Tortricid Moth

The Tortricidae are one of the largest families of the so-called micro-lepidoptera. Though worldwide in distribution, the family is more strongly represented in temperate and tropical upland regions then in the lowland tropics and probably reaches its greatest diversity in the moss forests of tropical latitudes. The family is of great economical importance: the larvae of many representatives cause major economic damage in agriculture, horticulture and forestry on a wide variety of crops including pomes and stone fruits, citrus fruits, grapes, ornamental crops, tea, coffee, cereals and cotton. In forestry, many species of both coniferous and deciduous trees are attacked by the pest species. They are sometimes commonly called "bell moths" by the British. Their resting posture is said to resemble a church bell.

tortricid moth

Many Tortricid larvae spin their cocoons incorporating a plant's rolled or folded leaf.Order Lepidoptera: Moths. Unlike the butterflies, moths are usually nocturnal. Many moths and their caterpillars are major agricultural pests in large parts of the world. Moths in the family Tineidae are commonly regarded as pests because their larvae eat fabrics, clothes and blankets made from natural fibers such as wool or silk. Moths in the genus Farinalis feed on stored grain, flour, corn meal and other milled grain products. Butterflies Main Moths Moths Index Butterflies Index Custom Search Red Planet Inc. North American Insects & Spiders

The introduced apple tortrix, Archips fuscocupreanus, is a pest of fruit trees and other woody plants. This eastern Asian tortricid moth entered North America before 1982 although it was not positively identified until 1995. In Japan and Korea, this tortrix or leafroller is a major pest of apple. In certain areas of Japan, it has developed resistance to insecticides. In the Northeast, the apple tortrix inhabits mainly coastal counties in Massachusetts, Rhode Island, Connecticut, New York, and New Jersey. It also occurs in coastal areas of Washington State.

Life Cycle and Appearance: The apple tortrix has one generation per year, spending the winter as an egg in a black egg mass on a tree branch or trunk. The caterpillars hatch from the circular egg mass (1/8" by 1/4") probably in late April. They feed upon foliage, flowers, or developing fruits, often binding these same plant parts together to form a shelter. The caterpillars complete their growth by late May or early June at which time they are grayish green with an orange or brownish orange head and a black thoracic shield behind the head. When they are full-grown, they are 3/4-7/8" in length. The caterpillars form pupae in folded leaves or under the loose bark of tree trunks or in debris near trees. The reddish brown adult moths, which have a wingspan of 3/4-1", emerge 1-2 weeks after pupation Between mid-June and mid-July, the females lay eggs in black masses on the large branches and trunks of trees. The eggs remain dormant until the following spring.

Gustation in the mouthparts of adult insects is generally found in the galeae, in the maxillary palps of the maxilla, and in the labial palps of the labium. The labial palps of insects with standard chewing mouthparts (e.g., Coleoptera, Orthopteroids) are usually small and bear gustatory sensilla6,7,8. In insects with mouthpart modified for sucking and licking (e.g., Diptera, Hemiptera), the labium and associated labial palps retain their taste function9,10,11,12. In Lepidoptera, the galeae have joined in a long and coiled proboscis, and in most lineages the rest of the mouthparts structures are largely reduced, except for the labial palps, which are relatively large and cover most of the front part of the insect head at each side of the proboscis13. The labial palps of Lepidoptera present a cavity at the tip of the apical segment, the labial-palp pit organ (LPO), which contains sensilla that respond to changes in CO2 concentration14. A ventral glomerulus in the antennal lobe receives the input of the CO2 sensory cells. CO2 detection may help Lepidoptera in host-plant selection14. In some moth species, the labial palps bear chaetica-like sensilla15,16, which often have a gustatory function in other insect appendages3,4,5. The presence of putative gustatory receptors of the sugar clade in the labial palps of Helicoverpa armigera (Hübner)17 further indicates the presence of gustation in the labial palps, but as far as we know, there is no physiological evidence that the labial palps of Lepidoptera have a gustatory function. The antennae of Lepidoptera are well known for their olfactory function performed by numerous sensilla trichoidea, but they also bear some gustatory sensilla chaetica in each flagellum2. In noctuid moths the gustatory function of antennal sensilla chaetica has been demonstrated18,19,20. The gustatory function of sensilla chaetica on the antennae of tortricid moths21,22,23 remains to be shown.

The objective of this study is to determine if the sensilla present of the surface of the labial palp of moths respond to gustatory stimuli. To this end we performed electrophysiological recordings from adults of three tortricid moths, Cydia pomonella (L.), Lobesia botrana (Denis and Shiffermüller) and Grapholita molesta (Busck), which are key pest species of fruit trees and vines worldwide24,25. Two sugars (fructose and sucrose) and two salts (KCl and NaCl) were tested at 3 concentrations. In addition, we tested the response of sensilla chaetica in the antennae. In order to determine the biological relevance of sugars in these species we also studied their effect on the adult longevity.

