Composition of the Labial Gland Secretion of the Bumblebee Males Bombus pomorum

Labial gland secretions of 22 males of the bumblebee Bombus pomorum , collected in the Czech Republic, were analysed separately for each individual. The secretions contained 70 compounds among which saturated and unsaturated hydrocarbons strongly dominated. The proportion of hydrocarbons in the secretion was unusually high (85-100% ) compared to other bumblebee species studied so far (3-15%). Methyl and ethyl esters of fatty acids, known from many other bumblebee species, formed only minor components (less than 1 % in sum) of the secretions of several B. pomorum individuals. No terpenic compounds, typical for males’ marking secretion of many bumblebee species, were detected in B. pomorum . The absolute quantities of hydrocarbons present in the labial gland extracts were comparable with those usually present in other species. The composition of hydrocarbons found in the labial glands was different from the profile of the cuticular hydrocarbons. Despite our expectations in species exhibiting a regular patrolling and scent-marking behaviour, the labial gland extracts obtained from B. pom orum males were unusually low concentrated and their chemical composition was atypical with respect of the proportions of hydrocarbons when compared with other patrolling species. This is the first report on the analysis of the labial gland secretion of the B. pomorum males.

Analysis of the Labial Gland Secretion of the Cuckoo-Bumblebee (Psithyrus vestalis) Males and Synthesis of Abundant Geranylcitronellol

Labial glands of the cuckoo-bumblebee males of the species Psithyrus vestalis were extracted and the components of their secretions were identified. Chemical composition of the males' signal of Psithyrus vestalis has not yet been described in the literature. We found geranycitronellyl acetate to be the main component (48%). Geranylcitronellol and (Z)-15-eicosen-1-ol were present in the secretion in lower amounts. Long-chain aldehydes, acetates, and hydrocarbons formed only minor components of the mixture. The identification of minor components was based on GC-MS, while the more abundant compounds were isolated and fully characterized by spectral and chemical methods. For the structure confirmation, geranylcitronellol was prepared from geranyl bromide via a three-step synthesis.

The physiology of wandering behaviour in Manduca sexta. I. Temporal organization and the influence of the internal and external environments

A stereotyped series of behavioural changes occurs in preparation for pupation in Manduca sexta. Feeding declines over an 8-h period, after which the larva coats its body with a labial gland secretion. The animal then begins a 10- to 30-h wandering behaviour during which it constructs a pupation chamber underground. Wandering behaviour starts during a specific temporal gate which is determined by an internal circadian timer. The scotophase of the day prior to wandering has the major influence on the timing of internal processes which activate the behaviour. Wandering duration is correlated with larval size, reflecting a possible influence of juvenile hormone. The larva appears to be irrevocably committed to begin wandering by an event that occurs about 15 h previously, a time that corresponds to the second of three prothoracicotropic hormone (PTTH) pulses and the accompanying elevation of ecdysteroids as measured by Gilbert et al. (1981). We conclude that both the initiation and duration of wandering behaviour are governed primarily by processes which are internal to the larva.