Click to enlarge.

Beginner

Scientific Names
Chalcidoids are members of a very large and diverse group of wasps, most of which parasitize other insects. Species include Aphelinus mali Haldeman (Family Aphelinidae), Trichogramma spp. (Family Trichogrammatidae), and others.

Identification
Members of two families, the Aphelinidae (Aphelinid wasps) and Eulophidae (Eulophid wasps), are more commonly seen in apple orchards, although Trichogrammatidae egg parasitoids may play a significant role as biological control agents. 

Aphilinid wasps

Eggs:

• Laid in host aphid.
• Not observed. 

Larvae:

• Elongate and without features.
• Not observed.  
• Parasitized woolly apple aphids are hardened, black and somewhat swollen. 

Pupae:

• Found within parasitized aphids.
• Features such as legs and antennae becoming apparent, black.

Adults:

• Small (0.6-4 mm).
• Yellow, brown or black wasps that lack a metallic appearance. 
• Wasp is slightly smaller than the aphid host in which it lays its eggs.  
• Circular exit holes are cut as it chews its way out of the dead aphid.

Eulophid wasps

Eggs:

• White, cylindrical and laid inside the leafminer mine – the host caterpillar.

Larvae:

• Maggot-like – white, legless and elongate, up to 2.5 mm. 
• Found on the outside of the host leafminer larvae. 

Pupae:

• Recognizable by their mummy-like appearance when mines are opened.
• Dark brown to black.
• 2.5 mm in length, and are more robust than those of the host leafminer caterpillar. 

Adults:

• Small with metallic bodies.
• The host is completely consumed by the developing wasp larva. 
• When mines are opened, all that remains is the wasp pupa and a small, circular hole in the mine through which the new adult escaped.

Trichogramma wasps
Eggs: Laid directly into host insect egg, not observed.
Larvae / Pupae: Develop inside host egg.  Parasitized eggs appear black.
Adults: Minute wasps, 1mm or smaller, with red eyes and yellowish bodies.

Often Confused With
Parasitic wasps are often difficult to distinguishing between each other.  Learn to recognize the signs of parasitism in orchard pests.

Interaction With Host
Despite their small size (most are less than 3 mm in length) many chalcidoids are parasitoids of agricultural pests and are important biological control agents.  Chalcidoids parasitize eggs, larvae or pupae of hosts.  Female wasps lay their eggs on or in the host.  Some larvae feed internally (endoparasitoids) while others attach to the host and feed externally (ectoparasitoids).  The host insect is killed in the process. 

Aphilinid wasps attack scale insects, whiteflies and aphids.  In apple, A. mali is a key parasitoid of the woolly apple aphid. 

Eulophid wasps represent the largest family of chalcidoid wasps. Most species parasitize concealed larvae, especially those inhabiting leaf mines such as the tentiform leafminer. Larvae are ectoparasitoids, meaning they develop externally on the affected hosts. 

Trichogramma wasps parasitize eggs of other insects, particularly those of caterpillars. In apple orchards, Trichogramma spp. parasitize thee eggs of many economic pests such as those of codling moth and leafrollers.  

Insects Attacked
Aphids, caterpillars, flies, scale insects, other.

Monitoring and Management
Chalcidoid wasps are most readily observed as larvae or pupae during monitoring activities for insect pests. Eulophid ectoparasitoids populations should be surveyed following leaf-sampling protocols for tentiform leafminer. Parasitoid larvae, pupae and partially consumed leafminers can be seen using a microscope when mines are opened. A. mali is susceptible to many insecticides and does not provide economic control in most commercial orchards.

Advanced

Scientific Names 
Chalcidoids are members of a very large and diverse group of wasps, most of which parasitize other insects.  Species include Aphelinus mali Haldeman (Family Aphelinidae), Trichogramma spp. (Family Trichogrammatidae), Colpoclypeus florus (Family Eulophidae).

Identification
Members of two families, the Aphelinidae (Aphelinid wasps) and Eulophidae (Eulophid wasps), are more commonly seen in apple orchards, although Trichogrammatidae egg parasitoids may play a significant role as biological control agents. 

