The following is a key to insect larvae feeding internally in apple fruit. Characters have been compiled from several sources (given below). Several morphological terms should be reviewed. Caterpillars have six true, jointed legs on the thoracic segements, immediately behind the head. The remaining, abdominal segments have various arrangements of prolegs (fleshy lobes used for grasping). These prolegs have small hooks, or crochets. These crochets may be arranged in a row of hooks of equal length (uniordinal), alternating long and short hooks (biordinal), or alternating long, medium and short hooks (triordinal). When a caterpillar or grub is viewed face-on, there are some sutures or lines on the face that form an inverted "Y". The central area between the arms of the "Y" is called the frons; the area just forward of this region is the clypeus. High magnification is required to examine these structures.

 
• (1a) Head capsule present (See ohoto above); chewing mouthparts .............................2
• (1b) Head capsule absent; anterior end tapers to point with two retractile mouthhooks (Diptera) .............................................11

 
• (2a) Legs present ......................... 3
• (2b) Legs absent (see photo at top of page) (Curculionidae) ................  10

 
• (3a) Prolegs beginning on third or later abdominal segment (Lepidoptera) ............................. 4
• (3b) Prolegs beginning on second abdominal segment (Tenthredinidae; sawflies) ............ 12

 
• (4a) Circle of crochets interrupted at inner part of circle; dark brown larva with black head ......... PEACH TWIG BORER (reported from apple fruit, but uncommon in our area; Univ. of California and British Columbia links)
• (4b) Crochets forming complete circle or interruped at outer part of circle; color otherwise .................................................... 5

 
• (5a) Body color pinkish, especially on dorsal surface; uniordinal crochets are in complete circle (Olethreutinae) ...... 6
• (5b) Otherwise .................................. 9

 
• (6a) Lacking anal comb, length 14-16 mm, head width 1.6 mm, feeds in core and seeds (HYPPZ site)

..........CODLING MOTH, Cydia pomonella (L.)
• (6b) Possessing anal comb, larvae smaller; tend not to feed in core............7

 
• (7a) Crochets 30-40 on ventral prolegs, 20-25 on anal prolegs; length 10.6 mm, head width 1.1 mm; spinneret 7-8.5 times as long as wide

..........ORIENTAL FRUIT MOTH, Grapholita molesta (Busck)
• (7b) Crochets 25-30 on ventral prolegs, 15-20 on anal prolegs; spinneret 5-6 times as long as wide...................................8

 
• (8a) Head yellow-brown, not overlaid with brown; length 9-10 mm, head width 0.72-0.80 mm; plates at base of hairs with reddish pigment on posterior segments

..........LESSER APPLEWORM, Grapholita prunivora (Walsh)
• (8b) Head yellow-brown overlaid with brown, length 8-9 mm, head width 0.77-0.79 mm; plates at base of hairs without reddish pigment on posterior segments

..........CHERRY FRUITWORM, Grapholita packardi Zeller (NCSU Link)
 
• (9a) Brownish-green body, head brown with darker brown overlay; mature length 13-18 mm, head width 1.21 mm

..........TUFTED APPLE BUD MOTH, Platynota idaeusalis (Walker)
• (9b) Light brown to grey-brown body; small plates bearing hairs brown with pale centers; head yellowish to reddish brown; crochets triordinal, with break in outer edge of circle

..........EUROPEAN CORN BORER, Ostrinia nubilalis (Hubner), (Iowa State photo) (Uncommon in apple fruit, but may occur in weedy orchards)
 
• (10a) Oviposition hole associated with crescent-shaped cut; if larvae survive, feeding in flesh of fruit; the posterior dorsal edge of the head capsule notched; central line on frons extends from posterior edge halfway to clypeus; mature body length 8-10 mm

..........PLUM CURCULIO, Conotrachelus nenuphar (Herbst) (Unusual to find live larvae in apple fruit, though ovipositon scars are common)
• (10b) Oviposition hole not associated with crescent-shaped cut; oviposition hole extends often to core; larval feeding from wall of cavity outward; the posterior dorsal edge of the head capsule continuously rounded, not notched; central line on frons extends from posterior edge 3/4 of the distance to clypeus; mature body length 4.6-6.3 mm

..........APPLE CURCULIO, Tachypterellus quadrigibbus (Say) (Uncommon) (BC link)
 
• (11a) Moderately sized maggots, about 8 mm; spiracles not on tubercles, no tubercles on posterior end; brown trails meander through flesh

..........APPLE MAGGOT, Rhagoletis pomonella (Walsh)
• (11b) Tiny maggots, 1-2 mm; posterior spiracles on long tubercles on end of abdomen; distinct tubercles on posterior end; usually in injured or rotten fruit

..........VINEGAR OR POMACE FLIES, Drosophila spp.
 
• (12a) Prolegs on abdominal segments 2-7 and 10; head amber (may be uniformly dark brown in early instars) ........ EUROPEAN APPLE SAWFLY, Hoplocampa testudinea (Klug)
• (12b) Prolegs on abdominal segments 2-8 and 10; head with dark stripe running from stemmata (eyes) to rear edge of head capsule; present mainly where dock is common in ground cover

..........DOCK SAWFLY, Ametastegia glabrata (Fallen) (New York link)

 
• Ahmad, M and H. R. Burke. 1972. Larvae of the weevil tribe Anthonomini (Coleoptera: Curculionidae). Misc. Publ. Entomol. Soc. Am. 8: 31-81.
• Brooks, F. E. 1924. The cambium curculio, Conotrachelus anaglypticus Say. J. Agric. Res. 28: 377-386.
• Chapman, P. J. & S. E. Lienk. 1971. Tortricid fauna of apple. N.Y. State Agric. Exp. Stn. Spec. Publ. 122 p.
• Garman, P. 1918. A comparison of several species of Lepidoptera infesting peach and apple in Maryland, with additional notes on the oriental peach moth. Md. Agric. Exp. Stn. Bull. 223: 103-126.
• Howitt, A. H. 1993. Common Tree Fruit Pests. Mich. State Univ. Ext. NCR 63. 252 p.
• MacKay, M. R. 1959. Larvae of North American Olethreutidae (Lepidoptera). Can. Entomol. 91 (Suppl. 10): 1-338.
• Stehr, F. W. (ed.) 1987. Immature Insects. vol. 1. Kendall Hunt, Dubuque. 754 p.
• Stehr, F. W. (ed.) 1987. Immature Insects. vol. 2. Kendall Hunt, Dubuque. 974 p.