Omar Bailez

Life-history of the guava weevil, Conotrachelus psidii Marshall (Coleoptera: Curculionidae), under laboratory conditions

The guava weevil, Conotrachelus psidii Marshall, is a severe pest of guava fruits in Brazil. The mated females lay eggs in small unripe fruits. As the fruits develop, so do the larvae. Mature larvae abandon the ripe fruits and pupate underground. Larval feeding causes extensive damage to the fruit. We conducted this study to understand the weevil biology under laboratory conditions. Weevil-infested ripe guava were collected in orchards and placed inside cages with moist sand. After emergence, the adults were individually placed in acrylic boxes with food and water. Recently emerged adults were also placed inside plastic boxes for mating, after which the females were isolated. The eggs were placed on moist filter paper in petri dishes containing slices of ripe guava fruit. Egg-hatching was monitored daily and the number of larval instars established by measuring the width of their head capsules. The egg incubation period lasted 3.9 ± 0.58 days. The larval period was 16.0 ± 3.80 days and four instars were identified. After burrowing in the soil, the mature larvae (pre-pupa) remained underground for 142.0 ± 32.00 days and then pupated. The pupal period lasted 16.0 ± 0.90 days, but the adults remained underground for a further 34.0 ± 18.00 days. After emerging from the soil, adults lived 148.0 ± 89.00 days. Fecundity varied from 539 to 793 eggs/female, and the percent egg hatch was 96.5%.

Mechanism of host recognition in Neodohrniphora elongata (Brown) (Diptera: Phoridae).

Insects can use different cues derived from their host or habitat to localize and identify an appropriate host. We conducted this study to investigate the mechanisms used by Neodohrniphora elongata (Brown) to localize and recognize the host Atta sexdens rubropilosa Forel. Females of the parasitoid N. elongata were collected in the field and tested individually in an observation box. The effect of chemical and visual stimuli, associated with A. sexdens rubropilosa, on the location and acceptance behaviour of N. elongata was verified. The chemical stimuli of the ant workers alone triggered no behavioural response in the phorid. Visual stimuli of the ant were sufficient to trigger behavioural acts related to host localization and recognition in the phorids. The trail pheromone of A. sexdens rubropilosa associated with host visualization increased the total time of inspection of a potential host. Visual cues in motion increased the inspection period, compared to static visual cues. Moving basic morphological configurations, regardless of the degree of complexity, triggered similar inspection behaviour as that observed towards live hosts in N. elongata. The phorids, however, did not identify these incomplete morphological models as hosts when static.

Dimorfismo sexual do gorgulho-da-goiaba Conotrachelus psidii Marshall (Coleoptera: Curculionidae)

Este trabalho teve como objetivo determinar diferencas que permitam identificar o sexo de adultos de Conotrachelus psidii Marshall, 1922. Gorgulhos coletados em um pomar comercial de goiaba foram individualizados em caixas e mantidos em laboratorio. Diariamente, dez gorgulhos eram agrupados e seu comportamento observado. Durante o acasalamento, os machos e as femeas eram identificados. Cinquenta gorgulhos de cada sexo foram sacrificados e observados sob microscopio estereoscopico. Foram examinadas a insercao da antena no rostro e a distribuicao de pilosidade na superficie do torax e abdome. Tambem, foi medido o comprimento e a largura do corpo, pronoto, ultimo esternito abdominal e rostro. Do ponto de vista comportamental, machos emitem sons por estridulacao enquanto que as femeas nao. A largura do corpo, do pronoto e o comprimento do corpo e do rostro nas femeas foram maiores, enquanto que a largura do ultimo esternito abdominal foi menor. Tres outras diferencas morfologicas sao visiveis a olho nu: 1) A regiao anterior do pronoto das femeas possui pilosidade reduzida ou ausente enquanto que nos machos e abundante; 2) o ultimo tergito nas femeas fica recoberto pelo penultimo enquanto que nos machos e parcialmente visivel; 3) o primeiro esternito abdominal nas femeas e mais proeminente, convexo e com pilosidade reduzida ou ausente. Nos machos esse segmento e ligeiramente concavo e com pilosidade em toda a superficie. As diferencas entre machos e femeas encontradas neste trabalho permitem, sem danificar os insetos nem alterar seu comportamento, uma sexagem eficiente do gorgulho-da-goiaba.