We present evidence that the labial palps of moths have a gustatory function. Furthermore, we found significant differences between appendages, stimuli, species and sexes. As far as we know, this may be the first direct evidence that the labial palps of moths, or perhaps any Lepidoptera, have a gustatory function, while it is a common feature in other insect orders. The presence of a flexible socket at the base of the sensilla chaetica suggests mechanosensory function3,4, however observations should be conducted to confirm this role. We do not know the extent of gustation in the labial palps of Lepidoptera because reports of uniporous sensilla chaetica (i.e., with a putative gustatory function) on the external part of labial palps are scarce. Chaetica-like sensilla with a terminal pore have been reported in a species of the Cossidae family16. Sensilla chaetica are described in other Cossidae and in members of the Tortricidae and Pyralidae families, but it is not indicated if they bear a pore at the tip, and thus they may not be gustative15,26,27. In a Neopseustidae specie, aporous sensilla chaetica have been described28. Several studies on members of the Gelechiidae, Pyralidae, Sphingidae, Noctuidae, Plutellidae, Erebidae and Nymphalidae families fail to report sensilla chaetica or any other type of sensilla with a putative gustatory function in the labial palps29,30,31,32,33,34,35,36,37,38.

Sugars and salts play a role on the fitness and behavior of the three tortricid moths. Our longevity test confirms that adults of the three species do not live long without water and that sugars prolong longevity41,42,43. When given access to flowers under laboratory conditions the longevity of C. pomonella increased with respect to a no-food control, but a dilution of sugar in water was even better than the flowers44. Peach extrafloral nectar, a natural solution rich in sugars45, enhanced G. molesta adult longevity42. Despite the importance of sugar on adult fitness, only L. botrana has been observed feeding in the wild. It visits the flowers of tansy (Tanacetum vulgare L.) (a non-host plant located around the vineyards) at dusk to feed on the pollen and nectar46. Sugars stimulate oviposition in C. pomonella and L. botrana47,48, and gustatory sensilla in the ovipositor of L. botrana detect fructose and sucrose48. KCl is also perceived by sensilla in the ovipositor of L. botrana, and it affects oviposition48. Sugars and salts could impact larval fitness too49,50,51. Therefore, the presence of taste receptors on antennae and palps could contribute to the detection of salts and sugars, but they may also be specialized on the detection of other stimuli not tested yet.

There are few reports on the putative behaviors where Lepidoptera may use the gustatory sensilla detected on the labial palps. Grant54 observed the response of the tortricid moth Choristoneura fumiferana (Clemens) to a rubber septum loaded with female sex pheromone. The tips of the labial palps contacted with the septum ("the palps themselves pulled away from the head in lever-like fashion") right before attempting copulation (Fig. 1 in54). Also during courtship, G. molesta males and females perform a dance where there is mutual contact with the antennae and probably the palps too55. Thus, gustatory receptors on palp and antennae may be used to detect conspecific signals, such as cuticular hydrocarbons, which often present sexual dimorphism in insects56,57. Gustatory function of the labial palps may also be related to oviposition choice behavior because in the moth Cactoblastis cactorum (Berg) females actively touch the plant with the labial palps while searching for oviposition sites58.

The discovery of gustation in the labial palps of moths may shed new light on the innervation of the labial palp nerves in the moth brain. Unilateral palp backfills typically reveal bilateral projections ascending to the antennal lobe where they stain a basal glomerulus, equivalent in both males and females, the "labial pit organ glomerulus" (LPOG)33,59,60. This glomerulus receives the input from the CO2 sensory neurons housed in the labial pit organ. However, palp backfills show additional arborizations in the suboesophageal ganglion (SOG)33,59. To clarify this point, Pramod et al.60 performed selective mass staining from both, the inside of the labial pit organ and the outer surface of the distal labial palp segment of H. armigera and compared their arborizations. LPO sensory neurons projected exclusively to the LPOG, whereas the non-LPO sensory neurons targeted the gnathal ganglion and the ventral nerve cord. It is very likely that the axons that do not innervate the LPOG correspond to mechano/gustatory neurons located on gustatory sensilla because the mechano/gustatory input from other cephalic appendages ends in the SOG2,3. Interestingly, an SEM picture of the labial palp of H. armigera does not show sensilla chaetica33. Sensilla chaetica are rather conspicuous and resilient61 so it is unlikely that they are accidentally knocked off when scales were removed to observe the palps. If they did not fall during scale removal, then other type of sensilla may contain the palp neurons that innervate the SOG. Thus, further studies are required to determine which other Lepidoptera species have gustatory function in the labial palps. 041b061a72