Weird Insects - Part 4 - Aphids - Deformers and Misshapers

In Part 3, we looked at insects that "defile" or misshape plants through the creation of web nests for feeding, development and protection (and maybe company?).  In this final part, I'll talk about a common group of insects, aphids.  However, we'll look at some of the unusual or unique reactions that we sometimes see in plants from the feeding of different species.

Aphids

Aphids don’t tend to be all that subtle about their feeding.  They are inefficient feeders, basically sucking in the sugar-rich sap from the plant and firing it right out the back end in a pretty similar form (this is according to my simplified understanding).  They feed in big groups, don’t tend to move much and cause mostly localized damage.  That being said, they can cause a pretty dramatic impact on plants.

In some cases, the degree of response will depend on the plant species being attacked.  In the case of this currant, it responds to damage with the production of darker pigments and some weird cellular growth, which looks like red blisters from the top.  Turning over the leaf reveals the many aphids chowing down on the plant.



Conspicuous distortion and discolouration on the upper leaf surface of a currant bush

Severe discolouration and distorted growth of a currant bush

Examination of the leaf underside reveals scores of aphids feeding, which results in the wound reponse (discolouration) and the distortion (feeding injury) - Note the crocodile-like larva of a predatory insect eating out at the all-u-can-eat Aphid buffet (lower left)

Sometimes, the way an aphid feeds on a particular host and the resulting distortion of the plant can be used in identifying the species.  On these elms leaves, we find either the Woolly Apple Aphid, which causes a terminal distortion or the Woolly Elm Aphid, which causes a bit of a leaf rolling effect.  If you open up the roll, you’ll find scores of aphids feeding, with plenty of honeydew pouring out.

Terminal leaf distortion likely caused by an infestation of Woolly Apple Aphids

Distorted leaf growth, likely caused by Woolly Apple Aphid

A rolled leaf edge is the result of feeding injury by Woolly Elm Aphids

Underside of the rolled leaf reveals scores of aphids feeding - honeydew secretions and waxy deposits are also evident

When aphids feed on a more succulent or tender plant, particularly at or near a growing point, you’ll find that the undifferentiated growth their feeding can cause tends to result in distortion of the plant tissues, as viewed on this Larkspur.

Twisted, distorted growth due to severe levels of aphid feeding

Damaged and distorted growth

Sometimes, you find something that is totally freaky, like what these aphids did to this poplar leaf.  Somehow (I have no idea how), they formed a bit of a pocket to feed within.  When you open it up, you find it packed full of aphid-y goodness.  This is close to the weirdest aphid-related thing I’ve ever encountered.

Odd looking swellings along a Poplar leaf vein

Leaf underside showing a pocket-like swelling

Opening of the swelling (from the top side) shows masses of aphids feeding inside

Cooley Spruce Gall Adelgid (Adelges cooleyi)

There are a number of different adelgids, which are distinctly aphid-like.  In this case, this species moves between Douglas fir and Spruce, causing a “pineapple-like” gall on the new growth of spruce trees.  The galls mature with the stages of the insect inside over a period of one or two years.  The insects eventually move back to the Douglas fir to complete the life cycle.  The pictures show mature, empty galls.

Swelling on the new growth of a Spruce caused by infestation by Cooley Spruce Gall Adelgid

Gall/swelling is very old, as evidenced by grey colour of the gall

Two gall/swellings caused by Cooley Spruce Gall Adelgid - open gaps indicate that the insects have left for the alternate host (Douglas Fir)

The opening of one of the swellings shows cavities where the insects lived while developing - some waxy deposits are also visible



Some other types of gall-forming adelgids cause slightly different swellings



Weird Insects - Part 3 - Defilers

In Part 1 and Part 2, we looked at insects that are shelter or protect themselves in unusual ways or in galls to hide themselves during development.  In this part, we'll look at a couple of insects that "defile" and/or create misshapen growth in plants.

Defilers

Some insects create nasty web homes for them to feed and develop within.  They produce silk webbing and tie together leaves and branches to varying degrees, depending on the species.  They go through developmental stages, eat, poop, etc. creating a big pile of grossness.  I would guess that the mess protects them, for the most part, from predators and the environment.  The two examples that I’ve come across are the Ugly Nest Caterpillar (aptly named, I’d say) and another insect on Pine, which I haven’t sorted out yet.  It is equally gross, as it is tough to say what exactly all the stuff you are seeing is.  I’d lean towards poop.  Poop tends to end up nearby, no matter which insect you are dealing with.  Overall, these “defilers” can mess up the shape and form of the tree, as they tend to stick to the new growth of the tree.

Ugly Nest Caterpillar (Archips cerasivorana)

Large number of nests are visible from a distance in a chokecherry shelterbelt

Multiple nests apparent on a single chokecherry bush

Nest of Ugly Nest Caterpillar - masses of webbing ties together branches and leaves to create a place for hundreds of larvae to develop

Big nest of Ugly Nest Caterpillar

Ugly Nest Caterpillar nest - pupal casings, frass (poop) and other debris are visible within the mass

Ugly Nest Caterpillar adult moth

Some sort of nest-creating insect in Pine

Somewhat conspicuous, reddish-brown nest/mass on a Pine tree - it appeared to be approximately 6-12 inches in length



Numerous messy reddish-brown nests can be seen on this large Pine



Weird Insects - Part 2 - Gall-forming insects

In the past article, I discussed insects that hide themselves in unique ways, either through materials they collect or produce themselves.  In this article, I'll look at insects (or insect-like creatures) that hide through stimulation of plant cellular division and enlargement, or through the formation of galls.