Aphilinid wasps

• Eggs: Laid in host aphid, not observed. 
• Larvae: Elongate and without features, not observed.  Parasitized woolly apple aphids are hardened, black and somewhat swollen. 
• Pupae: Found within parasitized aphids, features such as legs and antennae becoming apparent, black.
• Adults: Aphelinid adults are small (0.6-4 mm) yellow, brown or black wasps that lack a metallic appearance. The adult wasp is slightly smaller than the aphid host in which it lays its eggs. Circular exit holes are cut by the adult parasite as it chews its way out of the dead aphid.

Eulophid wasps

• Eggs: White, cylindrical and laid inside the leafminer mine – not inside the host caterpillar.
• Larvae: Maggot-like – white, legless and elongate, up to 2.5 mm.  Found on the outside of the host leafminer larvae. 
• Pupae: When mines are opened, pupae are recognizable by their mummy-like appearance.  Distinct body regions including the head thorax, and abdomen, and eyes, antennae, are readily discernable.  Pupae are dark brown to black, 2.5 mm in length, and are more robust than those of the host leafminer. 
• Adult: Small with metallic bodies. The host is completely consumed by the developing wasp larva.  When mines are opened, all that remains is the wasp pupa and a small, circular hole in the mine through which the new adult escaped.

Trichogramma wasps

• Eggs: Laid directly into host insect egg, not observed.
• Larvae / Pupae: Develop inside host egg.  Parasitized eggs appear black.
• Adults: Minute wasps, 1mm or smaller, with red eyes and yellowish bodies.

Often Confused With
Parasitic wasps are often difficult to distinguishing between each other.  Learn to recognize the signs of parasitism in orchard pests.

Interaction with Host
Despite their small size (most are less than 3 mm in length) chalcidoids are parasitoids of agricultural pests and are important biological control agents. Chalcidoids parasitize eggs, larvae or pupae of hosts.  Most are specialized and many have very specific hosts.  Female wasps lay their eggs on or in the host.  Some larvae feed internally (endoparasitoids) while others attach to the host and feed externally (ectoparasitoids).  The host insect is killed in the process. 

Aphilinid wasps attack scale insects, whiteflies and aphids.  In apple, A. mali is a key parasitoid of the woolly apple aphid.  Parasitized woolly apple aphids are hardened, black and somewhat swollen. 
There are several generations of A. mali in Ontario.  The parasitoid overwinters as mature larva or pupa inside the dead body of a woolly apple aphid, and emerges in the spring as aerial (above-ground) colonies of woolly apple aphids begin to develop in the orchard.  Female wasps sting the host and lay an individual egg per aphid, and the resulting parasitoid larva feeds internally to complete development. 

Eulophid wasps represent the largest family of chalcidoid wasps.  Most species parasitize concealed larvae, especially those inhabiting leaf mines such as the tentiform leafminer.  Larvae are ectoparasitoids, meaning they develop externally on the affected hosts.  When a eulophid wasp finds a leaf containing tissue-feeding stages of the tentiform leafminer, the female stings the larva and deposits an egg into the mine.   The egg hatches and the larva feeds on the host to complete development.  Female wasps also attack and feed on sap-feeding stages of the tentiform leafminer. The combination of parasitism and adult feeding can provide substantial reductions in tentiform leafminer populations in commercial orchards following IPM programs.  Another species, the introduced eulophid wasp C. florus can provide significant parasitism biological control of obliquebanded leafroller.  This insect is a gregarious ectoparasitoid, meaning multiple individuals are produced from and feed externally on a single larva.

Trichogramma wasps parasitize eggs of other insects, particularly those of caterpillars. In apple orchards, Trichogramma spp. parasitize thee eggs of many economic pests such as those of codling moth and leafrollers.  

Parasitic wasp biology is often synchronized with that of their hosts. 

Insects Attacked
Aphids, caterpillars, flies, scale insects, other.

Monitoring and Management
Chalcidoid wasps are most readily observed as immatures (larvae, pupae) during monitoring activities for insect pests.  Adults are easily disturbed and rarely seen in the field.

Eulophid ectoparasitoids populations should be surveyed following leaf sampling protocols when the majority of leafminer tissue feeders have pupated but prior to any significant moth emergence (first and second generation).  Parasitoid larvae, pupae and partially consumed leafminers can be seen using a microscope when mines are opened.

Look for aphid mummies within aphid colonies. Parasitized woolly apple aphids appear black. A. mali is susceptible to many insecticides and does not provide economic control in most commercial orchards.