Diagnosis (from Mengual et al. 2009).
Face moderately to greatly produced anteriorly, with distinct tubercle; oral opening about 5 times as long as wide, with oral apex greatly extended beyond level of antennal base; antennal pits separate; plumula well developed; subscutellar pile fringe distinct, one or two rows of long pili; wing broadly bare basomedially, without apical dark macula; alula broad, about 1.5 times as broad as cell BM; metasternum pilose; abdomen broadly to narrowly elongate.
The adult and larva of Allograpta micrura Osten Sacken, 1877 (Diptera, Syrphidae) feed on pollen of Castilleja talamancensis Holmgren, 1978 (Scrophulariaceae) in the highlands of Costa Rica (Weng and Rotheray 2008).
Pupariation (from Weng and Rotheray 2008).
Larvae pupated 3-6 days after turning green which occurs towards the end of development (n = 7). Larvae appeared to search for a site to pupate. They moved rapidly, waving the anterior end from side to side and moved in this way for up to one day. During pupariation, an anal secretion adhered the puparium to the substrate. Puparial dimensions did not differ between sexes. Under laboratory conditions pupariation took place on the sides of plastic bags and other container walls, on small twigs, fresh leaves, within the flower or fruit calyx, and in debris. Larvae rarely remained on exposed branches to pupate. No puparia were found in the field despite intensive searching.
Coloration of puparia varied, apparently in accord with the color of the substrate; pupae in clear containers like transparent bags or Petri dishes were translucent white (n = 30), while pupae hidden in debris (n = 35) were brown (round dots to irregular patches). Pupal duration (n=35) ranged from 9 to 13 days under laboratory conditions, and the range was the same for specimens (n = 10) reared in a cooler (5 - 7 ºC).
Adult behaviour (from Weng and Rotheray 2008).
Females of A. micrura (n=8) were seen to fly repeatedly around racemes and land on the colorful bracts and other floral structures of C. talamancensis. Oviposition (observed twice) took place after more than twenty minutes of inspection of an inflorescence and nearby branches. Three of eight females captured on flowers in late September had their abdomens swollen with eggs. Both males and females frequently fed on open flowers of different species, such as Geranium guatemalensis and Valeriana spp. They also fed from more tubular flowers (i.e., Pernettya prostrata and Castilleja talamancensis) while hanging upside down from the ventral part of the flower, and using the long proboscis to take the pollen and nectar. Males and females with and without developed eggs fed on the same host plants. Males hovered in sunlight in open areas (trails) about 40 to 60 cm from C. talamancensis bushes (0.5-1.5 m above the ground). Females were seen resting on leaves and they fed on flowers located near hovering males. They flew slowly and very close to the bushes. On one occasion, a female passed rapidly in front of a hovering male and landed on an exposed branch. The male flew toward her and landed nearby. Mounting occurred immediately and copulation began shortly thereafter.
Allograpta (Fazia) micrura (Osten Sacken, 1877).
Osten Sacken, C.R. (1877) Western Diptera: Descriptions of new genera and species of Diptera from the region west of the Mississippi and especially from California. Bulletin of the United States Geological and Geographical Survey of the Territories 3, 189-354. [1877.04.30]
New description:
FEMALE.
Head: Face produced forward, oral margin anterior to antennal bases, with distinct facial tubercle, yellow with medial narrow black vitta joining frontal black area between the antennae, mainly yellow pilose with a sublateral vitta of black pile; gena yellow, yellow pilose; frons yellow with a medial broad black vitta, black pilose; vertical triangle black, black pilose; antenna vrown, basoflagellomere orange basally; occiput black, silver pollinose, whitish-yellow pilose with some black pile dorsally.
