Defensive volatile secretions of two diplopod species attract the carrion ball roller scarab <Emphasis Type="Italic">Canthon morsei</Emphasis> (Coleoptera: Scarabaeidae)

Summary. We report field and laboratory evidence indicating that the defensive compounds secreted by the millipedes Amplinus bitumidus (Diplopoda: Polydesmida) and Anadenobolus putealis (Diplopoda: Spirobolida) attract the carrion scarab Canthon morsei (Scarabaeidae: Scarabaeinae). In a Mexican tropical rain forest, C. morsei was mostly caught in pitfall traps baited with the carcasses of both millipede species. Only a few beetles were attracted to fish carrion. Experimental evidence indicates that C. morsei is attracted to freshly dead millipedes. Benzaldehyde and HCN were identified from Amplinus bitumidus; but 2-methyl-1,4-benzoquinone (toluquinone) and 2-methoxy- 3-methyl-1,4-benzoquinone from Anadenobolus putealis. Benzaldehyde attracted significantly more C. morsei individuals than fish meat, or millipedes of both species did after rinsing in hexane. This is the first report of Polydesmida attracting dung beetles.     

Sperm competition and evidence of sperm fertilization patterns in the carrion ball-roller beetle Canthon cyanellus cyanellus LeConte (Scarabaeidae: Scarabaeinae)

Field observation and laboratory experiments were conducted to investigate sperm competition and patterns of sperm fertilization under different experimental conditions in the carrion ball-roller beetle Canthon cyanellus cyanellus. Males in nature can mate with females whose spermathecae contains fertile sperm from other males. Sperm precedence was investigated using a visible genetic marker. The progeny of red (homozygous recessive) virgin females mated once with a red male and afterward, once with a green beetle (homozygous dominant) and vice versa, revealed that regardless of its color, the last male to mate fertilized c.a. 50% of the eggs, suggesting strong sperm competition. Males were able to achieve higher levels of paternity (more than 80%) when mated ad libitum with previously mated females, although large amount of variance in paternity does not exclude the possibility of first male sperm precedence or female cryptic choice. These results suggest that repeated mating and sperm replacement are the mechanisms by which last males achieve sperm precedence.     

Behavioral and antennal electrophysiological responses of a predator ant to the pygidial gland secretions of two species of Neotropical dung roller beetles

The pygidial gland secretions of Neotropical dung roller beetles appear to function as defensive agents against predator ants. Behavioral and electrophysiological tests were used to evaluate the responses of the ant Camponotus sericeiventris to pygidial compounds secreted by the dung roller beetles Canthon cyanellus cyanellus and Canthon femoralis femoralis (Coleoptera: Scarabaeidae). Our behavioral investigation revealed a lower aggressive response of C. sericeiventris to the dung roller beetles compared to their response to the fly Anastrepha ludens. Additionally, C. sericeiventris workers attacked C. f. femoralis more often than C. c. cyanellus. The behavioral aggression of C. sericeiventris was greater toward male than female C. c. cyanellus. Electroantennography showed that the antennae of C. sericeiventris react to pygidial extracts from C. c. cyanellus and C. f. femoralis. Three compounds from male and female C. f. femoralis and C. c. cyanellus elicited coupled gas chromatography-electroantennogram (GC-EAD) activity in the antennae of C. sericeiventris. Geraniol and an unknown compound (A) were specific for C. f. femoralis, whereas guaiacol and another unknown compound (B) were specific to C. c. cyanellus; phenol was shared by both beetle species. This is the first report confirming that the pygidial gland secretions of dung roller beetles play a role in their defense against predators.