Pheromones play a prominent role in insect control as well as human attraction. The gypsy moth, Lymantria dispar(L.), was introduced into the U.S. in I869, when it was accidentally released in Massachusetts. By 1889, it had become a destructive pest that defoliated fruit and shade trees over an area of approximately 360 mi’ in that year with true pheromones. Thereafter it continued to spread throughout the Northeast.
In 1912, Congress passed the Plant Quarantine Law, which prevented the shipment of any insect life stage from infested to noninfested areas. Although there have been brief respites, the area infested and the amount of defoliation have continually increased. Between 1970 and 1975, about $8.5 million of timber and pulpwood were destroyed in Pennsylvania alone. By 1971, the moth had been found in all but three Maryland counties; by 1974, the insect’s range had increased to over 200,000 mi’ in the U.S. and Canada. Expenditures by the federal government to control the gypsy moth were over $110 million between 1970 and 1975, and expenditures by state governments were even greater. Nevertheless, it is expected that the moth will ultimately infest all the oak regions east of the Great Plains, which would have particularly serious consequences throughout the southern forests, where suitable hosts for the insect are abundant. It is not known whether a warmer climate would favor the production of a second generation of the insect each year, but it has been suggested that slower larval development would result, and this would prolong the destructive feeding period by using alarm pheromones according to http://infospeak.org/?p=128.
In fact, “more legislation and money have been used in attempts to control the gypsy moth than any other insect pest in the United States.”‘ The infestations are cyclical in nature; the insect population rises to a peak over a period of several years and may then undergo a rapid decline. This fluctuation makes it difficult to assess the effectiveness of control measures, especially when the control measures under study may also reduce populations of parasites and predators that play a role in reducing the moth population. Learn about top pheromones for men 2016.
Gay pheromones in humans have much of the opposite effect on insects. This is because insects do not have homosexual tendencies like people. Many insects are asexual and mate only for survival.
The frequency of pheromone contact between workers together with the continued movement of bees would seem to ensure that queen pheromone is adequately dispersed within the colony, particularly among the younger bees which are on the combs containing brood.
There is a greater frequency of pheromone contact in colonies with mated queens than in colonies with virgin queens, presumably reﬂecting the stimulatory effect of an increased queen pheromone level on worker activity. Virgin queens spend a much greater proportion of their time moving over the comb than do mated queens (Free et al., 1987a); because moving queens attract only small courts the amount of pheromone workers obtain from a mobile virgin must be reduced, even though the virgin queen’s own movement must aid its distribution to some extent. The fewer pheromone contacts made in colonies during the winter, or in colonies headed by failing queens, probably indicates the distribution of less queen pheromone (Free et al., 1987a).
Bees from the queen’s court, and the workers ﬁrst contacted by them on leaving the court, show an increased tendency to participate in food transfer, but the number of contacts involving food transfer are relatively few compared to those involving pheromone contact only, and bees from the court are as likely to receive food as to give it. When food transfer does occur it has the desirable effect of prolonging pheromone contact.
Bees that lick their queen subsequently make more reciprocated pheromone contacts than those that only palpate her with their antennae. This may be because such bees spend a longer time in the court, acquire a greater amount of queen pheromone, and are moreattractive to others. However, workers that lick a virgin queen show a pronounced tendency to engage in food transfer with other workers, so the possibility remains that some pheromone communication may occur during food transfer, but if so it usually occurs only in special circumstances and is in general of minor importance and incidental to pheromone transfer by pheromone contact.
Therefore it no longer seems likely that queen pheromone has a direct biochemical effect on worker bees after being ingested by them, but instead it seems probable that the queen’s presence is communicated by contact chemoperception, followed by appropriate worker behavioural responses or hormonal adjustments. It is possible that bees in the queen’s court are themselves stimulated to produce pheromones which induce a reciprocal release of pheromone by workers that contact them and this alone could be a means by which the queens presence is communicated without physical transfer of queen pheromone being necessary. However, the absence of contact other than between the antennae of the workers concerned makes this unlikely.
Pheromones and Life Stages
Life stages — The gypsy moth passes through four distinct stages: (1) the egg stage, (2) the larval stage, (3) the pupal stage, and (4) the adult stage. There is one generation each year. In the summer, shortly after the female mates, she deposits clusters (masses) of 100 to 800 eggs, covered with hairs from her body, in sheltered places such as under loose tree bark or under branches. The insect overwinters as an embryonated egg. The timing of eclosion in late spring depends on temperature and photoperiod, and hatching may occur over a period of several weeks in a single locality. It is the voracious feeding of the larvae on foliage that causes the damage. Since the larvae develop to a length of 4 to 6 cm at maturity, during the fifth and sixth instars they consume approximately 24 in.’ of foliage per day. Insecticidal control is normally applied during the larval stage. Learn about pheromones here.
In late June or early July the larvae reach maturity and pupation occurs. After a pupal stage of 10 to 14 days, the adult moth emerges. Reproduction is the only function of the adult moth. The female does not normally fly but remains close to the site of emergence and emits an attractant pheromone.
The male, which has well-developed antennae that are capable of detecting the airborne attractant pheromone, flies upwind and orients toward the source. Electroantennogram studies have indicated that there are antennal receptors for the optically active form of the attractant pheromone, (+ )- disparlure.‘