Labial glands

The major work on the labial gland pheromones has been done on bumble bees, namely 25 species in Bombus and Psithyrus. From the cephalic extracts, these 

It should be noted that the compounds listed in Table 14.2 were assumed to come from labial glands, but this has been verified only in several species. Some of the compounds, identified in head extracts, could be from mandibular glands. (See discussion of Bombus mandibular glands.) 

Bombus B. agrorum B. callumanus B. cingulatus B. derhamellus B. hortorium B. hypnorum B. jonellus B. lapidarius B. lapponicus (blond) B. lapponicus (dark) 

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Bumblebee males mark objects on their flight paths with secretions from the labial glands [ 126,127]. Although these marks can be attractive to both males and virgin queens, and are chemically well characterized in several species, the specific components responsible for attraction remain unknown. 

Agren L., Cederberg B. and Swensson B. G. (1979) Changes with age in ultrastructure and content of male labial glands in some bumblebee species (Hymenoptera, Apidae). Zoon. 7 1-14. 

Katzav-Gozansky T., Soroker V., Ionescu A., Robinson G. E. and Hefetz A. (2001b) Task-related chemical analysis of labial gland volatile secretion in worker honeybees (Apis mellifera ligustica). J. Chem. Ecol. 27, 919-926. 

Territorial Pheromones. Males of many species of bumblebees mark selected sites with labial gland products that attract both males and females. These territorial mating spots are "perfumed" with a wide variety of acyclic compounds that appear... 

Figure 2, HPLC of i.-ascorbic acid from insect tissues (65). A, L,-ascor-bic acid, 1.7 fxg B, M. sexta hemolymph (0.01 mL) extract C, M. sexta labial gland extract, 1.4 mg wet weight.

The titer of L-ascorbic acid in tissues was examined during development. During the fifth instar, L-ascorbate increased about eightyfold in the labial gland and ten-fold in the hemolymph, where millimolar levels were measured (Figure 3). Regression analysis of the tissue kinetics revealed that the labial gland accumulated L-ascorbic acid about twice... 

Figure 3. Changes in the content of L-ascorhic acid in hemolymph and labial gland during larval development of M. sexta (65). A, Hemolymph regression analysis yielded line defined as larval weight = 6.5 [ascorbic acid] at a = 0.01 level and = 0.83 B, labial gland regression analysis yielded line defined as larval weight = 12.7 [ascorbic aM] at a = 0.01...

I I. Mouth placed between first pair of mouthparts 12. Labial glands... 

SvENSsoN, B. G. and G. Bergstrom, Volatile marking secretions from the labial gland of north European Pyrobombus D. T. males (Hymenoptera, Apidae), Insectes Sociaux, 24, 213-224 (1977). 

In this connection it should be mentioned that also certain animals are able to produce plant hormones. Larvae of the moth Stigmella argentipedella, living as mining caterpillars in birch leaves (Betula verrucosa) excrete cytokinins (E 3.1) from their labial glands. The released cyto-... 

Larval parasitoids respond to silk, frass, volatiles, cuticular components, and glandular secretions (Weseloh, 1981). For example, Cardiochiles nigriceps responds to hydrocarbons in the mandibular glands of H. virescens (Vinson, 1968), Apanteles melanoscelus responds to the silk produced in labial glands of gypsy moth (Weseloh, 1977), and several species respond to host feces. 

Table 14.2 Volatile components identified in the cephalic (labial) gland extracts of bumble bees... 

The chemistry of mandibular gland secretions has been studied in two genera of Anthophorinae. Batra and Hefetz (1979) showed that the secretions of male Melissodes denticulata are dominated by a homologous series of saturated and unsaturated butanoates ranging from C,2 to Cjs (even carbon compounds only). However, none of these compounds has been detected in female head extracts, so that it is possible that the chemicals actually came from the cephalic labial glands, which are better developed in males. In contrast, the secretions of... 

The chemistry of the cephalic secretions of bumble bees needs clarification. Cederberg (1977) reports geraniol from the mandibular glands while Kullenberg et al. (1970), and Svensson and Bergstrdm (1977) report geraniol from male labial gland extracts. Similarly, citronellol has been reported from both sources. 

Fig. 16.19 (a) Soldier of Macrotermes carbonarius showing position of the hyper-tophied labial gland 0>lack) and reservoir (stippled) (after Maschwitz et al., 1972) (b) Soldier of Macrotermes subhyalinus showing the position of the frontal gland (stippled) and fontanelle (after Prestwich et al., 1977). 

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