Particle film deters oviposition by Diaprepes abbreviatus (Coleoptera: Curculionidae)

A hydrophilic formulation of the inert silicate kaolin was tested in a screenhouse for its effect on the behavior of the root weevil Diaprepes abbreviatus (L.), a pest of citrus and ornamental plants in Florida and the Caribbean. Feeding by adults on treated foliage was reduced by 68-84% compared with adults fed untreated foliage. No insecticidal activity was detected after 14 d of exposure to kaolin-treated leaves. Oviposition was completely suppressed on treated foliage. Although females oviposited >19,000 eggs during two trials on untreated foliage, no egg masses were found on foliage treated with the kaolin formulation. These data indicate potential for kaolin as a barrier to oviposition in citrus groves and may prove to be an economically viable and environmentally sound component of an integrated approach for control of D. abbreviatus and related root weevils.     

Reduced oviposition by Diaprepes abbreviatus (Coleoptera: Curculionidae) and growth enhancement of citrus by Surround particle film

Regularly applied sprays of a particle film, Surround WP, greatly enhanced the growth of citrus trees on a poorly drained Winder soil at Fort Pierce, FL. After 3 yr of applications every 3 or 4 wk, Surround-treated trees had at least 5 times the mass, 6 times the canopy volume, and approximately 4 times the cross-sectional area of the tree stems at the graft union compared with untreated trees. The larger Surround-treated trees attracted a higher number of adult weevil Diaprepes abbreviatus (L.) and to a lesser extent citrus root weevil, Pachnaeus litus (Germar), per tree, but there was an equivalent number of egg masses per tree compared with the control trees. The number of egg masses per female weevil oviposited on Surround-treated trees was significantly less than either the control trees or trees treated biannually with an entomopathogenic nematode, BioVector. The number of larvae per tree recovered from the roots of excavated trees was greater from trees treated with Surround once every 3 wk compared with control trees. The data suggest that Surround particle film greatly enhanced the growth of citrus trees grown in a poorly drained soil. The reduction in oviposition by D. abbreviatus was insufficient to significantly reduce the number of root weevil larvae per tree feeding on the roots. However, the more vigorous trees resulting from Surround applications may be more resistant or tolerant to root weevil feeding.     

Virulence of entomopathogenic nematodes to Diaprepes abbreviatus (Coleoptera: Curculionidae) in the laboratory

The Diaprepes root weevil, Diaprepes abbreviatus (L.) is the most severe weevil pest in Florida citrus. Entomopathogenic nematodes have effectively suppressed larval populations of D. abbreviatus. Our objective was to conduct a broad laboratory comparison of entomopathogenic nematodes for virulence toward larvae of D. abbreviatus. The study was conducted at three temperatures (20, 24, and 29 degrees C) and included nine entomopathogenic species and 17 strains: Heterorhabditis bacteriophora Poinar (Baine, NJl, Hb, Hbl, HP88, and Lewiston strains), H. indica Poinar, Karunakar & David (original and Homl strains), H. marelatus Liu & Berry (IN and Point Reyes strains), H. megidis Poinar, Jackson & Klein (UK21l strain), H. zealandica Poinar (NZH3 strain), Steinernema riobrave Cabanillas, Poinar & Raulston (355 strain), S. carpocapsae (Weiser) (All strain), S. feltiae (Filipjev) (SN and UK76 strains), and S. glaseri (Steiner) (NJ43 strain). At 20 degrees C, the greatest mortality was caused by S. riobrave although it was not significantly greater than H. bacteriophora (Baine), H. bacteriophora (Hb), H. bacteriophora (Hbl), and H. indica (original). At 24 and 29 degrees C, S. riobrave caused greater larval mortality than other nematodes tested. Two strains of H. indica, H. bacteriophora (Baine), and S. glaseri were next in terms of virulence at 29 degrees C. Our results suggest that S. riobrave has the greatest potential for control of D. abbreviatus.     

