D. Klimetzek

Dosage response to ethanol mediates host selection by “secondary” bark beetles

common one responded mainly to Z 9 14:OAc, a second type to Z7+ 14: OAc with a weak response also to Z 9 14:OAc, and a third type responded exclusively to Z11-14: OAc (Fig. 2). The medial shorter sensilla towards the antennal axis have two cells: Cell A with a high spike amplitude and cell B with a low spike amplitude. The A cell responds to totally different pheromone components than the cells in the marginal long sensilla: the majority (82%) responds to Z5-14: OAc, whereas a lower number (18%) is activated exclusively by Z7-12:OAc (Fig. 2). The function of the B cell is still unknown. It did not respond to any of the compounds tested. These results were corroborated by measuring the response of ten short sensilla to the same compounds with the penetration technique [81. The receptor types found by us are thus in agreement with what Priesner reported [6]. The proportion of sensillacontaining cells sensitive to compounds other than Z5and Z9-14:OAc is striking. Trapping experiments by Priesner [6] showed that these other compounds have an inhibitory effect on the attraction of male A. exctarnationis. Our own unpublished gas chromatographic analyses on capillary columns did not reveal traces of any of them in female extracts (<0 .5% of Z5 14:OAc). They are, thus, most probably pheromone compounds in some other competing species. More interestingly, however, we found a clearcut correlation between the morphology of individual sensilla, their spatial localization, and their sensitivity to different compounds. The receptors for the pheromone component z g 1 4 : O A c are exclusively arranged along the lateral margins of the antennal segments, and are each innervated by one neuron. The Z 5-14:OAc receptors are all placed medially in sensilla containing also a second cell. Such a spatial arrangement of receptors sensitive to different pheromone components has not been reported before. It is interesting to note that Z 9 14: OAc is perceived by a specific cell in the long distal sensilla placed on the edge of the male A. exclarnationis antennal segments. There is in the pheromone blend an optimal proportion of this component to Z5-14: OAc of less than 10% for male attraction. The proportion of molecules perceived by the sensilla from the air is by aerodynamic laws much higher for distal sensilla than for central ones [9]. This means that the localization of the Z 9 t 4 : OAc receptors on the male A. exclamationis antenna could be adaptive for sensitive detection of the m i n o r o n e of the two pheromone components. Received November 25, 1985 and January 10, 1986

Chirality of insect pheromones: Response interruption by inactive antipodes

(-)-disparlure, or both enantiomers [1] resulted in distinctly different response patterns by the nun moth and the gypsy moth (Fig. 1). With the nun moth, response to the traps increased with the concentration of(+)-disparlure regardless of the addition of(-)-disparlure (Table 1) which is known to drastically suppress gypsy-moth response at r~/cemic or higher concentrations [1]. Tests using traps baited with (-)-disparlure only ted to conflicting results. No moths were caught in two areas but large numbers in another [4]. Our findings are well in accordance with observations which indicate that nun moths respond to increasing concentrations of racemic disparlure while gypsy moths do so to a lesser degree [5]. One possible explanation of this phenomenon rests, indeed, with chiral differences in pheromone production between the two species [6]. Hypothetically, P. dispar would be expected to produce the (+)-enantiomer only, while P. monacha might produce both optical antipodes of the disparlure.

Disparlure: Differences in pheromone perception between gypsy moth and nun moth

nothing fashion with carefully controlled stimulus intensities (Fig. I c). Small changes in snprathreshold intensities can be accompanied by abrupt changes in the shape of the short-latency potential (Fig, 1 d). They are understood as combined action potentials of two large axons. Separation between the spikes of two large axons was found in some preparations where stimulus and recording site were far apart from each other indicating slightly different conduction velocities of the fibres (Fig. l c). These short-latency spikes are the largest electrical events recorded after electrical stimulation ipsior contralateral to the recording site. Spikes run equally well in both directions along the cord as expected for a through-running axon system. It is reasonable to attribute the described action potentials to the two giant fibres shown by morphology. The conduction velocity of the giant fibres was determined as 1.14 m/s (n=19) and fell in the range of 0.7 1.7 m/s. Giant-fibre responses can be produced by mechanical stimulation of the antennae, the dorsal parts of the head, the tail, the feet and dorsolateral body walls. The strongest phasic discharges of the giant fibres were obtained from touching the head or tail. The response shows rapid habituation. Contralateral response is prevented by cutting the commissures of the ladder-like-type nerve cord near the stimulus site. The animal displays different fast reactions when touched or pinched. One of them is a quick shortening of the body including several segments when the head or tail is stimulated. The contraction shortens the soft-body animal up to 65% of its former length in 200-500 ms. It is assumed that the activity of the giant fibres is associated with rapid overall body movements. The acquisition of a fast-conducting through-running giant-fibre system is a typical feature of many polysegmental invertebrates. The giant fibre system of Per# patoides shows considerable similarities to those of annelids with respect to morphology and function in relation to behavior (for comparison see [2]).

Das Pheromon-System des Waldreben-Borkenkäfers, Xylocleptes bispinus Duft. (Col., Scolytidae)

The pheromone system of Xylocleptes bispinus Duft. (Coleoptera, Scolytidae)

Das Pheromon‐System des Bunten Ulmenbastkäfers Pteleobius vittatus (F.) (Col., Scolytidae)

The pheromone system of the elm bark beetle Pteleobius vittatus (F.) (Col., Scolytidae)

Influence of weather and nest site on the nuptial flight of hill‐building wood‐ants of the Formica rufa‐group (Hym., Formicidae)

The production of alatae and nuptial flight of hill‐building wood‐ants of the Formica rufa‐group were studied from April to August 1992 on 1700 ha of forest near Freiburg. Winged ants were found in 28.7 % of the 331 nests examined (F. polyctena 27 %, F. rufa 27 %, F. lugubris 37 %, F. pratensis 48 %, F. truncorum 0 %). The likelihood of finding alatae rose with nest height and circumference; previous damage of the nest mound showed no negative effects. Of the alatae‐nests, 26 % produced ♂♂ only; 38 % ♂♂ + ♀♀; 36 % ♀♀ only. The pure ♀♀‐nests were found in F. polyctena and F. rufa but not in the other species. The production of sexuals lasted 2.5 weeks in F. rufa, 3.7 weeks in F. polyctena, 4.3 weeks in F. lugubris, and 6.3 weeks in F. pratensis. Nests producing sexuals were predominantly found at lower altitudes, the first appearance of alatae was delayed by 1–4 weeks per 100 m increase in altitude. An exception occurred in some nests above 800 m probably due to the temperature inversion. Nuptial flight was recorded on 20 days; and on 5 of these days more than one ant species was swarming.