Thorax: Scutum black, bronze pollinose except anteriorly and laterally, yellow pilose; postpronotum yellow, yellow pilose; notopleuron yellow, yellow pilose; scutellum yellow with a diffuse medial brownish macula, black pilose, subscutellar fringe complete with black pile. Pleuron mostly black, except proepimeron yellow, posterior anepisternum yellow on posterior half, katepimeron partly yellow and katatergum yellow, and katepisternum with large dorsal yellow macula; anterior anepisternum bare; metasternum pilose; calypter yellow; plumula yellow; halter yellow; spiracular fringes yellow. Wing: Wing membrane hyaline; apically microtrichose, extensively bare basally with bare areas on cells R2+3 and R4+5 basally, cotal cell microtrichose only on apical fourth. Alula broad, microtrichose. Legs: Entirely yellow, tarsi brown and metatibia brownish. Metabasitarsomere elongate.
Abdomen: Parallel-sided, slightly oval, unmargined. Dorsum mainly black, black pilose except 1st tergum yellow pilose and 2nd tergum yellow pilose laterally on basal 1/2; 1st tergum yellow with black fascia on posterior margin; 2nd, 3rd and 4th terga black with medial yellow fascia, straight fascia in 2nd tergum and arcuate fascia on 3rd and 4th terga; 5th tergum black with four yellow vittate maculae.
From Weng and Rotheray (2008).
At study sites, adults of Polybia aequatorialis Zavatiari, 1906, a common social wasp (Vespidae), used an effective method for finding A. micura larvae within Castilleja flowers. Three wasps were observed inspecting inflorescences that had eggs attached to floral structures. They apparently detect the larva inside flowers and buds when they bite the flower structures. On one occasion, a wasp apparently detected a larva inside a flower, whereupon she cut the calyx and corolla with her mandibles and pulled out a third instar larva. The wasp subdued the larva by cutting it into two. It then chewed the cut sections to empty the gut contents of the prey which material was discarded. Finally it rolled the chewed each section of the larva into a spherical mass for transport back to the nest.
An unidentified species of Paracaratomus Ashmead,1894 (Pteromalidae) was the only parasitoid reared from larvae of A. micrura. Two early third instar syrphid larvae collected in July at the Estación Biológica Cerro de la Muerte pupated as usual in the laboratory, but wasps emerged from the puparium at its rounded proximal end 20 to 22 days later. The parasitoid likely oviposited in the early third instar, or before, but emergence is delayed until the host is in its puparium; this parasitoid is therefore a koinobiont.
Host plant (from Weng and Rotheray 2008).
Field observations revealed that larvae of A. micrura were associated with flowers of Castilleja talamancensis N. H. Holmgren 1978 (Scrophulariaceae). C. talamancensis is an endemic shrub about 0.3 -1.5 m tall growing in open or partially shaded sites in high mountain forests and paramo formations (2,600 - 3,200 m) and is limited to the Talamanca mountain range in Costa Rica (Barringer and Burger 2000). Flowering occurs all year round but peaks at the onset of the rainy season (April- May). The yellow flowers are on terminal racemes, 2-10 cm long with red and yellow bracts.
Nearctic species known from British Columbia south to California and Texas; and Mexico.
From Weng and Rotheray 2008.
A. micura eggs were found attached to the bracts of inflorescences, bud and flower calices and also occurred on the branches and the main rachis of C. talamancensis. Up to two eggs and four empty shells were found on a given raceme. Eggs and larvae were found on inflorescences of C. talamancensis from grouped bushes, solitary plants, and even on plants less than 30 cm tall bearing only one inflorescence.
Larvae were often encountered in the field chewing through the calyx and corolla of unopened flower buds and irregular-shaped holes in flowers were a sign that larvae were present. In one sample of 5 plants, just over half (57 %) of the 46 racemes bearing up to 15 buds, flowers or fruits were occupied by eggs and/or larva. Most larvae were located inside the corolla tube of buds and open flowers. Some first instar larvae were found feeding inside the anthers after having chewed through the thecae. A few individuals were found between the calyx and corolla and also within wilted flowers and developing fruits.