Gut chitin synthase and sterols from larvae of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Gut chitin synthase was characterized and the sterols and ecdysteroids in the sugarcane rootstalk borer weevil, Diaprepes abbreviatus, were identified. An in vitro cell-free chitin synthase assay was developed using larval gut tissues from D. abbreviatus. Subcellular fractionation experiments showed that the majority of chitin synthase activity was located in 10,000g pellets. The gut chitin synthase requires Mg²⁺ to be fully active: 7–8-fold increases in activity were obtained with 10 mM Mg²⁺ present in reaction mixture. Calcium also stimulated activity (4–5-fold with 10 mM Ca²⁺), while Cu⁺² completely inhibited at 1 mM. Other monovalent and divalent cations had little or no effect on activity. The pH and temperature optima were 7 and 25°C, respectively. Gut chitin synthesis was activated ca. 50% by trypsin treatments. GlcNAc stimulated chitin synthase activity, but Glc, GlcN and glycerin did not. Polyoxin D, UDP, and ADP inhibited the chitin synthase reaction with I₅₀'s of 75 μM, 2.3 mM, and 3.6 mM, respectively. Nikkomycin Z was a potent inhibitor of chitin synthase (91% inhibition at 10 μM). Tunicamycin and diflubenzuron had no effect on the enzyme. The apparent Km and V_max for the gut chitin synthase were, respectively, 122.5 ± 7.4 μM and 426 ± 19.7 pmol/h/mg protein utilizing UDP-GlcNAc as the substrate. Sterol analyses indicated that cholesterol was the major dietary and larval sterol. HPLC/RIA data indicated that 20-hydroxyecdysone was the major molting hormone.     

Status of biological control by egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae) in citrus in Florida and Puerto Rico

Eggs of Diaprepes abbreviatus (L.) were routinely monitored in citrus groves at ten locations in Florida during 1997 and 1998 to study egg parasitism. One citrus location was studied in Puerto Rico. No native parasitoids were recovered from 1,337 D. abbreviatus egg masses studied in Florida citrus. In contrast, an average of 35.5% (range 12.5 to 68.8%) parasitism of egg masses was reported in Puerto Rico. The parasitoids Aprostocetus gala, Horismenus spp, and Quadrastichus haitiensis were recovered from the eggs of D. abbreviatusfstudied in Puerto Rico. The Horismenus parasitoids were suspected hyperparasitoids. Releases of the parasitoid Ceratogramma etiennei from Guadeloupe were initiated during 1998 at each of the Florida research sites. By the end of 1998, C. etiennei had been recovered from D. abbreviatus eggs at two of nine locations in Florida citrus. The parasitoid was recovered from 1 of 34 egg masses at one of these locations during the month of September and from 3 of 34 egg masses at the other location during the month of November. Whether or not C. etiennei establishes itself at one or more locations in Florida remains to be seen.     

Larval growth of Diaprepes abbreviatus (Coleoptera: Curculionidae) and resulting root injury to three citrus varieties in two soil types

Larval growth and intraspecific competition of Diaprepes abbreviatus (L.) larvae and consequent root injury in container-grown citrus in the greenhouse were evaluated. Roots of Carrizo citrange, Citrus sinesis L. Osbeck x Poncirus trifoliata (L.) Raf.; Cleopatra mandarin, C. reticulata Blanco, and Swingle citrumelo, C. paradisi Macf. x P. trifoliata (L.) Raf. rootstock seedlings grown in Candler fine sand and potting soil were colonized with different populations of D. abbreviatus larvae. Larvae were exposed to the seedlings for 79 d. Larval growth and development increased steadily for approximately 70 d on all rootstock-soil combinations, at which time most larvae were instars 6-8. Most feeding injury occurred to roots when larvae were between instars 3 and 6. Larval weight reached a plateau at approximately 70 d, but often declined between 70 and 79 d. When larvae were small, injury to seedlings developed slowly, primarily on fibrous roots, then feeding increased rapidly, often resulting in total consumption of both fibrous root and bark tissue. Although not statistically significant, root injury developed slightly slower on Swingle citrumelo compared with Carrizo and Cleopatra rootstocks, but damage was comparable by 79 d. Little or no difference in consumptive benefit to the larvae was found between the rootstocks. Based on larval weight days, little feeding injury occurred during the first 21 d, but increased rapidly between 21 and 60 d. Soil type affected the rate of larval growth and development, with potting soil contributing to greater growth rates. Detritus in potting soil provided little or no nutritional resource, suggesting that the effect of potting soil on larval development was primarily physical. In addition, fewer inoculated larvae per seedling exhibited greater weight gains than higher infestation densities, suggesting that intraspecific competition for nutritional resources influenced larval development.     