Caste polymorphism of apterous line of the Neotropical termite Nasutitermes corniger (Motschulsky) (Isoptera, Termitidae)

Termite societies are structured by individuals that can be grouped into castes and instars. The development of these instars in most species occurs in irregular patterns and sometimes is distinguished subcastes in physical systems that originate polymorphic soldiers and workers. In this study, we characterized the morphological diversity of castes of apterous in Nasutitermes corniger. We collected four colonies of N. corniger, one every three months between May 2011 and February 2012. Individuals of the nest were separated into groups: larval stages, workers and presoldiers and soldiers. A morphometric analysis was performed on individuals from each group based on head width, metatibia, antenna, and thorax length. The data were submitted to discriminant analysis to confirm different morphological types inside these groups. The apterous line of N. corniger is composed of one first larval instar and two second larval instar. The workers caste has two lines of development with four instars in a larger line and three instars in a lower line. Two morphological types were identified in presoldiers and soldiers. The pattern of castes was similar to other species of the genus, in which bifurcation into two lines of workers, one smaller and one larger occurs after the first molt.

Behavioral responses of the arboreal termite Nasutitermes corniger (Isoptera: Termitidae) to wood extracts

The termite Nasutitermes corniger is attracted to weathered wood, but it is not known whether this attraction is of chemical or physical nature. This work examines whether wood extracts can change the attraction of N. corniger to a food substrate. In a first experiment, filter paper impregnated with a eucalyptus extract, Eucalyptus grandis, and another one with a solvent were placed in the foraging arena of N. corniger nests under laboratory conditions. The extracts used were from weathered or unweathered wood. During the second experiment, two tests were performed using eucalyptus wood. First, a piece of unweathered wood was impregnated with an extract of weathered wood (treatment) or solvent (control). In the second test, a piece of weathered wood was impregnated with an extract of unweathered wood (treatment) and another one with solvent (control). At the end of the tests, the number of termite recruitment on each substrate was quantified. Filter paper recruited more termites when treated with unweathered wood extracts or with extracts of weathered wood than when impregnated with the solvent. Unweathered wood treated with extracts of weathered wood recruited more termites than the control. However, weathered wood impregnated with extracts of unweathered wood recruited similar numbers of termites as the same wood impregnated with the solvent. It was verified that chemicals from weathered or unweathered wood increased the foraging activity of N. corniger in neutral substrates, but only chemicals from weathered wood altered the attraction of N. corniger to eucalyptus wood.

Mechanism of Trail Following by the Arboreal Termite Nasutitermes corniger (Isoptera: Termitidae)

In this study, we investigated the mechanisms used by the arboreal termite Nasutitermes corniger (Motschulsky, 1855) to follow trails from the nest to sources of food. A plate containing one of seven trail types was used to connect an artificial nest of N. corniger with an artificial foraging arena. The trail types were: termite trail; paraffined termite trail; trail made of paraffin; rectal fluid extract trail; sternal gland extract trail; feces extract trail; and solvent trail (control). In each test, the time was recorded from the start of the test until the occurrence of trail following, at which point the number of termites that followed the trail for least 5 cm in the first 3 min of observation was recorded. The delay for termites initiating trail following along the termite trail was lower (0.55 ± 0.16 min) than in the trails of sternal gland extract (1.05 ± 0.08 min) and trails of termite feces extract (1.57 ± 0.21 min) (F2, 48 = 22.59, P < 0.001). The number of termites that followed the termite trail was greater (207.3 ± 17.3) than the number that followed the trail of termite feces extract (102.5 ± 9.4) or sternal gland extract (36, 9 ± 1.6) (F2, 48 = 174.34, P < 0.001). Therefore, feces on the trail may play an important role alongside sternal gland pheromones in increasing the persistence of the trail.