In open buds and flowers, larvae were either near the ovary, in the basal portion of the corolla, or feeding in anthers located in the distal portion of the flower. Larvae inside undeveloped buds were either in the narrow space close to the anthers, or inside the thecae. Usually, only one larva was found in each flower or fruit structure. On a few occasions, two larvae were found inhabiting the same flower structure. No larvae were observed outside of flowers in the field although in the laboratory, larvae moved to new flowers after pollen had been consumed.
Egg (from Weng and Rotheray 2008).
A uniform scale-like sculpture on the egg surface is visible under a dissecting microscope. This regular sculpture may contribute to the optical effect and also function as a hydrophobic surface (Endress 1994). Electron microscopy revealed a ridge-like structure at one end surroundingthe micropyle.
Third stage larva (from Weng and Rotheray 2008).
Overall appearance: A subcyclindrical, white to yellow larva generally turning green towards the end of the feeding stage with an inconspicuous sheet of whitish fat covering the hind gut; tapering anteriorly, truncate posteriorly; locomotory organs barely protruding and lacking pro legs and crochets; papillae bearing antennomaxillary organs subcyclindrical and appearing above the mouth; apex of head skeleton with labrum and labium pointed and distinctly upcurved; mandibles present as curved, brown sclerotised rods encased within fleshy, laterally flattened projections that appear at the lateral margins of the mouth and are attached to the base of the papillae supporting the antennomaxillary organs; posterior breathing tube longer than basally broad and bifurcated at apex; spiracular plates with 3 spiracular openings and ecdysial scar on apical margin.
Length 3.4-11 mm (n = 37); subcyclindrical in cross section, tapering anteriorly, truncate posteriorly. Dorsal and lateral sensilla accompanied by single apical setae and mounted on a projection about as long as apical setae. Pattern of segmental sensilla as for other syrphid larvae (Rotheray and Gilbert 1999).
Head: Antennomaxillary organs mounted on laterally flattened papillae that surround the lateral margins of the mouth. Head skeleton: Length 0.70 mm; arrangement similar to other syrphines (Hartley 1963; Roberts 1970), i.e. labrum and labium elongate and equally produced at the apex of the head skeleton, which is highly modified. Apex of labium flattened into a broad, sclerotised, plate with a three-pronged apex consisting of a large central projection and two, short, lateral projections. Posterior corners of the labium articulating with the tentorial arm. Apex of the tentorial arm also articulating with the mandibles. Mandibles appearing as curved, brown sclerotised rods encased within fleshy, laterally flattened projections that appear at the lateral margins ofthe mouth and are attached to the base of the papillae supporting the antennomaxillary organs. Apices of the labrum and labium slightly but distinctly upcurved. Apodemes supporting labrum strongly sclerotised and extending back almost to the posterior end of the ventral cornu. Ventral cornu with a sclerotised area towards posterior margin. Ventral bridge not strongly sclerotised mid-ventrally. Dorsal cornu narrower and about 0.6 as elongate as ventral cornu.
Thorax: Antero-dorsal margin of pro thorax with pale brown spicules. Apico-Iateral and apico-ventral margins of prothorax papilliate. Lateral lips fleshy, lacking sclerotisation. Anterior spicules at posterior margin of prothorax with 4 openings. Rest of thorax with coriacious transverse bands alternating with clear bands corresponding to where the integument folds during movement. Ventral surface of mesothorax with a pair of raised pads.
Abdomen: Abdominal segments 1-7 with four transverse dorsal folds between which are coriacious transverse bands and no other vestiture. Paired locomotory prominences on abdominal segments 1-7 bearing sensilla 9 and 10. Anal segment: about equally developed dorsally and ventrally with two dorsal and three ventral folds. Apex bearing a pair of bar-like locomotory lobes. Anal opening transverse. Posterior breathing tube: Length 0.58 mm; basal width 0.30 mm; apical width 0.35 mm (n = 2). Base nodulate, smooth and shiny above and bifurcated at apex. Each spiracular plate with ecdysial scar at dorso-Iateral margin, three elongateoval spiracular openings with dark to blackened margins extending over the sides of the spiracular plate and four interspiracular nodules bearing setae, setae often missing.
