Over 50 genera of bees release pollen from flower anthers using thoracic vibrations, a phenomenon known as buzz-pollination. The efficiency of this process is directly affected by the mechanical properties of the buzzes, namely the duration, amplitude, and frequency. Nonetheless, although the effects of the former two properties are well described, the role of buzz frequency on pollen release remains unclear. Furthermore, nearly all of the existing studies describing vibrational properties of natural buzz-pollination are limited to bumblebees (Bombus) and carpenter bees (Xylocopa) constraining our current understanding of this behavior and its evolution. Therefore, we attempted to minimize this shortcoming by testing whether flower anthers exhibit optimal frequency for pollen release and whether bees tune their buzzes to match these (optimal) frequencies. If true, certain frequencies will trigger more pollen release and lighter bees will reach buzz frequencies closer to this optimum to compensate their smaller buzz amplitudes. Two strategies were used to test these hypotheses: (i) the use of (artificial) vibrational playbacks in a broad range of buzz frequencies and amplitudes to assess pollen release by tomato plants (Solanum lycopersicum L.) and (ii) the recording of natural buzzes of Neotropical bees visiting tomato plants during pollination. The playback experiment indicates that although buzz frequency does affect pollen release, no optimal frequency exists for that. In addition, the recorded results of natural buzz-pollination reveal that buzz frequencies vary with bee genera and are not correlated with body size. Therefore, neither bees nor plants are tuned to optimal pollen release frequencies. Bee frequency of buzz-pollination is a likely consequence of the insect flight machinery adapted to reach higher accelerations, while flower plant response to buzz-pollination is the likely result of its pollen granular properties.

Insects have evolved a great diversity of sound-producing mechanisms largely attributable to their hardened exoskeleton, which can be rubbed, vibrated or tapped against different substrates to produce acoustic signals. However, sound production by forced air, while common in vertebrates, is poorly understood in insects. We report on a caterpillar that 'vocalizes' by forcing air into and out of its gut. When disturbed, larvae of the Nessus sphinx hawkmoth (Sphingidae: ) produce sound trains comprising a stereotyped pattern of long (370 ms) followed by multiple short-duration (23 ms) units. Sounds are emitted from the oral cavity, as confirmed by close-up videos and comparing sound amplitudes at different body regions. Numerical models using measurements of the caterpillar foregut were constructed to test hypotheses explaining sound production. We propose that sound is generated by ring vortices created as air flows through the orifice between two foregut chambers (crop and oesophagus), a mechanism analogous to a whistling kettle. As air flows past the orifice, certain sound frequencies are amplified by a Helmholtz resonator effect of the oesophagus chamber. Long sound units occur during inflation, while short sound units occur during deflation. Several other insects have been reported to produce sounds by forced air, but the aeroacoustic mechanisms of such sounds remain elusive. Our results provide evidence for this mechanism by showing that caterpillars employ mechanisms similar to rocket engines to produce sounds.

Susceptible female weevils prefer larger (and heavier) males to mate, a trait associated with deltamethrin resistance, favouring the maintenance and spread of the resistant phenotype in the population. © 2016 Society of Chemical Industry.

Larval competition is particularly prevalent among grain beetles that remain within their mother-selected grain throughout development, and the behavioral process of competition is usually inferred by the competition outcome. The Mexican bean weevil Zabrotes subfasciatus (Boheman) is subjected to resource availability variation because of the diversity of common bean types and sizes, from small (e.g., kidney beans) to large (e.g., cranberry beans). The competition process was identified in the Mexican bean weevil reared on kidney and cranberry beans by inference from the competition outcome and by direct observation through digital X-ray imaging. Increased larval density negatively affected adult emergence in kidney beans and reduced adult body mass in both kidney and cranberry beans. Developmental time was faster in cranberry beans. The results allowed for increased larval fitness (i.e., higher larval biomass produced per grain), with larval density reaching a maximum plateau >5 hatched larvae per kidney bean, whereas in cranberry beans, larval fitness linearly increased with density to 13 hatched larvae per bean. These results, together with X-ray imaging without evidence of direct aggressive interaction among larvae, indicate scramble competition, with multiple larvae emerging per grain. However, higher reproductive output was detected for adults from lower density competition with better performance on cranberry beans. Larger populations and fitter adults are expected in intermediate larval densities primarily in cranberry beans where grain losses should be greater.