Tobacco larvae

The larvae that hatch from Cotesia eggs remain inside their caterpillar host, exploiting it as a secure haven from the outer world and a convenient food supply. They feed on the caterpillar from within until they are mature and ready to pupate. Then they emerge from its body and immediately begin spinning small white cocoons, which they attach by one end to the caterpillar s back. It is not uncommon for a tobacco hornworm, still alive, to be festooned with fifty or more Cotesia cocoons, each resembling a diminutive grain of rice fastened to the caterpillar. Each cocoon contains... 

The combination of the wasps own toxins and those provided by the virus affect tobacco hornworms in other ways as well. One of these is to modify their behavior to the wasps benefit. Parasitized caterpillars continue to feed and behave normally until about eight hours before the larvae emerge. At that time, the caterpillars cease to eat and crawl about. They show no other deficiency and their reflexes appear normal. The details of this modification are uncertain, but it appears to favor the wasp larvae. A normal, unparasitized caterpillar readily eats wasp pupae offered to it. This implies that an active caterpillar would be a threat to larvae emerg-... 

Several species of lepidopterous larvae cause bollworm-type injury to bolls and squares throughout the tropics. They include the bollworm [Heliothis armigera (Hbn.)], the tobacco budworm [Heliothis virescens (F.)], the black bollworm (Pro-denia latisfascia Wlk.), and in Peru Mescinia peruella Schaus. 

Polles, S.G. and Vinson, S.B. Effect of droplet size on persistence of malathion and comparison of toxicity of ULF and EC malathion to tobacco budworm larvae, / Econ. EntomoL, 62 89-94, 1969. 

These same two diterpenes were subjected to the tobacco hornworm assay. Brlantheln Y, 10, was quite toxic at 250 ppm, killing the exposed larvae within thirty hours. There appeared to be no inhibition of feeding. On the other hand, the less functionalized brlanthein W, 12, elicited only 50 percent mortality over five days, and the surviving larvae suffered from extremely poor weight gains (only 6J of controls) despite feeding freely on the treated diet. 

In experiment A, newly ecdysed fifth stadium tobacco hornworm larvae received 5 jiCi of labeled compound and 1 mg canavanine/g fresh body weight. Three hrs later, the treated larvae were collected and processed. In experiment B, canavanine was injected first and 24 hrs later, the labeled compound was administered. All larvae were collected and processed 3 hrs later (from the work of Rosenthal and Dahlman). 

Examination of this question with the tobacco hornworm, an insect known to be canavanine-sensitive (this insect normally feeds on canavanine-free plants) revealed that it readily incorporates [ C]canavanine into its newly synthesized proteins. Caryedes brasiliensis. however, very effectively avoids the production of such radiolabeled proteins. When the arginyl- RNA synthetase activity of these insects was compared, tobacco hornworm larvae readily activated canavanine while the larvae of the bruchid beetle possess an arginyl- tRNA synthetase with a marked ability to discriminate between arginine and its structural analogue (22). 

Little is known of canaline toxicity in whole animals or plants. Canaline-fed tobacco hornworm larvae grew poorly, exhibited much more deformity, and succumbed in larger numbers than the controls (8). This ornithine analogue is neurotoxic to the adult moth where it induces almost continuous motor activity. 

Shaver and Parrott (17) reared bollworm and tobacco budworm larvae on a standard larval diet, and transferred them at 5 ages onto media containing 0-0.4% gossypol. The Influence on development Increased with larval age at the time of transfer. Recently Wales and his co-workers (18) Incorporated condensed tannin In diets fed to the tobacco budworm where the larvae Initially were of different ages. The ED5Q values were as follows 1 day,... 

First instar tobacco budworm larvae were restrained in 15 cm long dialysis casings that were slipped over the terminals, and collected and weighed after five days. Adequate numbers and replications were employed for statistical evaluation. 

Conclusive held evidence has been obtained with the manipulation of odor emissions of free-standing plants. Thaler (1999), for example, observed an increase in parasitism of S. exigua larvae on tomato after the plants had been treated with JA. This treatment induces the octadecanoid pathway, which results in the production of various defense compounds, including volatiles. In an earlier study in a tobacco held, De Moraes et al. (1998) had already found that the specialist parasitoid... 

The macrolide halichondramide (3)62 showed more than 75% mortality (100 ppm) against newly hatched larvae of the southern com rootworm, Diabrotica undecimpunctata howardi, and the tobacco budworm, Heliothis virescens.44 The dimeric macrolides swinholide A and... 

One of the insect neurohormones, the activation hormone, controls the secretion of the corpora allata, paired glands that synthesize the juvenile hormone (Fig. 22-4) in insect larvae. While the structure of the juvenile hormone varies somewhat with species, it is usually a polyprenyl ester. A specific binding protein provides the hormone with protection from degrada-tive enzymes. However, in the tobacco homworm an esterase, able to hydrolyze the protein-bound juvenile hormone, is produced at the start of pupal differentiation.354 The exact mechanism of action of juvenile hormones has been difficult to determine. However, it affects polyamine synthesis.355 356... 

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