or larvae of I. similis on the leaves of T. tanakae at all seven sites in the field survey. Out of 40 I. similis allowed to ingest S. bella eggs, 28 (70%) emerged as normal host adults and nine (22.5%) emerged as host adults with crippled wings. Only three (7.5%) died of parasitization in the pupal stage, whereas 27 (87%) of 31 P. sita given S. bella eggs yielded parasitoid flies and eventually died. Melanized dead larvae of S. bella were found in the abdomens of the I. similes adults that had been parasitized but did not yield parasitoid flies. When I. similis females parasitized by S. bella were released in a greenhouse with males, one of them laid fertile eggs. Out of 125 field‐collected I. similis adults, nine had melanized dipteran larvae within their abdomens, which were considered to be S. bella. These results demonstrate that I. similis has the ability to overcome parasitization by S. bella and develop into a fertile adult. It is possible that I. similis remains sedentary and monophagous because it has a strong defense mechanism against S. bella, whereas P. sita escapes from parasitization using its migratory and polyphagous capability.