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Research on larval rearing and nutrition of tephritid flies on artificial diets is key for the sterile insect technique. Here, we examined the effects of the type of gel (calcium alginate, agar, or carrageenan), at varying percentages in artificial diets for the polyphagous pest Anastrepha ludens , on the physicochemical and nutritional traits of the diets, and the effects of the type of gel, the gel content and the larval density (larvae/g of diet) used in production, quality parameters for mass-reared tephritids, diet removal (an indirect estimation of diet consumption), and nutritional traits of flies. Regardless of the gel content, calcium alginate diets were firmer and more resistant to penetration than the agar and carrageenan diets. The larval recovery, pupation, pupal weight, and flight ability of A. ludens were lower in calcium alginate diets than in agar and carrageenan diets. Diet removal was higher in calcium alginate diets; however, low levels of ammonium and high levels of uric acid in excretions from larvae on these diets suggest an alteration in protein metabolism. The firmness and penetration resistance characteristics of calcium alginate diets may have limited movement and feeding of larvae, but this could be overcome by the collective feeding of large groups of larvae. Our findings provide insights into the mechanism governing gel-diet rearing systems for A. ludens .

Using light, transmission, scanning electron, and confocal microscopy, we carried out a morphological study of antennal sensilla and their ultrastructures of the Mexican Fruit Fly Anastrepha ludens (Loew), an economically important species that is a pest of mangos and citrus in Mexico and Central America. Our goal was to update the known information on the various sensilla in the antennae of A. ludens , involved in the perception of odors, temperature, humidity, and movement. Based on their external shape, size, cuticle-thickness, and presence of pores, we identified six types of sensilla with 16 subtypes (one chaetica in the pedicel, four clavate, two trichoid, four basiconic, one styloconic, and one campaniform-like in the flagellum, and three additional ones in the two chambers of the sensory pit (pit-basiconic I and II, and pit-styloconic)), some of them described for the first time in A. ludens . We also report, for the first time, two types of pores in the sensilla (hourglass and wedge shapes) that helped classify the sensilla. Additionally, we report a campaniform-like sensillum only observed by transmission electronic microscopy on the flagellum, styloconic and basiconic variants inside the sensory pit, and an "hourglass-shaped" pore in six sensilla types. We discuss and suggest the possible function of each sensillum according to their characteristics and unify previously used criteria in the only previous study on the topic.

Chemical ecology studies on ambrosia beetles are typically conducted with either wild or laboratory-reared specimens. Unlike laboratory-reared insects, important aspects that potentially influence behavioral responses, such as age, physiological state, and prior experience are unknown in wild specimens. In this study, we compared the electroantennographic (EAG) responses of laboratory-reared and wild X. affinis and X. ferrugineus to 70% ethanol and bark odors (host kairomones) of Bursera simaruba , Mangifera indica , and Persea schiedeana aged for 2, 24, and 48 h. Chemical analyses of each odor treatment (bark species x length of aging) were performed to determine their volatilome composition. EAG responses were different between laboratory-reared and wild X. ferrugineus when exposed to ethanol, whereas wild X. affinis exhibited similar EAG responses to the laboratory-reared insects. Ethanol elicited the strongest olfactory responses in both species. Among the bark-odors, the highest responses were triggered by B. simaruba at 48 h in X. affinis , and P. schiedeana at 24 and 48 h in X. ferrugineus . Volatile profiles varied among aged bark samples; 3-carene and limonene were predominant in B. simaruba , whereas α-copaene and α-cubebene were abundant in P. schiedeana. Further studies are needed to determine the biological function of B. simaruba and P. schiedeana terpenes on X. affinis and X. ferrugineus, and their potential application for the development of effective lures.

With the aim of identifying key factors that determine oviposition decisions by Anastrepha obliqua for management purposes, we conducted a behavioral study under natural/semi-natural field conditions to identify where exactly in the fruit (upper, middle, or lower sections) females preferred to lay eggs in a highly susceptible mango cultivar ("Criollo"), and whether sunlight incidence and fruit chemical compounds influenced oviposition site selection by this pestiferous fly. Females oviposited in shaded, upper fruit sections where pulp had higher total carbohydrate concentrations but similar total protein, lipid, and polyphenol concentrations than non-oviposited sections. Peel had higher overall nutrient and mangiferin/quercetin-3-D-galactoside (polyphenols) concentrations. An untargeted metabolomic analysis of oviposited and non-oviposited fruit sections identified abscisic acid (ABA) and dihydrophaseic acid glucoside, a by-product of ABA catabolism, as potential chemical markers that could play a role in fruit acceptance behaviors by female flies. We conclude that females preferentially oviposit in fruit sections with optimal chemical and environmental conditions for larval development: more carbohydrates and antioxidants such as mangiferin and ferulic acid and lesser sunlight exposure to avoid lethal egg/larval desiccation/overheating. We make specific recommendations for A . obliqua management based on female host selection behavior, a tree pruning scheme exposing fruit to direct sunlight, application of a host marking pheromone, and the use of egg sinks in the orchard.

