Behavioral response of Lygus hesperus to conspecifics and headspace volatiles of alfalfa in a Y-tube olfactometer.

The western tarnished plant bug, Lygus hesperus Knight, feeds and develops on a variety of weeds in the spring, with later generations moving to alfalfa and cotton where severe damage to reproductive structures can occur. A synthetic attractant for monitoring or mass-trapping L. hesperus, or the identification of potential attractants for natural enemies, would be useful tools for integrated pest management programs. Studies investigated the response of naive and experienced fifth-instar and adult L. hesperus to odors associated with conspecifics and alfalfa, Medicago sativa L. Fifth-instar L. hesperus responded to all plant/insect combinations, whereas female L. hesperus only responded preferentially to vegetative and flowering alfalfa where conspecifics had fed for 24-72 hr, and to vegetative alfalfa where conspecifics were added approximately 30 min before the test began. Males were not attracted to headspace volatiles from any of the alfalfa treatments. Analysis of headspace volatiles showed that (E)-2-hexanal, (Z)-3-hexen-l-ol, alpha-pinene, (Z)-3-hexenyl acetate, (E)-2-hexenyl acetate, limonene, (Z)-ocimene, (E)-beta-ocimene, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (E, E)-alpha-farnesene are emitted from both vegetative and flowering alfalfa. Indole and (3E, 7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene were only detected in flowering alfalfa. Damage to alfalfa by L. hesperus increased emissions of (Z)-ocimene, (E)-beta-ocimene, (E)-beta-caryophyllene, and (E, E)-alpha-farnesene, while beta-pinene, myrcene, methyl salicylate, and (3E, 7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene were only detected from damaged plants. Thus, individual or mixtures of these alfalfa volatiles may be useful as attractants for capturing nymphs and adult females of L. hesperus in the field.

Histological examination of flight muscle development and breakdown in Bemisia tabaci (Homoptera: Aleyrodidae): Relationship to age and flight behvior.

Bemisia tabaci exhibited their longest flights between 3 and 5 days following adult eclosion. They rarely engaged in flight when they were < 4 hr old and were only capable of short-duration flights after day 7. This difference in flight capacity appears to be associated with changes in the flight musculature and mitochondria. Myofibrils and mitochondria accounted for approximately 50% and 33% of the area within the flight muscles, respectively. These two elements, however, varied with the age and sex of the whitefly. The percentage of the total area occupied by myofibrils was lower in 9-day-old males relative to females and all other age categories. Sarcomere length decreased in older whiteflies, regardless of the sex. Myofibril diameter did not vary with the age of the whitefly, but the diameter of female whitefly myofibrils was greater than the diameter of male whitefly myofibrils. The number of myosin filaments within a myofibril unit increased with age, peaking at 5 days of age for females and 7 days of age for males. In all age groups, females had more myosin filaments than were found in males. Changes in mitochondria and levels of glycogen were related to the observed differences in flight activity. The area occupied by mitochondria was small in < 4-h-old and 9-day-old whiteflies, and mitochondrial cristae were undeveloped in newly emerged whiteflies. In 7- and 9-day-old whiteflies the cristae began to separate, leaving visible spaces within the mitochondria. Glycogen granules were abundant in the flight musculature of newly emerged (< 4-hr-old), 1-day-old and 3-day-old whiteflies, but by 5 days of age only 25% of whiteflies contained glycogen granules. Seven- and 9-day-old whiteflies contained no visible glycogen. An examination of the flight muscle of whiteflies after flights of varying duration (up to 60 min) revealed no relationships between flight duration and the number of mitochondria or the percentage of the total area occupied by mitochondria. There was, however, a positive relationship between flight duration and the percentage of total area occupied by myofibrils. © 1995 Wiley-Liss, Inc.

Effects of larval nutrition on the host-seeking behavior of adult Aedes aegypti mosquitoes.

Adult female Aedes aegypti that were reared on a suboptimal diet as larvae were less likely to engage in host-seeking behavior than were adults derived from larvae reared on an optimal diet. A postemergence carbohydrate diet of either 1 or 10% sucrose solution did not affect this response. When the progeny of field-collected Aedes vexans were reared in the laboratory, the adults were significantly larger than their parents. This indicated that the larvae of the field population were not as adequately nourished as their laboratory-reared progeny.