Abundance of Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) neonates falling to the soil under tree canopies in Florida citrus groves

The purpose of these experiments was to estimate the number and distribution of Diaprepes abbreviatus (L.) neonate larvae dropping from the canopy of infested citrus trees. The number of neonates was monitored in the field using passive funnel traps in two simultaneous experiments and a separate experiment for an additional year. In one experiment, traps were placed from trunk to dripline in the cardinal directions under each of five trees (132 traps total). In a second experiment, eight traps were placed under each tree in the cardinal directions, one trap 30 cm from the trunk and one trap 30 cm from the dripline/direction for 25 trees (200 traps total). Larvae were collected weekly for 50 wk in conical tubes containing ethylene glycol as a preservative. Traps closer to the tree trunk captured more larvae than traps nearer the dripline. The area under the tree canopy was positively correlated with the total estimated number of larvae captured per tree. The estimated number of total larvae/tree over the course of our experiments ranged from 955 to 7,290. The highest number of neonate larvae observed in 1 wk was 67 +/- 6/m2. There was an inverse relationship between the number of traps beneath a tree and the number of trees that needed to be sampled to estimate mean population density with a given precision. However, there was a direct relationship between number of traps/tree and the total number of traps needed for a given precision. This passive technique could be used to quantify the destructive larval stage and to assess D. abbreviatus management strategies.     

Reproductive biology of Fidiobia dominica (Hymenoptera: Platygastridae), an egg parasitoid of Diaprepes abbreviatus (Coleoptera: Curculionidae)

The reproductive biology of Fidiobia dominica Evans (Hymenoptera: Platygastridae) was studied in the laboratory (25.6 +/- 1 degrees C) using host eggs of Diaprepes abbreviatus L. (Coleoptera: Curculionidae). F. dominica readily parasitized D. abbreviatus eggs on both host plant and wax paper substrates. The number of egg masses parasitized and the number of offspring produced were higher when females were offered more than one host egg mass but did not differ when either two or three egg masses were offered. Female parasitoids that were provided with host eggs and a honey food source lived significantly longer than those that were not provided a food source; however, they did not parasitize more D. abbreviatus eggs. Oviposition occurred in host eggs from 0 to 7 d old, and host mortality was relatively consistent for eggs 0-5 d old and lower for eggs 6-7 d old. Successful parasitoid emergence seldom occurred after host eggs were 4 d old, and by 7 d, no adults successfully emerged. Developmental time from egg to adult was 19.3 +/- 0.2 d for males, significantly more rapid than the females (20.4 +/- 0.1 d). The mean longevity of adult females was 8.0 +/- 0.4 d, with a mean oviposition period of 2.7 +/- 0.3 d; males survived 8.1 +/- 0.4 d. The demographic parameters including intrinsic rate of increase (r(m)), generation time (T), and net reproduction (R(o)) were 0.142/d, 22 d, and 22.4 female eggs/d, respectively.     

Storage proteins of the larval root weevil Diaprepes abbreviatus (Coleoptera: Curculionidae): riboflavin binding and subunit isolation.

Proteins present at high concentrations in hemolymph of the larval weevil Diaprepes abbreviatus were previously shown to bind a synthetic coumarin, 7-amino-3-phenyl coumarin (coumarin-10). One of the two native proteins previously identified (protein I) is now shown to separate into two distinct bands (proteins Ia and Ib) using native gradient pore-limiting electrophoresis. The high concentration of proteins Ia, Ib, and II in larval hemolymph, their disappearance from hemolymph upon pupation, and an apparent hexameric structure shown by chemical crosslinking identify them as hexameric storage proteins (hexamerins). At least one chromatographic form of Ib isolated by anion exchange HPLC is now shown to bind riboflavin (Rb). Binding was also demonstrated by quenching of Rb fluorescence by a partially isolated mixture of the storage proteins. Lipophorin did not quench Rb fluorescence. Rb was heat-extracted from whole hemolymph and identified by its fluorescence spectra and by reverse phase HPLC with fluorescence detection. The two subunits shared by the three holoproteins have been isolated by sequential density gradient ultracentrifugation, gel permeation HPLC, and reverse phase HPLC. All three holoproteins shared the alpha subunit (M(r) 75,000), while the beta subunit (M(r) 71,000) was lacking from one of the three. Repeated passage through an anion exchange column yielded two of the three proteins (Ib and II) in homogeneous form. Chemical crosslinking with dimethylsuberimidate indicated a hexameric structure for the holoproteins. All subunits and holoproteins stained as high mannose glycoproteins when probed with biotinylated concanavalin A on PVDF membranes. The alpha subunit was high in Met, His, and Thr, and the beta subunit was high in Lys. Both were high in Pro and had approximately 16% Phe+Tyr. Sequences of the 20 N-terminal amino acid residues of each subunit showed 45-60% homology between subunits. These coleopteran proteins also showed some sequential homology but no immunological cross-reactivity with storage proteins from the lepidopterans Galleria mellonella and Heliothis virescens.     

