Amorbia, Clemens, 1860

Phillips-Rodríguez, Eugenie & Powell, Jerry A., 2007, Phylogenetic relationships, systematics, and biology of the species of Amorbia Clemens (Lepidoptera: Tortricidae: Sparganothini)., Zootaxa 1670 (1670), pp. 1-109 : 49-50

BIOLOGY OF AMORBIA

Seasonal Life History

Most of the Amorbia species distributed in the lowlands or middle elevations in the neotropics apparently fly throughout the year. For species not recorded in every month, collection records suggest activity over several months including dry and rainy seasons in Central America, indicating they are probably multivoltine. Species that occur in Mexico at elevations above 1700 m (i.e., A. potosiana , A. chiapas , and A. laterculana ) are recorded from May to November, with a single record from February for A. laterculana . Not enough data are available to generalize voltinism in these species.

Adult activity in the three northernmost Amorbia species , A. humerosana , A. cuneana , and A. knudsoni , is limited by winter conditions. A humerosana has been collected from March through September, and there is one record in Florida in December. The few records available for A. knudsoni are from May to August. Although the pooled records for A. cuneana show activity in every month of the year, observations on flight activity recorded by Powell in Berkeley, California, over twenty years clearly demonstrate two defined generations, one from April to July and a second from late August to December. According to data presented by Brown & Bash (2000) this bivoltine cycle is not defined in southern California (San Diego County), where they recorded A. cuneana in every month of the year. No diapause occurred in any stage of the species we reared. According to Chapman & Lienk (1971), A. humerosana overwinters in the pupal stage.

ADULT. Most of the specimens examined were collected at light, and we assume that all Amorbia adults are nocturnal. Oviposition by females in laboratory rearings usually took place at night. Females laid eggs in oval or rounded patches in an imbricate pattern and covered them with an opaque colleterial fluid. Confined females laid one to three egg patches within one or three nights. Field records on oviposition behavior are scattered. According to Zimmerman (1978), females of A. emigratella usually deposited their eggs on the upper surface of the leaf. On Santa Cruz Island, California, Powell found two large, oval patches of A. cuneana eggs on Lyonothamnus floribundus (JAP 00E50) deposited on the upper surface of the leaves. Females of A. humerosana lay the eggs on the upper surface of apple leaves ( Chapman & Lienk, 1971). Observations made on confined females suggest that they prefer smooth surfaces for oviposition.

All species of Amorbia have a small proboscis that appears to be functional. Confined individuals require a water source and die within 24 hours if water is not available. We did not provide other nutrition, such as honey solution, which presumably would have increased fecundity.

IMMATURE STAGES. Information on the early stages of Amorbia is based on the literature and larval and pupal specimens obtained for the following species: A. revolutana , A. humerosana (from one larval specimen), A. cuneana , A. osmotris , A. cacao , A. nuptana (eggs to adults, no larvae preserved), A. exustana , A. emigratella , A. rectangularis , A. rhombobasis , A. monteverde , and A. eccopta . Details are given under each species.

EGG. Amorbia eggs are laid in patches covered with a colleterial fluid that dries opaque whitish. This covering is characteristic of all Sparganothini but it is transparent in most genera. The eggs are dark green, light green, or olive green. In laboratory rearings, the eggs usually were laid in small patches of 20-40 or bigger patches of 50- 83 eggs per patch. In general, females deposit large patches first, followed by successively smaller ones (Powell, unpublished data), and it is likely that females we collected at lights had already deposited their largest egg masses. According to Zimmerman (1978), A. emigratella females lay patches of 65- 120 eggs per cluster. Incubation is temperature dependent, and the time required for most of the species reared in laboratory was from 8 to 12 days. In A. exustana and A. rectangularis the larvae hatched after an average of 19 days.

LARVA. Larvae are greenish when feeding on host plants with the head amber to rust brown or orange. They are leafrollers or leaftiers and concealed feeders. In general, all larvae have a dark genal band on the head, usually over the stemmata and extending posteriorly. The thoracic shield is usually pale with dark bands of varying width bordering the shield laterally and sometimes posteriorly. In A. rhombobasis the head and thoracic shield are entirely dark brown. Development time for species feeding on synthetic diet at room temperature (from eggs to adults) was of 7-10 weeks, with the shortest developmental time in A. rectangularis and the longest in A. cuneana .

MacKay (1962) gave a detailed description of the larvae of four species of Amorbia : A. humerosana , A. emigratella , A. cuneana , and A. essigana (now treated as a synonym of A. cuneana ). She stated that Amorbia could be distinguished by a few characters: position of the V1 setae on A9 about twice as far apart as those on A8; the dorsal and subdorsal pinacula on meso- and metathorax elongated posteriorly; the anal shield strongly tapered, and the anal setae unusually long. We examined the distance ratio of V1 on A9 versus V1 on A 8 in other Amorbia species and found no consistent pattern. In A. eccopta and A. monteverde the distance between the V1 setae on A9 is 1.5 to 2.5X the distance on A8. In contrast in A. osmotris , A. rhombobasis , and A. revolutana , the setae are separated by the same distance on A8 and A9. The anal comb is well developed in all the species except A. revolutana ( Figs. 113–131).

Host Plant Associations

Field collections of larvae and acceptance of synthetic diet by all Amorbia species tested indicate that most if not all Amorbia are polyphagous. We gathered information on preferences for host plants in seven species of Amorbia (Appendix III). The species for which the most information is available are A. humerosana , A. emigratella , and A. cuneana (pest species). Records for these three species include 40 plant species belonging to 23 different families. Polyphagy in the genus also is inferred by lab studies in which most species have been reared using synthetic diet. Avocado, guava, orange, and several species of Pinaceae are examples of host plants upon which some Amorbia species have become pests of actual or potential economic importance.

Pupa. Pupation usually takes place within a moderately dense cocoon woven between the leaves of the host plants. The pupa is typically tortricine without conspicuous sculpturing, except abdominal dorsal pit are evident in some species ( Fig. 118); all species have a well developed cremaster.

Parasitoids. Actia interrupta Curran (Tachinidae) was reported as an occasional parasitoid on Amorbia cuneana in Central California ( Powell, 1964). In Costa Rica we obtained Phytodietus maximoi Gauld ( Ichneumonidae : Tryphoninae : Phytodietini ) from a larva of A. osmotris feeding on Rubus sp. Zimmerman (1978) reports several parasitoids on A. emigratella in Hawaii: Bracon omiodivorum (Terry) (Braconidae) , Brachymeria obscurata (Walker) (Chalcididae) , Echthromorpha sp. (Fabricius) ( Ichneumonidae ) Ephialtes hawaiiensis (Cameron) (Ichneumonidae) and Trichogramma minutumm Riley (Trichogrammatidae) .