Puparium (from Weng and Rotheray 2008).
Length 5.8±0.4 mm (n=20). Anterior end inflated and arched dorsally. Integument translucent to mottled with pale and dark brown blotches. Pupal respiratory processes absent. Spiracular openings black margined and interspiracular nodules and spiracular plate mostly black.
The adult and larva of Allograpta micrura Osten Sacken, 1877 (Diptera, Syrphidae) feed on pollen of Castilleja talamancensis Holmgren, 1978 (Scrophulariaceae) in the highlands of Costa Rica. Usually one larva was found inside each C. talamancensis flower or fruiting structure. Larvae use the curved tips of the labrum and labium to pierce the theca and gain access to pollen. Larvae only partially digest pollen grains and do not damage other reproductive organs of the flower during feeding. Larvae require pollen from more than one flower to complete development. Defecation occurs several times prior to pupation perhaps to accommodate the large amount of pollen consumed. Pupation lasted from 9 to 13 days in the laboratory (20 ºC) (Weng and Rotheray 2008).
On first emerging from the egg, first instar larvae remained immobile for several minutes before starting to tunnel through the calyx. They tunnelled by holding the body at a right angle to its surface. Larvae appeared to ingest plant tissue during this process as a dark coloured mass appeared in the gut. Tunnelling lasted for ten minutes or more. Sometimes a larva interrupted tunnelling and moved to start elsewhere for no obvious reason.
Larvae of all stages performed scanning or casting movements by extending and swinging the thorax from side to side. But when the larva touched an anther, casting ceased and the larva pressed its mouth against the theca which appeared to be held in place by sticky saliva. Video tapes revealed subsequent feeding in greater detail than by direct observation. The tips of both the labrum and the labium protruded and pierced the theca. The head skeleton was then moved forwards and backwards repeatedly at a rate of up to 45 times per minute, until the theca was almost emptied of pollen. The larva used its fleshy mouthparts to imbibe the remaining pollen grains before abandoning the anther. A third instar larva took under thirty minutes to imbibe pollen from a fully developed anther.
The frass is bright yellow. This colour is probably due to the oily yellow pigment from the pollenkitt. The same yellow oil pigment was also seen in the fresh pollen, but in larger sized drops. Larvae of A. micrura seemed to feed on the pollenkitt and also a certain amount of cytoplasm in the pollen. Compared to fresh pollen, digested pollen had more visible exine. Cytoplasmic material also seemed to be reduced after passing through larval guts (the pollen absorbed less blue dye) and ruptured pollen was only found in digested samples. Less than 10 % of digested grains were ruptured and most showed had a reduced density of cytoplasmatic material compared with fresh samples.
In the laboratory, larvae occasionally ingested flower and calyx tissues and also decaying leaves, particularly when not supplied with pollen. These tissues were easily identified inside larval guts as dark coloured masses that contrasted with the bright yellow pollen mass. No evidence of larval predation on aphids or adult flies was obtained. Apparent contacts with aphids or adult flies did not elicit predation. Occasionally a larva struck out against an aphid or fly with its mouthparts and left it coated with a blob of saliva, a known defence of syrphine larvae (Rotheray 1993).
Second instar larvae defecated at least once prior to moulting. Third instar larvae defecated at least once prior to pupation. Larvae emptied all gut contents each time. Moulted skins bearing the head skeleton were found close to the frass inside flowers, both in the field and in the laboratory. Second stage larvae started feeding immediately after moulting. Bright yellow frass was also left inside flowers after feeding. Third instar larvae maintained in the laboratory defecated shortly before abandoning the host flowers to pupate.
unless otherwise stated