Tiger swallowtail the size of a sulfur

[mothman55]

Got this tiny tiger (Papilio canadensis) last June in Southern Ontario. It has a 2" wingspan. Smallest I have ever come across.

[Adam Cotton]

Amazing, I have never seen one that small before. If the larva was starved it is amazing that it actually completed development.

Adam.

[joachim]

The caterpillar will only have been L2

[Adam Cotton]

I very much doubt that. It would have been starved at early L5 and formed a minute pupa compared to normal. A larva that doesn't get past L2 can't pupate, it would just die.

Adam.

[Adam Cotton]

By the way, after an L4 larva moults to become L5 it is very small compared to the full grown L5 before normal pupation.

Here is a quite early L5 Papilio polytes larva:



and here is a pretty much full grown L5:



You can see the size difference by comparing the leaves, but immediately after moulting from L4 the larva is about 1/3 as long as when fully grown.

Adam.

[exoticimports]

Astonishing. I have dwarf cecropia and urvilleanus and victoriae, but never seen any dwarf tiger.

Chuck

[joachim]

Apr 3, 2021 14:31:09 GMT -8 Adam Cotton said:

I very much doubt that. It would have been starved at early L5 and formed a minute pupa compared to normal. A larva that doesn't get past L2 can't pupate, it would just die.

Adam.

So what is the explanaion? I also hae some dwarfs but not such extreme.

[Paul K]

Apr 3, 2021 14:51:45 GMT -8 joachim said:

Apr 3, 2021 14:31:09 GMT -8 Adam Cotton said:

I very much doubt that. It would have been starved at early L5 and formed a minute pupa compared to normal. A larva that doesn't get past L2 can't pupate, it would just die.

Adam.

So what is the explanaion? I also hae some dwarfs but not such extreme.

In the last instar larvae consume most of the food plants, perhaps if too many get to that stage, the plant is defoliated and no more nearby that could be a reason.

[leptraps]

When I was rearing Colias I would occasionally have a "mini" an extremely small individual. I have had several very small larva that would pupated but no adult would emerge. No adult parasites would emerge ether.

While living in South Florida I reared some big sphinx moths. The largest were Pseudosphinx tetrio. They also produced the Largest parasitic fly (Diptera) with a gold Abdomen. 24 karrot.

[Adam Cotton]

Apr 3, 2021 15:55:27 GMT -8 Paul K said:

In the last instar larvae consume most of the food plants, perhaps if too many get to that stage, the plant is defoliated and no more nearby that could be a reason.

Sometimes females lay an egg on a very small seedling, which would normally grow sufficiently at the right time of year to feed one larva to pupation. That is why most Papilio species, except the ones with gregarious larvae, normally only lay one egg per plant, a few more if the plant is large. They often like to lay on small plants because those usually have a fast growing tip that the larva can eat when small. If for some reason the plant becomes defoliated or doesn't grow normally the larva can starve at L5, which as Paul K said is when they eat the vast majority of leaves. Sometimes too many females lay one egg each on a small plant, and the youngest larva may not have enough food if the others strip the plant.

Adam.

[wingedwishes]

The butterfly farm in Belize (Green Hills Butterfly Ranch) sends me some Morpho peleides where sone are much smaller. I know they keep them enclosed and fed. Food is not the issue there. Anecdotally, there are aquarium fish that grow very slowly when in a dense population. GIH is suspected to be produced by some fish possibly to slow growth and prevent too large of a biomass in a pond or aquarium. Can larval insects do the same?

[papiliotheona]

Apr 3, 2021 14:31:09 GMT -8 Adam Cotton said:

I very much doubt that. It would have been starved at early L5 and formed a minute pupa compared to normal. A larva that doesn't get past L2 can't pupate, it would just die.

Adam.

It is also possible it was diseased and that compromised the larva's growth/absorption or appetite. CPV or granulosis virus cause malabsorption of the larval gut, i.e. "caterpillar celiac" so the caterpillar eats but gets nothing out of its diet.

[Adam Cotton]

Apr 7, 2021 8:29:15 GMT -8 wingedwishes said:

The butterfly farm in Belize (Green Hills Butterfly Ranch) sends me some Morpho peleides where sone are much smaller. I know they keep them enclosed and fed. Food is not the issue there. Anecdotally, there are aquarium fish that grow very slowly when in a dense population. GIH is suspected to be produced by some fish possibly to slow growth and prevent too large of a biomass in a pond or aquarium. Can larval insects do the same?

One major reason why bred butterflies are often smaller than wild ones is due to overcrowding. As I mentioned above, where larvae are naturally solitary the mother lays only one or two eggs per plant, maybe more if it's a large tree. This ensures that each larva not only has enough food, but the leaves of the correct texture and age for each instar without having to move very far. Basically the larval stage is a race against the clock. The larva needs to eat as much as possible in the permitted time, and when the alarm goes off it must pupate regardless of whether it has eaten enough or not. If the leaves are not ideal it will become smaller than normal, and if it has to waste eating time moving a long way to find the right leaves or moving often that reduces eating time and thus the amount of leaves it can eat.

For solitary larvae, whenever they meet another larva they waste time interacting, and again moving instead of eating. In farm conditions the larvae are kept in unnaturally high density, and the number of times that larvae disturb each other is way more frequent than in nature. Also if large and small larvae are reared together the smaller larvae will not compete and be stunted adults as a result. I recommend only ever keeping the same size larvae on a plant if you cannot separate them one per plant. Of course this does not apply to gregarious larvae, although they would alsways naturally be the same size as they all came from the same egg batch.

Adam.

[trehopr1]

While under-sized examples of butterflies are not unusual
necessarily under breeding (type) conditions or circumstances;
they are something of an "anomaly" under natural occurring
conditions.

In fact, in all my years of field experiences I have only
encountered natural occurring "mini's" on perhaps 4 or 5
occasions. They are unique (in this way) so one could compare
them somewhat to finding a really nice wild collected aberration.

Off the top of my head, I have wild collected a "mini" Actias luna
(male), a "mini" Colias eurytheme (female), and have sighted a
"mini" Nymphalis antiopa which got away from me.

However, here is yet another which did not get away -- from a friend !

This "mini" Papilio cresphontes (female) was collected by a good
friend/collector in Wisconsin just a few years ago. I acquired it
from him in a trade deal we had. Smallest one he ever recalled seeing...



The above (male) is of typical size for the species. Females
are generally at LEAST the same size but, are usually larger.

As mentioned, this (female) was wild collected, ex pupa, and
seemingly perfectly developed in every way -- just on the small
size of around 4 1/4 inches.

[Paul K]

This is my mini wild collected Catopsilia pomona pomona female.
I collected it in Chiang Mai in my garden. At first when I saw it perching on the tree branch I thought it was Colias fieldii fieldii which is quite rare in Thailand and its been recorded only at the very northern Thailand near at the Myanmar border. to my disappointment it was only this very common species although in very uncommon size.