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The host acceptances of insects can be determined largely by detecting plant metabolites using insect taste. In the present study, we investigated the gustatory sensitivity and feeding behaviors of two closely related caterpillars, the generalist Helicoverpa armigera (Hübner) and the specialist H. assulta (Guenée), to different plant metabolites by using the single sensillum recording technique and the dual-choice assay, aiming to explore the contribution of plant metabolites to the difference of diet breadth between the two species. The results depicted that the feeding patterns of caterpillars for both plant primary and secondary metabolites were significantly different between the two Helicoverpa species. Fructose, glucose, and proline stimulated feedings of the specialist H. assulta, while glucose and proline had no significant effect on the generalist H. armigera. Gossypol and tomatine, the secondary metabolites of host plants of the generalist H. armigera, elicited appetitive feedings of this insect species but drove aversive feedings of H. assulta. Nicotine and capsaicin elicited appetitive feedings of H. assulta, but drove aversive feedings of H. armigera. For the response of gustatory receptor neurons (GRNs) in the maxillary styloconic sensilla of caterpillars, each of the investigated primary metabolites induced similar responding patterns between the two Helicoverpa species. However, four secondary metabolites elicited different responding patterns of GRNs in the two species, which is consistent with the difference of feeding preferences to these compounds. In summary, our results of caterpillars’ performance to the plant metabolites could reflect the difference of diet breadth between the two Helicoverpa species. To our knowledge, this is the first report showing that plant secondary metabolites could drive appetitive feedings in a generalist insect species, which gives new insights of underscoring the adaptation mechanism of herbivores to host plants.

Medium-sized ring-containing organic molecules, especially the seven-membered rings, are significant structural motifs. However, such frameworks are considered as difficult structures to access owing to entropic effects and transannular interactions. Compared...

Key indicators: single-crystal X-ray study; T = 173 K; mean (C-C) = 0.004 Å; disorder in solvent or counterion; R factor = 0.037; wR factor = 0.099; data-toparameter ratio = 14.8.In the title polymer, {[Ag(C 14 H 10 N 4 O) 2 ]PF 6 } n , each Ag I ion is coordinated by two N atoms from two pyridyl rings of independent N 0 -(4-cyanobenzylidene)nicotinohydrazide ligands, and one N atom from one carbonitrile group of a symmetry-related ligand in a distorted T-shaped geometry. The ligands exhibit two modes of coordination. One acts as a bridge connecting Ag atoms to form one-dimensional chains along [101]. The other acts as a terminal monodentate ligand, coordinating to Ag through its pyridyl N atom. Two neighbouring antiparallel chains in the crystal are connected through N-HÁ Á ÁO hydrogen bonds. Other adjacent chains are packed via AgÁ Á ÁO interactions, with AgÁ Á ÁO separations of 2.876 (2) Å . In addition, PF 6 À counter-anions interact with the hydrazone groups through N-HÁ Á ÁF hydrogen bonds. The PF 6 À anion is disordered over two sites, with occupancies of 0.773 (8) and 0.227 (8). Related literature

C 36 H 32 Cl 2 CoN 12 O 12 S 3 , triclinic, P1 (no. 2), a = 9.820(2) Å, b = 10.806(2) Å, c = 11.120(2) Å, a = 74.198(2)°, b = 82.053(2)°, g = 69.880(2)°, V = 1064.8 Å 3 , Z = 1, R gt(F) = 0.106, wRref(F 2 ) = 0.289, T = 291 K. Source of materialThe ligand 2,5-bis(2-pyridyl)-1,3,4-thiadiazole was prepared according to the literature procedure [1]. The ligand (0.024 g, 0.1 mmol) and 2,5-dimethyl-pyrazine (0.011 g, 0.1 mmol) dissolved in a mixture of 5 ml chloroform and 5 ml methanol were added to 10 ml methanol solution of cobalt acetate tetrahydrate (0.025 g, 0.1 mmol) while stirring. The ammonium perchlorate (0.024 g, 0.2 mmol) solution in 5 ml water was added dropwise after 20 min. Suitable red block-like crystals were obtained by slow evaporation of the solvents in about 40 days (yield 62 %). Experimental detailsThe large R values may be caused by the disordered thiadiazole ring and disordered perchlorate anion. Z. Kristallogr.