Lennart Ågren

Flagellar sensilla of some colletidae (Hymenoptera: Apoidea)

Abstract The distribution and surface structures of the flagellar sensilla and setae of Colletes cunicularius (L.), C. similis Schenck and Prosopis communis (Nylander) are described. Sensilla found are: s. ampullacea, s. basiconica, s. campaniformia, s. coeloconica, s. placodea, s. trichodea A, B, C and D, and also several forms of setae. Colletes males, especially C. cunicularius, are characterized by a dense population of s. trichodea A, whereas Prosopis has sparser and more slender ones. Prosopis has fewer sensilla than Colletes in general, and fewer pit organs. The females of Prosopis have a band of s. trichodea C or D in most segments in the pore plate field. In a general comparison of females and males, the former have more s. trichodea B, especially on the tip of the antenna, and also more pit organs. Males lack s. basiconica. In both genera an area on the ventral side of the terminal segment has very few sensilla.

Flagellar sensilla of two species of Andrena (hymenoptera: Andrenidae)

Abstract The flagellar sensilla of both sexes of Andrena tibialis and A. vaga were surveyed by scanning electron microscope (SEM). The first flagellar segment is very long in both sexes of A. vaga and in females of A. tibialis . The females of both species have abundant s. basiconica, which males lack. Other sensilla found in both males and females were s. placodea, s. campaniformia, s. trichodea (of at least 3 types) and pit organs. Setae are also numerous.

Identification and electroantennographic activity of sex-specific geranyl esters in an abdominal gland of femaleAgriotes obscurus (L.) andA. lineatus (L.) (Coleoptera, Elateridae)

Both geranyl hexanoate and geranyl octanoate were identified by GC/MS as the major volatiles in a hitherto uncharacterized abdominal gland in females inAgriotes obscurus. Only geranyl octanoate was found inA. lineatus. In EAG tests performed onA. obscurus males, geranyl butanoate and geranyl hexanoate elicited the strongest antennal responses.

Architecture of a lamellicorn flagellum (Phyllopertha horticola, Scarabaeidae, Coleoptera, Insecta)

The distal three of the seven flagellar segments of the scarabaeid beetle Phyllopertha horticola are lamelliform, gathered into a club, and possess five sensillar fields that are packed with sensilla placodea. The most proximal surface of the club bears only hair‐shaped sensilla. On the inner four sensillar fields a narrow central elongated zone houses pit organs and cavities with sunken sensilla placodea and other sensilla. The most distal, fifth sensillar field is smooth. The sensilla placodea seem to be of several types. The only distinct difference between the sexes is the shorter and more rounded lamellae of the female. The total count of sensilla placodea in males outnumbers that of the females by about 60%.

Form-specific fragances fromOphrys insectifera L. (Orchidaceae) attract species of different pollinator genera. Evidence of sympatric speciation?

Two closely related forms ofOphrys insectifera were observed in the field to attract different pollinator species selectively.O. i. ssp.insectifera attracted males of two species ofArgogorytes (Sphecidae, Hymenoptera Aculeata) andO. i. ssp.aymoninii attractedAndrena combinata males (Andrenidae, Apoidea, Hymenoptera Aculeata). A third form,O. aff.i. ssp.insectifera, attracted none of these three species. Volatile compounds from flowers and inflorescences of the three forms (originating from Öland, Sweden, and Aveyron, France) were collected, using entrainment, enfleurage, and solvent extraction techniques, and identified by gas chromatography — mass spectrometry. Scent differences between the three forms were confirmed in the amounts of aliphatic hydrocarbons (C11–C19), methyl esters (C14–C18), short chain aliphatic 1-alcohols (C6–C12), and monoterpene alcohols (C10).

Andrena wilkella male bees discriminate between enantiomers of cephalic secretion components.

Diastereomers of the spiroacetal, 2,8-dimethyl-1,7-dioxaspiro [5.5]undecane, represent main components of the cephalic secretion from males of the solitary bee,Andrena wilkella. The major compound proved to be of high enantiomeric purity, showing (2S,6R,8S) configuration. Only the naturally occurring enantiomer attracted patrolling males in the field; its antipode was behaviorally inactive and in a racemic mixture did not inhibit response. The (E,Z) diastereomers were also found to be almost inactive. EAG studies gave the same result as the behavioral tests. The biological function of the spiroacetal is discussed in view of the evolution of the mating behavior inA. wilkella.

Flagellar Sensilla of Sphecodes Bees (Hymenoptera, Halictidae)

The antenna of Sphecodes bees were investigated as regards the type and distribution of the sensilla. Eleven species originating from Sweden were used. Totally 325 specimens were studied. The distribution of sensilla placodea and sensilla trichodea on the antennal segments were studied in the light stereomicroscope. One to three antennae per species were also examined by SEM. The following types of sensilla were found: s. placodea; pit organs; s. campaniformia; s. basiconica; s. trichodea A, B and CD; and setae. The distribution of sensilla, especially s. placodea and s. trichodea A, was found to be species‐specific in the male sex and their diagnostic value in taxonomy is stressed. In the female sex no specific characteristics were found, although two groups could be distinguished.

Flagellar sensillum patterns in Nyssoninae and Philanthinae wasps (Hymenoptera, Sphecidae)

Morphology and distributional patterns of antenna1 sensilla were compared between four species in three genera of Sphecidae. Sensilla placodea have plates that are raised to resemble low domes in Argogorytes mystaceus and A. fargei or low pegs in Bembix rostrata and Cerceris rybyensis. Sensilla basiconica occur in both sexes of Bembix and Cerceris, but, similarly to Apidae (s. laf.), only in females of Argogorytes. The antennae of the two species of Argogorytes differ primarily in being larger in A. mysfaceus, thus permitting space for more sensilla. In Bembix rostrata, the male antennae are adapted to function as ‘gripping’ organs.