Gall forming Insects

Gall forming insects (or things that we call insects incorrectly) lay their eggs into cells or tissue layers, causing a gall to form from plant growth hormones  produced by the plant’s wound response or by the production of the PGHs themselves (or something similar).  Regardless, the plant is stimulated to have a small to massive amount of cell division and enlargement, creating a gall.  In some cases, it is a tiny gall, in others, it is sizeable.  Regardless, it is interesting.

Leaf Gall Mites (different species with the family Eriophyidae)

These tiny pests are not actually insects (closer to spiders), but they lay their eggs in the leaf and a very small, erupted gall forms.  It doesn’t seem to do much damage, other than make things look a bit weird.  Some gall mites can produce quite colourful erupted galls.  Some galls are actually disrupted leaf hairs, with no penetration of the leaf itself.

 

Leaf gall mites on Elm - raised areas are erupted cellular growth, each containing an immature mite



Multiple galls from gall mites on Elm - this may be a different species, as the eruptions/galls are somewhat more rounded than the ones in the above picture

Many, many galls from mite egg laying on Elm

Chokecherry Fruit Gall Midge (Contarinia virginianae)

This insect can actually be quite a pest if the population gets ramped up, but generally it just causes a minor amount of damage to just a few fruit.  The normally pea-sized chokecherry swells to the size of small to medium sized grape, turns bright red (rather than green through to purple), and is full of bright orange wriggling maggoty larvae.  It is pretty revolting, but a vivid example.

Chokecherry Fruit Gall Midge-infested fruit - fruit is enlarged, bright red and a bit misshapen

Several fruit are infested with Chokecherry Fruit Gall Midge on this plant - Note, galls range in size



Heavy infestation of Chokecherry Fruit Gall Midge

Houston, we have a problem - major infestation of Chokecherry Fruit Gall Midge

Opened fruit reveals numerous bright orange larvae wriggling around inside the enlarged fruit



Willow Pine Cone Gall Midge (Rabdophaga strobiloide)

This is one weird looking example of a tiny insect making a big, showy spectacle of its shelter.  The adult is a tiny insect, called a midge.  It lays its eggs right on the tip of the growing point of a terminal (tip) bud or axillary (side shoot) bud.  The damage (and likely subsequent production of growth hormones) causes the plant to produce layers and layers of leaves, resembling a pine cone the size of a golf ball when it is done.  If you unpeel the layers, you’ll find a tiny larva exactly in the middle of the base of the “cone”.  Engineers could learn something from this insect, it is that accurate.  The larva is the size of a grain of rice.

Willow branch with a Pine Cone Gall on the terminal bud

Willow Pine Cone Gall caused by a small midge

Taking apart the gall reveals a tiny white larva at the exact centre of the mass of woody "leaves" that comprise the gall



Tiny white larva in the centre of the gall

Midge larva on the tip of the scalpel blade, having been removed from where it was sitting perfectly upright in the gall

Saskatoon berry cabbage leaf thingy from the Peace

A similar gall was observed on Saskatoon berries up in the Peace region of Alberta.  At the time, I had no idea what to make of it.  I still have no idea, but odds are, it is something similar.

Tiny cabbage leaf gall on Saskatoon berry

Bottom view of a gall on Saskatoon berry

Willow Red Gall (Pontania proxima)

Some insects lay their eggs into the leaves, resulting in a discoloured swollen area of cells, which protects the insect through its development.  In the case of this gall on willow leaves, it looks like big, hard, red lumps or blisters, but starts off as a green lump.  The immature insect is embedded deep inside the gall.  The insect is a type of sawfly, called the Willow Redgall Sawfly.

Golden Willow appears to have a bad case of "the spots"

Red swellings/galls on the leaves of Golden Willow



Galls protrude both above and below the leaf surface

Galls on willow leaves can be opened to reveal "critters"

Very small larvae were observed at the heart of the gall

Similar galls can form on the stems or branches of different species.  In this case, on willow, the hard little lumps could be seen underneath the growing point or at or near buds.  The larva was pretty small, which seems typical of many gall-forming pests.  I’m not sure of the cause.

Woody gall on the stem of a different species of willow

Removed and dissected gall reveals a small, orange larva inside

Orange speck is the larva of the gall-forming insect - it was about half the size of a grain of rice

Stem Galls

Sometimes, galls can be quite dramatic when they form on stems or trunks of trees.  If the gall develops enough, the plant could potentially be girdled (vascular system blocked) resulting in death of the plant or at least a severely stunted plant.   In the following pictures, from a grafted willow, the galls were the size of a small-ish apple and when I dug away at them, I found the pupal casing (protective developmental covering) of some sort of insect.

Large gall swellings on the trunk of a grafted willow - they were about the size of small apples (2-3 inches across)

Opened gall shows strange cellular growth

Pupal casing found inside the gall - this is where the insect developed for a period of time before emerging

Pupal casing removed from the gall - the approximate size was 1/4 to 1/2 inch in length