210441a0Nature2105034196604234414420028-0836196610.1038/210441a0ukNatureNatureNATUREnatureNature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public./nature/journal/v210/n5034issueJournal homeArchiveCurrent issueAdvance online publicationPrivacy policySubscribeNature Publishing GroupCurrent issue210441a0/`Paper Factor/' as an Inhibitor of the Metamorphosis of the Red Cotton Bug, Dysdercus koenigii F.
AU  - SAXENA, KAILASH N.Department of Zoology, University of Delhi.
AU  - WILLIAMS, CARROLL M.The Biological Laboratories, Harvard University, Cambridge, Massachusetts.MATERIALS composed of American paper-pulp have been shown to contain an extractable, heat-stable lipid which exhibits high juvenile hormone activity when topically applied or otherwise brought into contact with the European bug, Pyrrhocoris apterus L. (Heteroptera; Pyrrhocoridae1,2). The active principle is synthesized by certain species of pulp trees[mdash]more particularly, the American balsam fir (Abies balsamea). The /`paper factor/' (PF) proves to be an extremely potent analogue of the juvenile hormone of Pyrrhocoris apterus3. Yet, so far, it has proved completely inactive when tested on other laboratory insects including two other species of Heteroptera[mdash]Oncopeltus fasciatus (Lygaeidae) and Rhodnius prolixus (Reduviidae)1,2.Pyrrhocoris apterus is a benign species which feeds by its sucking mouthparts on lime (linden) seeds. However, the family Pyrrhocoridae includes some of the world's most troublesome insect pests-notably the 'red cotton bugs' (Dysdercus sp.) indigenous to India, Africa, and Australia. Slama and Williams (p. 414, ref. 1) have considered the possibility that PF "may be effective in the selective destruction of at least certain of these pests, as well as any other insects which show the same hormonal sensitivities as Pyrrhocoris apterus".
The purpose of the present communication is to report that the 'red cotton bug', Dysdercus koenigii-a considerable pest in India and North Africa-is sensitive to PF.
The experiments were performed on an extract of PF prepared at Harvard University from 250 paper towels ('Scott' Brand 150). The towels were packed into a large glass column (11 cm outside diameter x 115 cm long), soaked overnight in absolute methanol, and then perfused with a total of 5 1. of solvent. The methanolic extract was reduced to dryness to obtain 7-4 g of a viscous sludge from which PF was extracted with 4 x 50 ml. portions of petroleum ether (b.p. 35-60 C). The latter was filtered and the solvent evaporated to obtain 2-9 g of viscous greenish-yellow oil. Without further purification, this crude preparation of PF was vised in the present study.
Table 1. EFFECTS OF PAPER FACTOR ON FIFTH-INSTAR Dysdercus LARVAE Percentage of PF-treated individuals showing different-effects
PF extract Imaginal inhibition Incomplete
Sixth ecdysis Adults Adultoids instar larvae Topical application of:
0-01 fig 30 70 0 ()
0-05 20 80 0 (>
0-1 0 100 0 0
0-5 0 50 50 0
1-0 0 30 30 40
4-0 0 0 20 80 Contact with paper[ast] impregnated with:
0-1 mg 0 80 10 10
1-0 0 60 20 20
2-0 0 20 20 60 [ast] A 9 cm disk of Whatnmn No. 1 filter paper.
With the support and encouragement of Prof. B. R. Seshachar, Head of the Zoology Department at the University of Delhi, PF was tested on the same laboratory culture of Dysdercus koenigii which has been subjected to detailed investigations in recent years4. Individual larvae were isolated within 30 min after moulting to the fifth instar. The insects were provided with water -soaked swabs of cotton wool, but were otherwise starved during the first 28-36 h at 27~28 C. A measured droplet of an acetone solution of PF was then applied to the mid-dorsal region of each of 10 individuals in each test group. Alternatively, groups of 10 individuals were placed in glass containers in the presence of a 9-cm disk of Whatman No. 1 filter paper impregnated with a known amount of PF. After these manoeuvres, each group was provided with cottonseed and water to provoke development4.
The results, summarized in Table 1, show that the PF inhibited the metamorphosis of the insect in two ways: (i) by inhibiting the development of imaginal characters in the sixth instar individuals into which the PF-treated fifth instar larvae moulted, and (ii) by preventing complete extrication of the PF-treated fifth instar larvae from the old larval cuticle during the ecdysis. The degree of imaginal inhibition and failure in the extrication of the moulting individuals was a function of the dose of PF, and a topical application of 4 pig at the outset of the fifth instar caused complete suppression of metamorphosis. Most of the treated larvae failed to extricate themselves from the old cuticle during moulting and died in the process. A small number of individuals, however, moulted into a supernumerary sixth larval instar showing complete inhibition of the imaginal characters.
When the topical application was decreased belowT 4 pig (Table 1), the number of individuals showing incomplete ecdysis decreased and a progressively larger number of larvae moulted into apparently normal adults, save for a failure of the wings to attain adult size and form. Many of these 'adultoid' individuals lived for weeks without further moulting, and some were capable of mating and laying fertile eggs.
When the topical application was reduced to 0-05 or 0-01 pig, a few larvae were able to transform into normal adults. But even at such lowT doses, the majority of individuals moulted into 'adultoids' wThich showed partial inhibition of wing development-a finding which indicates that the wings are far more susceptible to inhibition by PF than are other imaginal characters.
As recorded in the lower part of Table 1, the effects of the topical applications were duplicated when three groups of ten larvae were reared throughout the fifth instar in contact with PF-impregnated filter paper; the experiment was repeated five times wTith substantially the same results.
The quantitative aspects of the present investigation indicate that low doses of PF have less extensive and less lethal effects on Dysdercus than on Pyrrhocoris apterus1. The difference in the effects between the two species was, however, far less evident at higher dose-levels. Thus, in the case of Pyrrhocoris, metamorphosis and sexual maturation were completely blocked by the topical application of 1 pig2. This same result was achieved in the present study by 4 pig of a PF extract that was one-third as active as that used in the earlier study.
The ability of PF to block the metamorphosis and selectively to kill an economically important pest such as Dysdercus koenigii is of considerable interest. Though the hormonally active principle is known to be present in only trace amounts in these crude extracts2, the 'starting material' is available on an essentially unlimited scale in the form of American newspapers and other paper products. More highly purified preparations of PF promise to be effective in the selective control oi Dysdercus koenigii and, presumably, of other economically important Pyrrhocoridae. This proposition is at present being tested in Delhi.Slama, , K., and Williams, , C. M., Proc. U.S. Nat. Acad. Sci., 54, 411 (1965).Slama, , K., and Williams, , C. M., Biol. Bull. (in the press).Slama, , K., and Williams, , C. M., Nature (in the press).Saxena, , K. N., Ann. Entomol. Soc. Amer., 55, 218 (1962).