Mitochondrial nucleotide variability in invasive populations of the root weevil Diaprepes abbreviatus (Coleoptera: Curculionidae) of Florida and preliminary assessment of Diaprepes sp. from Dominica

Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) is a root weevil introduced into the United States from the Caribbean in 1964. It is associated with >300 plants, including citrus, sugarcane, and potatoes. D. abbreviatus is widespread in Florida, and it has recently been detected in limited areas of California and Texas. The purpose of this research is to evaluate the utility of 16S ribosomal (16S rRNA) and cytochrome oxidase I (COI) mitochondrial markers for the delineation of genetic populations of D. abbreviatus in Florida and for the characterization of patterns of dispersion among these populations. We also assessed these markers as genetic tools for the clarification of taxonomic uncertainties in specimens from Dominica (Lesser Antilles). We analyzed 111 weevils from six Florida populations and six specimens from Dominica. In Florida, we found three haplotypes with only one haplotype in each population. Florida haplotypes differed by one to three nucleotide substitutions, possibly the result of a recent divergence from one source population or three different introductions from closely related populations from the Caribbean. In contrast, specimens from Dominica showed a high genetic variability with three 16S haplotypes and six unique COI haplotypes, delineating two mitochondrial clades. We show that these mitochondrial markers are useful for phylogeographic studies of D. abbreviatus.     

Effect of neem seed extract on feeding,growth, survival,and reproduction of Diaprepes abbreviatus (Coleoptera: Curculionidae)

A commercially available neem seed extract, Neemix 4.5, containing 4.5% azadirachtin (AZA), was assessed for biological activity against the root weevil Diaprepes abbreviatus (L.), an important exotic insect pest of Florida citrus. Laboratory bioassays against neonatal and 3-wk-old larvae fed sliced carrot treated with Neemix produced dose-dependent larval mortality and reduced fresh weights among survivors of treatments. The weight response was greater than the mortality response for both larval age groups. Neonates treated with 45 mg/liter AZA weighed 60% less than those in the control after 4 wk. Three-week-old larvae treated with 45 mg/ liter AZA weighed 30% less than those in the control after 5 wk. When neonates were exposed to insect diet incorporated with Neemix, reductions in larval survival and weight were observed at concentrations as low as 4.8 mg/liter AZA after 6 wk. Larval growth was inhibited by >97% with 42.9 mg/liter AZA in the diet. A soil drench containing 30 mg/liter AZA reduced the survival and weight gain of neonates added to potted citrus and provided protection to the roots in a greenhouse experiment. A concentration of 90 mg/liter AZA was required to provide protection of citrus roots against 4-wk-old larvae. Reproductive effects were observed when adult weevils were fed foliage treated with Neemix. The numbers of larvae hatching per egg mass were reduced by 27% and 68% at 30 and 90 mg/liter AZA, respectively. These results suggest that Neemix should be further evaluated for use in integrated pest management (IPM) programs of citrus.     