Adequate pupation substrates and substrate volume are critical factors in the mass-rearing of insects for Sterile Insect Technique (SIT) applications. To identify an ideal pupation substrate for a reproductive colony of Ceratitis capitata (Wiedemann) VIENNA 8 genetic sexing strain, we first examined pupation in cellulose from recycled paper (cellulose I), sawdust, fine wheat bran, vermiculite and coconut fiber using a volume of 2.5-12.5 mL of substrate for each 5 mL volume of fly larvae. We found a positive relationship between substrate volume and pupation, with cellulose I generating the highest proportions of pupation and coconut fiber the lowest. Higher proportions of female flies (white pupae) pupated in sawdust. The proportion of female fliers increased as substrate volume rose in sawdust and coconut fiber, whereas it decreased in vermiculite and cellulose. In a second experiment, we tested three types of cellulose differing in physicochemical characteristics (celluloses I, II and III), sawdust, and fine wheat bran using a substrate:larvae ratio of 1:1. The three types of cellulose produced the highest pupation levels. The highest proportions of female fliers were observed in sawdust, and cellulose types III and II. Cellulose III and sawdust at relatively low volumes were more cost-effective to produce one million pupae than other substrates, including fine wheat bran used in a mass-rearing facility in Mexico.

In insects, the quality of sex pheromones plays a critical role in mating success and can be determined by the ability of larvae/adults to accrue chemical precursors. We tested the host-quality-effect hypothesis by analyzing the chemical composition of scent bouquets emitted by calling males of two polyphagous tephritid species ( Anastrepha ludens and A . obliqua ) that originated from 13 fruit species representing diverse plant families. In A . ludens , we worked with an ancestral host (Rutaceae), nine exotic ones (Rutaceae, Anacardiaceae, Rosaceae, Solanaceae, Lythraceae), and two species never attacked in nature but that represent candidates for host-range expansion (Solanaceae, Myrtaceae). In A . obliqua , we tested an ancestral, a native, and an exotic host (Anacardiaceae), one occasional (Myrtaceae), and one fruit never attacked in nature (Solanaceae). We identified a core scent bouquet and significant variation in the bouquet's composition depending on the fruit the larvae developed in. We also tested the possible microbial role on the scent bouquet by treating adults with antibiotics, finding a significant effect on quantity but not composition. We dwell on plasticity to partially explain our results and discuss the influence hosts could have on male competitiveness driven by variations in scent bouquet composition and how this could impact insect sterile technique programs., Competing Interests: The authors declare no conflict of interest.

The development of cost-effective diets for mass-rearing fruit flies (Diptera: Tephritidae) and their parasitoids in pest control programs based on the Sterile Insect Technique is a high priority worldwide. To this end, we tested carrageenan, agar, gelatin and two types of pregelatinized corn starches as gelling agents at varying percentages in a yeast-reduced liquid larval diet for rearing the Mexfly, Anastrepha ludens . Only diets with 0.234% ( w / w ) agar or 0.424% carrageenan were identified as diets with potential for mass-rearing A. ludens in terms of the number of pupae recovered from the diet, pupal weight, adult emergence, flight ability and diet cost. Comparative experiments showed that yeast-reduced agar and carrageenan gel diets produced heavier pupae and higher proportions of flying adults than the standard mass-rearing diet. The gel-agar and mass-rearing diets produced more pupae than the gel-carrageenan diet, but the latter produced more suitable larvae as hosts for rearing of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) females, a widely used fruit fly biocontrol agent. Yeast-reduced agar and carrageenan gel diets could represent cost-effective fruit fly mass-rearing diets if a practical system for gel diet preparation and dispensation at fruit fly mass-rearing facilities is developed.

Scientifically-based, tephritid fly host status determination lies at the heart of strategic regulatory decisions impinging on international fruit trade. Here we conducted intensive field and laboratory studies with peaches as controls, to determine the host status of Physalis peruviana for the Medfly- Ceratitis capitata , as this fruit is experiencing a consumption boom worldwide. A total of 98,132 Uchuvas (local name), collected in Colombia from the plant or the ground over a three-year period (2016-2018) did not yield a single C . capitata larva or pupa, thus reaching a Probit 9 level with 99.9968% efficacy and 96% confidence level. Field-cage studies with enclosed fruit-bearing Uchuva plants, exposing fruit with an intact, damaged or totally removed husk to the attack of C . capitata are repellent/toxic to insects, we conclude that this plant should be treated as a non-natural and non-conditional host of P . peruviana are repellent/toxic to insects, we conclude that this plant should be treated as a non-natural and non-conditional host of C . capitata .