Oncopeltus

Aposematic species from two different families produce pungent pyrazines, presumably as an additional warning to potential predators of their toxicity. These include Oncopeltus fasciatus (Lygaeidae, seed bug family) that secretes 2-isobutyl-3-methoxypyrazine [28], and the stink bug Murgantia histrionica (Pentatomidae), that oozes froth containing 2-isobutyl- and 2-sec-butyl-3-methoxypyrazine when molested [39]. 

Cardenolldes appear to be metabolized by a variety of species, possibly as a mechanism for converting these steroids into compounds that can be efficiently sequestered. The milkweed bug, Oncopeltus fasclatus, metabolizes (hydroxylates ) the nonpolar cardenollde dlgltoxln to more polar compounds that are subsequently sequestered In the dorsolateral space fluid (17. 18). Larvae of another cardenolide-adapted Insect, the monarch butterfly, Danaus plexlppus. also convert these steroids Into compounds that are readily sequestered. For example, uscharldln, which contains a carbonyl group at C-3 ( ) of the... 

Geranylgeranylhydroqulnone (VII) was applied (lOOxg) to fifth Instars of Oncopeltus (mllkbugs) and found to stunt growth and wing development. 

We began to extract plants with apolar solvents and tested these extracts by contact and fumigation against the cotton stainer, Dysdercus cingulatus, and the milkweed bug, Oncopeltus fasciatus. Eventually we found that the extract of the bedding plant, Ageratum houstonianum, contained two potent anti-juvenile hormones. 

The steroids known to play major regulatory roles in insect development and metamorphosis all fall into the class of polyhydroxylated ketosteroids called ecdysones (19-22). With the exception of Makisterone A (a C2 ecdysteroid identified from the milkweed bug Oncopeltus fasciatus) the known insect ecdysteroids constitute a group of eight or nine steroids that differ from one another... 

Preliminary results of antijuvenile hormone bioassays for precocious metamorphosis in immature stages of Oncopeltus fasciatus revealed that some of the non-linear derivatives (VI) showed higher activities and lower toxicities that those exhibited by natural precocenes or 7-ethoxy-6-methoxy-2,2-dimethylchromene, one of the most active synthetic analogs known. In addition, some of these compounds were unexpectedly inactive in the sterilization bioassay with adults of the same species (8). Further investigation of antijuvenile hormone activities of selected compounds of this series in other insects is now in progress. 

Musca domestlca (Linn.), Me = Macroslphum euphorblae (Thomas), Mp = Myzus perslcae (Sulzer), Oa = Oncophanes amerlcanus (Weed), Of = Oncopeltus fasclatus (Dallas), Pf = Pedloblus foveolatus (Crawford),... 

Oncopeltus fasciatus (Dallas) large milkweed bug adult nymph T GR 77 79... 

The Milkweed bug, Oncopeltus tasciatus [168], is unable to dealkylate plant sterols into cholesterol before they are incorporated into the larval or adult tissues or into the egg, and is apparently able to utilize campesterol as a precursor for their Cjg moulting hormone, makisterone A. 

Larvae of the large milkweed bug, Oncopeltus fasciatus treated with precocene II undergo precocious metamorphosis and moult into diminutive forms with adult characters. Freshly hatched females treated with precocene II remain sterile and their corpora allata loose their ability to secrete juvenile hormone even when transplanted into an untreated body (Muller et al., 1979 Masner et al., 1979 Pener et al., 1978). 

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