Steinernema diaprepesi n. sp. (Rhabditida: Steinernematidae), a Parasite of the Citrus Root Weevil Diaprepes abbreviatus (L) (Coleoptera: Curculionidae)

A nematode collected from Diaprepes abbreviatus is identified and described as a new species, Steinernema diaprepesi n. sp. The new species is closely related to S. feltiae, S. glaseri, and S. oregonense and can be distinguished from these species by the following characteristics: Males: Spicule averaging 79 (71-90) µm and spicule shape; D% (distance from anterior end to excretory pore/ esophagus length × 100) about 80; the ratio SW (spicule length/anal body width) about 1.8. Females: Vulva with short, double- flapped epiptygma; tail terminus usually with 5 papillae-like structures. Infective juveniles: Body averaging 1,002 (880-1,133) µm, EP (distance from anterior end to excretory pore) = 74 (66-83) µm; tail length = 83 (65-91) µm, and E% (EP/tail length × 100) = 89.6 (78-114). Lateral field pattern variable, the formula for the arrangement of ridges from head to tail is: 2, 6, 7, 8, 4, 2. The portion with eight ridges is the longest. This new species can be differentiated further from three closest species (S. feltiae, S. glaseri, and S. oregonense) by characteristic sequences of their ITS regions, including sequence lengths, ratios of similarity, composition, and differences in base characters in sequence alignment.     

Toxicity and repellency of Tephrosia candida to larval and adult Diaprepes root weevil (Coleoptera: Curculionidae)

Leaves of the tropical legume Tephrosia candida DC deterred feeding by adults of the Diaprepes root weevil, Diaprepes abbreviatus (L.), compared with leaves of Citrus macrophylla Wester, a common citrus rootstock, or T. vogelii Hook. f. When larvae were placed in pots containing plants of the three species for 28 d in a growth chamber, larval survival and weight gain were significantly reduced in pots containing plants of T. candida compared with larvae in pots with C. macrophylla or T. vogelii. Diet incorporation of lyophilized roots of T. candida into an artificial diet increasingly inhibited the growth of larvae and increased larval mortality with increased concentration of roots, whereas roots from C. macrophylla or T. vogelii had no effect compared with the diet-only control. T. candida, but not T. vogelii, contains at least one constituent that acts as an antifeedant toward adult D. abbreviatus and as a toxicant toward larvae. No antifeedant effect of roots of T. candida toward larvae was observed in no-choice pot tests or in a diet incorporation bioassay. In pots, larval feeding damage to roots of T. candida was evident. In the diet incorporation assay, 97% of larvae survived 29 d on a diet of cellulose powder (a nutritionally inert filler) despite losing weight. We conclude that decreased survival and weight gain of larvae-fed fresh or lyophilized roots of T. candida were the result of ingestion of a toxicant and not deterrence from feeding.     

Thermal requirements of Fidiobia dominica (Hymenoptera: Platygastridae) and Haeckeliania sperata (Hymenoptera: Trichogrammatidae), two exotic egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Diaprepes abbreviatus is an exotic root weevil occurring in southern US. It is a highly polyphagous species which can complete its entire life cycle on citrus and several woody ornamental plants. The lack of native egg parasitoids for this weevil in citrus orchards has triggered efforts to evaluate candidate egg parasitoids from the Caribbean Region into Florida. The egg parasitoids Fidiobia dominica and Haeckeliania sperata are two exotic natural enemies of D. abbreviatus recently introduced in the US in a classical biological control program. The thermal requirements of both parasitoids were studied in the laboratory. The upper development threshold (UDT) of F. dominica was 30.0°C, its maximal development rate (MDR) occurred at 27.6°C, its lower development threshold (LDT) was 9.6°C and its thermal constant (K) for development from egg to adult was 293.1 DD. For H. sperata, UDT was 35.0°C, MDR occurred at 31.0°C, LDT was around 15°C and K was 188.1 DD. Based on these results, both species would be able to complete 17 to 18 generations annually in southern Florida. However, host availability during critical periods could severely impair the ability of these egg parasitoids to establish and successfully control D. abbreviatus in areas where winter temperatures fluctuate around 12°C, the LDT for this pest.     

Discovery and characterization of chemical signals for citrus root weevil, Diaprepes abbreviatus

The tropical root weevil Diaprepes abbreviatus (L. 1758) (Coleoptera: Curculionidae) is a polyphagous insect from the Caribbean Islands and an invasive insect in the southern part of the United States where it is pest of citrus crops and ornamental trees. Adults feed upon foliage where aggregation, mating and oviposition take place. Here, the headspace volatiles from Citrus macrophylla Wester (Rutaceae), D. abbreviatus adults feeding on this plant, adults alone and adult feces, were collected by aeration and solid-phase microextraction (SPME) for analysis by gas chromatography-linked mass spectrometry (GC-MS). Electrophysiological responses of weevil antennal receptors to volatile headspace extracts and synthetic analogues were recorded by gas chromatography-linked electroantennographic detection (GC-EAD) and electroantennograms (EAGs). Antennal responses were recorded to the monoterpenes (R)-(−)-linalool, citronellal, nerol, citral, and geraniol; all present in the headspace of C. macrophylla. Antennal responses were also recorded to carvacrol, present in the headspace of adults and adult feces. The green leaf volatiles cis-3-hexen-1-ol and trans-2-hexen-1-ol, produced by other host plants, elicited reliable responses on the D. abbreviatus antenna. When comparing EAGs between (±)-linalool and (R)-(−)-linalool, no significant difference was found; responses to (R)-(+)-citronellal were larger than for (S)-(−)-citronellal. Among the individual compounds and blends tested using an open T-track dual choice olfactometer, only the blend of (±)-linalool, cis-3-hexen-1-ol and carvacrol (source dose 25:25:2.5 μg) elicited significant attraction of females, the same blend was repellent for males. The biologically active compounds found here likely play a role in host finding by D. abbreviatus and other interactions of the insect with its hostplant. Handling editor: Sam Cook     

Effect of root feeding by Diaprepes abbreviatus (Coleoptera: Curculionidae) larvae on leaf gas exchange and growth of three ornamental tree species

Diaprepes abbreviatus L. (Coleoptera: Curculionidae), feeds on a variety of ornamental plants grown in southern Florida. Studies were conducted to evaluate the effects of root feeding by D. abbreviatus larvae on leaf gas exchange and growth of three ornamental tree species commonly grown in southern Florida that are known hosts of this weevil: green buttonwood, Conocarpus erectus L.; live oak, Quercus virginiana Mill.; and pygmy date palm, Phoenix roebelenii O'Brien. These hosts were grown in containers and infested with weevil larvae. Net CO2 assimilation, transpiration, and stomatal conductance of CO, were measured monthly. Leaf, stem, and root fresh and dry weights of each species also were determined. In one of two tests, larval root feeding significantly reduced net CO2 assimilation, transpiration, and stomatal conductance of CO2 of infested green buttonwood trees. Leaf gas exchange of live oak was not affected by larval infestation. In addition to testing cumulative effects of multiple infestations of larvae, the effects of incremental infestations on leaf gas exchange and fresh and dry weights also were tested for each plant species. Net CO2 assimilation, transpiration, stomatal conductance of CO2, and dry weights of green buttonwood were reduced as a result of larval root feeding, whereas there was no effect of incremental larval infestations on leaf gas exchange of live oak or pygmy date palm within the experimental time frame. There was no effect of incremental larval infestations on dry weights of live oak, but leaf, stem, and dry root weight of pygmy date palm were lower for infested plants than for noninfested plants. Overall, green buttonwood was more susceptible to larval root feeding damage than either live oak or pygmy date palm.     

Distribution and abundance of three species of Sitona (Coleoptera: Curculionidae) in grassland in England

The distribution and abundance of weevils of the genus Sitona was assessed at 16 sites in England. The sites were chosen to cover a wide range of geographical and agricultural regions. Adult weevils were sampled on four occasions, from May to August 1993. Numbers of adults, larvae and pupae were determined for each site on four occasions from June to September 1994. Numbers of larvae declined throughout the year in which they were sampled and pupae were most numerous in July. The population density of adults increased through the sampling period in both years. Sites close to pulse crops had the largest population levels of weevils, with Sitona lineatus L. the dominant species. No differences in the population levels of Sitona hispidulus (F.) or S. flauescens (Marsh.) were detected. Evidently populations of the latter two species are fairly constant in grassland and most of the variation in the population densities of these three species found in English grassland can be attributed to the migratory behaviour of S. lineatus and the proximity of pulse crops.     

Weevils Lixinae (Coleoptera,Curculionidae) as gall formers

Galls induced by six species of Lixinae weevils from Ukrainian steppes are described. The gall formation by Larinus species is doubtful. One gall may in some cases be jointly occupied by different weevil species. The adaptive significance of gall formation in Lixinae is discussed.